userver(1)                                                          userver(1)



NNAAMMEE
       userver - Micro-server
       (A fairly simple web server designed for experimentation)

SSYYNNOOPPSSIISS
       uusseerrvveerr

       [--AA|----aacccceeppttss--oonnllyy|----cclloossee--aafftteerr--aacccceepptt]   [--BB|----bblloocckk--ffoorr--sseenndd__eevveennttss]
       [--CC|----ccaacchhiinngg--oonn]    [--DD|----ddeebbuugg--mmaasskk     _[_0_x_]_N]     [--EE|----sseenndd--eevveennttss]
       [--FF|----rreesseett--oonn--cclloossee]  [--GG|----uussee--ggeettppiidd]  [--HH|--hh|--??|----hheellpp]  [--II|----rrccvv--
       ssoocckk--llooww--wwaatt  _N]  [--JJ|----ssnndd--ssoocckk--llooww--wwaatt  _N]  [--KK|----kkddeebbuugg--mmaasskk  _[_0_x_]_N]
       [--LL|----ffuullll--rreeaadd  _N]  [--MM|----mmuullttii--aacccceepptt] [--NN|----sseenndd--lloooopp] [--OO|----sseelleecctt--
       ttiimmeeoouutt _N] [--PP|----ccoouunntt--ssiiggppiippeess] [--QQ|----eeccbb--hhii--wwaatteerr _N] [--RR|----rreeaadd--ssoocckk--
       bbuuff--ssiizzee  _N]  [--SS|----ddoonntt--iinnttrr--sseelleecctt]  [--TT|----ppoorrtt _N] [--UU|----aauuttoo--aacccceepptt]
       [--VV|----uussee--sseennddffiillee]  [----aauuttoo--aacccceepptt--aappeerrttuurree]  [--WW|----wwrriittee--ssoocckkbbuuff--ssiizzee
       _N]    [--YY|----sseenndd--iioo--eevveennttss]    [--ZZ|----ccoonntteenntt--ttyyppee]    [--aa|----aassyynncc--mmooddee]
       [--bb|----eeccbb--bbuuff--eennttrriieess _N] [--cc|----mmaaxx--ccoonnnnss _N] [--dd|----ddeellaayy _N] [--ee|----eexxttrraa--
       aacccceeppttss  _N]  [--ff|----mmaaxx--ffddss _N] [--gg|----aacccceepptt--oonn--cclloossee] [--ii|----iinntteerraaccttiivvee]
       [--jj|----kkeerrnneell--iinnffoo]    [--kk|----ssiiggiioo--uussee--pprrooccmmaasskk]    [--ll|----lliisstteennqq     _N]
       [--mm|----aacccceepptt--ccoouunntt _N] [--nn|----nnoo--aacccceeppttss|----lliisstteenn--oonnllyy] [--oo|----pprroocceessss--ffdd--
       oorrddeerr  [uupp|ddoowwnn|wwrriitteess--ddoowwnn|wwrriitteess--uupp|llrruu|lliiffoo|ffiiffoo]]]  [--pp|----pprrooccss   _N]
       [--qq|----eeccbb--llooww--wwaatteerr  _N]  [--rr|----eeaaggeerr--rreeaaddss] [--ss|----ccoonnnnss--iinn--sseerrvveerr--lloooopp]
       [--tt|----ffrreeee--ffdd--tthhrreesshhoolldd  _N]   [--uu|----ttrraacckk--mmaaxx--ffdd   _N]   [--vv|----uussee--ppoollll]
       [--ww|----eeaaggeerr--wwrriitteess] [--xx|----ssiiggiioo--aacccceeppttss] [--yy|----mmeemmccppyy] [--zz|----rreejjeeccttiioonn--
       rraattee] [--11|----uussee--eeppoollll] [--22|----uussee--eeppoollll22] [--33|----uussee--eeppoollll--ccttllvv]  [----ccffgg--
       ffiilleennaammee _p_a_t_h] [----cclloossee--aafftteerr--ssoocckk--iinniitt] [----cclloossee--aafftteerr--rreeaadd] [----cclloossee--
       aafftteerr--ppaarrssee]    [----sseenndd--ppoollllss--ffoorr--aacccceeppttss]    [----ccaacchhee--ttaabbllee--ssiizzee    _N]
       [----ccaacchhee--mmaaxx--bbyytteess  _N] [----ccaacchhee--mmaaxx--ffiillee--ssiizzee _N] [----ccaacchhee--mmaaxx--llooaadd--ffaacc--
       ttoorr _N]  [----ccaacchhee--lloocckk--ppaaggeess]  [----ccaacchhee--ttaabbllee--pprriinntt]  [----ccaacchhee--ffoorr--ssppeecc]
       [----ccaacchhee--wwaarrmm==ppaatthh]  [----ttrraaccee--ssuummmmaarryy]  [----ttrraaccee--ssuummmmaarryy--oonnllyy]  [----uussee--
       ttccpp--ccoorrkk] [----uussee--mmaaddvviissee] [----uussee--aacccceepptt--sseenndd]  [----iipp--aaddddrr  _N_._N_._N_._N_[_:_P_]]
       [----uussee--aaiioo--aacccceepptt] [----uussee--aaiioo--rreeaadd] [----uussee--aaiioo--wwrriittee] [----uussee--aaiioo--cclloossee]
       [----uussee--ssoocckkeett--aaiioo] [----uussee--aaiioo--wwaaiitt] [----aaiioo--rreeaadd--bbeeffoorree--aacccceepptt]  [----aaiioo--
       rreeaadd--bbeeffoorree--wwrriittee]   [----aaiioo--wwrriittee--eevveennttss--lliimmiitt  _N]  [----aaiioo--rreeaadd--eevveennttss--
       lliimmiitt _N] [----aaiioo--aacccceepptt--eevveennttss--lliimmiitt _N] [----aaiioo--aacccceepptt--tthhoolldd  _N]  [----aaiioo--
       ccoommppllqq--ccoouunntt  _N] [----ppiidd--ffiilleennaammee _p_a_t_h] [----ttrraaccee--ffiilleennaammee _p_a_t_h] [----rreeaadd--
       bbuuffffeerr--ssiizzee _N] [----rreeppllyy--bbuuffffeerr--ssiizzee _N]  [----ddyynn--bbuuffffeerr--ssiizzee  _N]  [----nnuumm--
       ddyynn--bbuuffffeerrss  _N]  [----nnuumm--ddyynn--bbuuffffeerrss--ppeerr--aapppp  _N] [----nnuumm--ddyynn--bbuuffffeerrss--ppeerr--
       aappppsseerrvveerr _N] [----ddyynn--lloocckk--ppaaggeess]  [----ddyynn--ttoouucchh--ppaaggeess]  [----ssttaattss--iinntteerrvvaall
       _N]  [----iiggnnoorree--ffdd--sseettssiizzee]  [----uussee--ccppuu--mmaasskk  _[_0_x_]_N] [----iiddllee--tthhrreesshhoolldd _N]
       [----ddoocc--rroooott _p_a_t_h]  [----hhoossttnnaammee  _n_a_m_e]  [----aapppp  _u_r_i_,_t_y_p_e_[_,_p_a_t_h_[_,_c_o_u_n_t_]_]]
       [----ssttaarrtt--aapppp--sseerrvveerr  _p_a_t_h_[_,_c_o_u_n_t_]_[_=_e_x_e_c___s_t_r_i_n_g_]]  [----aapppp--rreeqq--qquueeuuee--ssiizzee
       _N] [----sskkiipp--hheeaaddeerr] [----vviiccttiimm _f_i_l_e_p_a_t_h] [----vviiccttiimm--sskkiipp _N_] [----ccaacchhee--mmiissss--
       sskkiipp _N_] [----ccaallll--ssttaattss _N_]


DDEESSCCRRIIPPTTIIOONN
       uusseerrvveerr  is  a  micro web server that is meant to be used to experiment
       with the design and implementation of web servers.  In  particular  the
       original  intention was to permit experimental comparisons of different
       event dispatch mechanisms within the same application  framework.   For
       this  reason  there are lots and lots and lots of parameters.  They are
       mainly used to control the behaviour of the server.

       Some of the design philosophy and experimental results  obtained  using
       this  server  are  described in [Brecht-2001].  One of note is that all
       data structures are allocated at initialization  and  are  not  resized
       (grown).  This helps to ensure that experiments can be repeated because
       with dynamic sizing of data structures different loads could result  in
       different server behaviour.

       The  userver uses an event driven architecture.  The idea is to run one
       event driven server per processor.  If using sendfile on Linux the file
       system buffer cache will be shared across all servers. For high-perfor-
       mance one would want to use sendfile since  it  doesn't  involve  extra
       copying from the file buffer cache to socket buffers (i.e., it's a zero
       copy implementation).


       IIMMPPOORRTTAANNTT:: This micro web server is not meant to be  a  full-blown  web
       server.  It is specifically designed for conducting performance experi-
       ments.  For that reason design decisions were made in favour of produc-
       ing repeatable experiments.


EEXXAAMMPPLLEESS
       userver
              This starts the uusseerrvveerr with all of its default options.


       userver --max-conns 300 --accept-count 25
              This  command  causes  the uusseerrvveerr server to limit the number of
              simultaneous connections to 300.  When an event indicating  that
              a  new  connection  is  requested  accept is called continuously
              until either 25 new connections are accepted, or  there  are  no
              more outstanding connections.


       userver --max-conns 300 --accept-count 0
              This  command  causes  the uusseerrvveerr server to limit the number of
              simultaneous connections to 300.  When an event indicating  that
              a  new connection is requested accept is called repeatedly until
              there are no more outstanding connections.  (Note that --accept-
              count=0  means  an infinite number of connections, i.e., no lim-
              its).


       userver --ip-addr 192.168.10.105 --max-conns 300 --listenq 128

       userver --ip-addr 192.168.20.105 --max-conns 300 --listenq 128
              This will start up two copies of the userver each accepting con-
              nections from a different interface.


       userver --ip-addr 192.168.10.105:6801 --max-conns 300 --listenq 128

       userver --ip-addr 192.168.20.105:6802 --max-conns 300 --listenq 128
              Same  as  above except one listens on port 6801 and the other on
              port 6802.


       userver --port 6800 --max-conns 300 --listenq 128
              This command causes uusseerrvveerr to listen  for  incoming  connection
              requests on port 6800.  It uses a listen queue of length 128 and
              it will permit up to 300 simultaneous connections.   Once  there
              are  300  open  connections  it  will not accept new connections
              until an existing connection is closed.


       userver --port 6800 --max-conns 300 --listenq 128 --use-poll
              This is the same as above except using  _s_e_l_e_c_t_(_)  calls  to  get
              events the uusseerrvveerr will use _p_o_l_l_(_)_.


       userver --port 6800 --max-conns 300 --listenq 128 --use-epoll
              This  is  the  same  as  above  except using _p_o_l_l_(_) calls to get
              events the uusseerrvveerr will use _e_p_o_l_l_(_)_.


       userver   -C    --cache-table-size=10000    --cache-max-bytes=262144000
       --cache-max-file-size=1048576
              Caching is turned on.  Caching parameters limit  the  number  of
              files that are cached to 10000, the total number of bytes cached
              to 250 MB, and the size of the largest file that can  be  cached
              to 1 MB.


OOPPTTIIOONNSS

       The operation of uusseerrvveerr can be controlled through a number of options.
       The tool supports  both  short  (one-character)  and  long  (arbitrary-
       length) option names.  Short options are prefixed with a single leading
       dash (-), long options with a double-dash (--).  Multiple short options
       can  be grouped together (e.g., ``--rrww'' is equivalent to ``--rr --ww'') and
       long options can be abbreviated so long as they remain unique.  Parame-
       ters  to  options  can be specified either by following the long option
       name with an equal sign and the parameter value (e.g., ----ppoorrtt==66880000)  or
       by  separating  the option name and value with whitespace (e.g., ----ppoorrtt
       66880000).


OOPPTTIIOONNSS ((GGEENNEERRAALL))
       ----iiddllee--tthhrreesshhoolldd==N
              In a situation where the number of open connections has  reached
              the  limit  (see  --max-conns), the userver will close the least
              recently used connection if it has not seen activity in the last
              N seconds.


       ----uussee--ccppuu--mmaasskk== [[00xx]]NN
              On  systems  that  support  the _s_c_h_e_d___s_e_t_a_f_f_i_n_i_t_y_(_) system call,
              specifies a mask of schedulable CPUs for  the  userver  process.
              If  prefixed with '0x', the argument is interpreted as hexadeci-
              mal; otherwise it is interpreted as decimal.  The least signifi-
              cant  bit  corresponds  to the first logical processor number on
              the system.


       --ff NN

       ----mmaaxx--ffddss==_N
              The maximum number of open file descriptors permitted.  I  can't
              recall  if  this  is  actually  enforced  but it is used to size
              internal data structures.  Note that  there  is  a  relationship
              between  ----mmaaxx--ccoonnnnss  and  ----mmaaxx--ffddss..   If  files  are not being
              cached you could (in the extreme case) have one fd used for  the
              socket  connection  and  one  fd used for the open file.  So one
              needs to set ----mmaaxx--ffddss = more than 2 x  ----mmaaxx--ccoonnnnss..   Note:  it
              should  be  greater because of some descriptors that are used up
              by stdin, out, err, and a few open files, etc.


       --mm NN

       ----aacccceepptt--ccoouunntt==_N
              Call accept repeatedly until  either,  ----mmaaxx--ccoonnnnss  is  reached,
              aacccceepptt(())  returns  EWOULDBLOCK,  or  _N new connections have been
              accepted.  Note that the value of _N can make a substantial  dif-
              ference  in  the  performance of event dispatch mechanisms under
              heavy loads.  See [Brecht-2001].


       --TT NN

       ----ppoorrtt==_N
              Specify the port number that the server should listen  for  con-
              nections on.


       --ll NN

       ----lliisstteennqq==_N
              Specify  the  length  of  the  application's listen queue.  This
              specifies how many connection requests are allowed to be  queued
              in the application before the kernel rejects incoming connection
              requests.  WARNING: on all version of Linux I've ever  seen  (up
              to and including several 2.6.5) the kernel silently converts any
              values of N that are greater than 128 to 128.  For  details  see
              sys_listen and the value of SOMAXCONNS.


       --LL[1 | 2]

       ----ffuullll--rreeaadd==[1 | 2]
              Affects  how calling read works.  If this is set to 1 the server
              will loop on reading the socket  until  the  read  fails.   This
              mainly  happens  either  because  there  is nothing left to read
              because the other end has been closed or  until  it  would  have
              blocked (EWOULDBLOCK).

              If  a  value  of  1 is used the loop on reads will only occur on
              calls to read that occur as a result of an event indicating that
              the first read should be done.  If a value of 2 is used the loop
              on reads occur as above but if ----eeaaggeerr--rreeaaddss  is  also  set  the
              server  will  loop on eager reads (i.e., those that will be done
              immediately following a the acceptance and setup  of  a  connec-
              tion).


       --HH

       --hh

       --??

       ----hheellpp Print out the usage message.


       --MM NN

       ----mmuullttii--aacccceepptt==_N
              Use  the  _m_u_l_t_i_a_c_c_e_p_t_(_)  system  call to perform accepts.  NOTE:
              this was a system call that we added to and experimented with in
              Linux.   The  idea  here is that since we are repeatedly calling
              _a_c_c_e_p_t_(_) to accept a bunch of connections,  why  not  provide  a
              system  call  that allows up to a maximum of _N connections to be
              accepted in one system call.


       --SS

       ----ddoonntt--iinnttrr--sseelleecctt
              Disable asynchronous event notification when  calling  _s_e_l_e_c_t_(_)_.
              I  believe  that  this was initially meant to work for SIGIO and
              for SEND.


       --dd NN

       ----ddeellaayy==_N
              The idea was to introduce a delay that might simulate work being
              done  by  the  server  (like  some  computation and/or a dynamic
              request).  I couldn't find a good  method  for  delaying  for  a
              specified  amount  of time (note that it should be small) with a
              enough accuracy.


       --ee NN

       ----eexxttrraa--aacccceeppttss==_N
              While in the middle of processing events that have been obtained
              (e.g.,  from  select, or some other mechanism) periodically poll
              for new connection requests.  In this case every time _N descrip-
              tors  are  processed we check for new connection requests.  Note
              that this open was never used effectively.  I found it easier to
              use and tune the ----aacccceepptt--ccoouunntt option.


       --gg

       ----aacccceepptt--oonn--cclloossee
              When  a  connection is closed check to see if there are any out-
              standing connection requests.  Note: that this  only  occurs  if
              the  maximum  number of connections was reached and now a closed
              connection will reduce the number of  connections  below  ----mmaaxx--
              ccoonnnnss..


       --oo [[uupp||ddoowwnn||wwrriitteess--ddoowwnn||wwrriitteess--uupp||llrruu||lliiffoo||ffiiffoo]]

       ----pprroocceessss--ffdd--oorrddeerr
              [up|down|writes-down|writes-up|lru|lifo|fifo]

              Change  the  order  in which file descriptors are handled.  They
              are numbered from 0 to _N so the options are:

              up:    from 0 to N

              down:  from N to 0

              writes-down:
                     to writes from N to 0, then reads from N to 0

              writes-up:
                     to writes from 0 to N, then reads from 0 to N

              lru:   least recently descriptor touched first

              lifo:  first descriptor (connection) added to the set first

              filo:  first descriptor (connection) added to the set last


       --pp NN

       ----pprrooccss==_N
              Start _N copies of the server.  Note that this option hasn't been
              tested in a long time and is almost certain to cause problems.


       --ss

       ----ccoonnnnss--iinn--sseerrvveerr--lloooopp
              Add an additional poll for new connections each time through the
              server loop.


       --tt NN

       ----ffrreeee--ffdd--tthhrreesshhoolldd==_N
              When the maximum number of connections  ----mmaaxx--ccoonnnnss  is  reached
              the  server  stops  checking  for  incoming  connections.   This
              options controls when the  server  starts  checking  again.   It
              starts  checking  again  after _N connections can be accommodated
              before reaching ----mmaaxx--ccoonnnnss..


       --uu

       ----ttrraacckk--mmaaxx--ffdd
              The server currently keeps track of the maximum fd ever used and
              uses  that  as  a  parameter  to calls like select.  This option
              implements code to dynamically keep track of  the  maximum  file
              descriptor  currently  used.   Note  that this requires a bit of
              extra processing but it's probably not noticeable, especially if
              it can save extra overhead on copying fdsets and processing time
              in event mechanisms (e.g., select).


       --rr

       ----eeaaggeerr--rreeaaddss
              try to eagerly read from new connections.  Call _r_e_a_d_(_) to try to
              read  the request as soon as the new connection is accepted.  In
              this mode the server optimistically assumes that  data  will  be
              available  for reading when a connection is made on a new socket
              (or very shortly after).  If the assumption  is  incorrect,  the
              read  call simply returns with the error EWOULDBLOCK.  Later the
              event notification mechanism will indicate when  the  socket  is
              readable.


       --ww

       ----eeaaggeerr--wwrriitteess
              try  to  eagerly  perform  writes  to  new  connections when the
              response is available.  Both ----eeaaggeerr--rreeaadd and ----eeaaggeerr--wwrriittee also
              try to take advantage of any potential locality effects by work-
              ing on the most recently used file descriptor and socket.


       --yy

       ----mmeemmccppyy
              Use the mmeemmccppyy library call to copy interest sets before calling
              select.   This  is done rather than doing a straight assignment.
              This exists because the size of the interest set could be  large
              and  I don't know how clever a compiler would be about assigning
              large data structures.  NOTE: it currently copies the side of an
              fd_set.   This should be changed to only copy the amount of data
              required for the maximum fd of interest.


       --zz

       ----rreejjeeccttiioonn--rraattee
              Use the rreejjeeccttiioonn--rraattee is not yet implemented.  The ideas  would
              be  to  specify the frequency with which new connection requests
              should be rejected.


       --VV

       ----uussee--sseennddffiillee
              Use the sseennddffiillee(()) call on systems that have it available.  This
              is only used for uncached files and dynamic content.


       ----uussee--mmaaddvviissee
              Use  _m_a_d_v_i_s_e_(_) calls to provide the kernel with hints that files
              are being read sequentially and when they should  no  longer  be
              cached.


       --vv

       ----uussee--ppoollll
              Use _p_o_l_l_(_) instead of _s_e_l_e_c_t_(_) to get events.


       --11

       ----uussee--eeppoollll
              Use _e_p_o_l_l_(_) instead of _s_e_l_e_c_t_(_) to get events.


       --22

       ----uussee--eeppoollll22
              Use  _e_p_o_l_l_(_) instead of _s_e_l_e_c_t_(_) to get events, but attempt some
              optimizations to reduce the number  of  _e_p_o_l_l___c_t_l_(_)  calls.   We
              found  the  number  of  epoll_ctl  calls to be excessive so this
              options calls epoll_ctl when a new connection is added and  sets
              the  interest  to be READ and WRITE.  This means that epoll_wait
              may return events that we aren't interested  in  (e.g.,  that  a
              socket  is  writable even though we are busy reading) but we are
              exploring the tradeoffs between the two approaches  (--use-epoll
              and --use-epoll2).


       --33

       ----uussee--eeppoollll--ccttllvv
              Use  _e_p_o_l_l___c_t_l_v_(_)  to update events.  This requires the addition
              of a new system call, epoll_ctlv.  This call permits one to col-
              lect  a  bunch of epoll_ctl calls and change interest in a bunch
              of fds  at  once  instead  of  having  to  do  one  system  call
              (epoll_ctl) per change.


       ----ccffgg--ffiilleennaammee ppaatthh
              Read  additional options from a file.  The format of the file is
              the same as the command line, i.e.  long  and/or  short  options
              separated by whitespace (spaces, tabs, linefeeds).  Lines with a
              '#' character in the first column are treated  as  comments  and
              are  ignored.  Config files can use ----ccffgg--ffiilleennaammee to nest other
              config files.


       ----iipp--aaddddrr NN..NN..NN..NN

       ----iipp--aaddddrr NN..NN..NN..NN::PP
              Specify an IP address to listen for new connections on.  Option-
              ally  takes  a  port number P as well.  The special option --ip-
              addr 0.0.0.0 specifies that the userver  should  listen  on  any
              address (this is the default).


       ----ppiidd--ffiilleennaammee ppaatthh
              Sets  the  name of the file where the userver stores its process
              ID number while running.  Specify an empty string ("")  to  sup-
              press  pid  file generation.  If this option is not specified, a
              default value of "userver.pid" is used.


       ----rreeaadd--bbuuffffeerr--ssiizzee NN
              The number of bytes  to  allocate  at  initialization  time  for
              _r_e_a_d_(_) operations on each connection.


       ----rreeppllyy--bbuuffffeerr--ssiizzee NN
              The  number  of  bytes  to  allocate  at initialization time for
              _w_r_i_t_e_(_) operations  on  each  connection  (for  static  requests
              only).



       ----ssttaattss--iinntteerrvvaall NN
              Print  out some simple stats about related to server performance
              at a regularly specified interval.  The interval is specified in
              seconds.   NOTE:  this  options  overrides  the --select-timeout
              option in order to be able to print out stats according  to  the
              selected interval.


       ----iiggnnoorree--ffdd--sseettssiizzee
              If  permitted this causes the userver to ignore limits placed on
              the number of open connections and the maximum values of an open
              file  descriptors that are required when using select (i.e., the
              FD_SETSIZE).  This option does not  work  if  --track-max-fd  is
              defined  or if the event mechanism being used is select or SEND.


       --ZZ

       ----ccoonntteenntt--ttyyppee
              Use heuristics to guess  what  Content-Type  header  to  return,
              based  on  the  uri  from  the request.  For example, if the uri
              ended in ".gif", the userver would  assume  a  content  type  of
              "image/gif".


       ----ddoocc--rroooott ppaatthh
              Set the directory of where to find the documents being server to
              the specified directory.  When the document  root  is  specified
              all  requests are assumed to be relative to the specified direc-
              tory.


       ----hhoossttnnaammee nnaammee
              Set the name of the machine that the userver is running on.   By
              default,  userver  uses _g_e_t_h_o_s_t_n_a_m_e_(_) to determine the hostname.
              The hostname is only used to set the SERVER_NAME  CGI  parameter
              when fulfilling FastCGI requests.



       ----sskkiipp--hheeaaddeerr
              Assume  that  all  files  being  served  contain a header in the
              actual file so there is no need for the server to  generate  and
              send  a header.  Useful for looking at the impact of things like
              cork/uncork when used with sendfile (i.e., if the header  is  in
              the  file  it's one sendfile system call instead of cork, write,
              sendfile, uncork).


       ----ccaallll--ssttaattss NN
              Track statistics for up to N calls/requests.  This  is  designed
              to read the Client-Id: header that we have httperf send in order
              to correlate what is  happening  with  requests  from  different
              clients on different servers.


OOPPTTIIOONNSS ((FFOORR CCOONNTTRROOLLLLIINNGG SSOOCCKKEETTSS))


       --FF

       ----rreesseett--oonn--cclloossee
              Calls _s_h_u_t_d_o_w_n_(_) instead of _c_l_o_s_e_(_)_.
              WARNING do not use this for a real system!!!


       --II NN

       ----rrccvv--ssoocckk--llooww--wwaatt==_N
              Sets  the  sockets  receive  buffer's  low water mark to _N_.  Not
              available on all systems.


       --JJN

       ----ssnndd--ssoocckk--llooww--wwaatt==N
              Sets the sockets send buffer's low water mark to _N_.  Not  avail-
              able on all systems.


       --OO NN

       ----sseelleecctt--ttiimmeeoouutt==_N
              Set the timeout option to the _s_e_l_e_c_t_(_) system call.


       --RR NN

       ----rreeaadd--ssoocckkbbuuff--ssiizzee==_N

       --WW NN

       ----wwrriittee--ssoocckkbbuuff--ssiizzee==_N
              Set  the  size  of  the read or write socket buffers.  Note that
              increasing these may help significantly for large transfers.


       ----uussee--ttccpp--ccoorrkk
              Cork the TCP queue when writing the header for the reply.   Cur-
              rently only implemented for the sendfile portion of the code.



       --cc NN

       ----mmaaxx--ccoonnnnss==_N
              The  maximum  number of simultaneous connections the server will
              handle.  Note that this is typically limited by  the  number  of
              open  file  descriptors  permitted.   Once the maximum number of
              open connections is reached  incoming  connection  requests  are
              refused  until  an existing connection is close.  Note that idle
              connections can be timed out eventually (but  this  hasn't  been
              tested  lately).  This is also used to size a number of internal
              data structures that are allocated at initialization time.


OOPPTTIIOONNSS ((FFOORR SSEERRVVIINNGG DDYYNNAAMMIICC CCOONNTTEENNTT))




       ----aapppp uurrii,,ttyyppee[[,,ppaatthh[[,,ccoouunntt]]]]
              Define  an  application.   Applications  are  used  to  generate
              dynamic  content.   An application is uniquely identified by the
              uri string, which is case sensitive.  The  type  string  is  not
              case sensitive, and can be one of

              FastCGI:
                     General-purpose FastCGI application.

                     The  path  argument  specifies the address of a listening
                     FastCGI application, in the form of either an INET domain
                     socket  address  (addr:port)  or  a  UNIX  domain  socket
                     address (file path).  The optional count argument can  be
                     specified  with  INET  domain socket addresses to specify
                     that count consecutive ports, starting with port, are all
                     listening  FastCGI  applications.   It  is  a shortcut to
                     specifying them individually using multiple  --app  argu-
                     ments.

              SPECweb99:
                     SPECweb99  server  application (only available if support
                     is compiled in).  The userver will treat requests of  the
                     specified  uri  as  SPECweb99 requests, and will generate
                     responses on the fly.

                     The path and count arguments are not applicable and  must
                     be omitted.


       ----ssttaarrtt--aapppp--sseerrvveerr ppaatthh[[,,ccoouunntt]][[==eexxeecc__ssttrriinngg]]
              Tell   the   userver  to  start  up  the  specified  application
              server(s).  (By default, userver assumes that they  are  already
              started  through  some  other  means, e.g. manually or through a
              script).  The path and optional count arguments are as described
              for  the ----aapppp option, above.  It is an error to try to start up
              any application servers that  aren't  defined  using  the  ----aapppp
              option.   The optional exec_string argument is a string suitable
              for passing to execl() to start the application server(s).  Note
              that if exec_string contains spaces or shell metacharacters, you
              will have to enclose it in quotes and/or escape those  metachar-
              acters  in order for the string to be seen correctly by userver.
              If exec_string is omitted, then it is inferred  by  interpreting
              the  uri in the corresponding application as an actual directory
              path rooted at the document root (see the ----ddoocc--rroooott option).


       ----aapppp--rreeqq--qquueeuuee--ssiizzee NN
              The number of queue  spaces,  per  application  (see  the  ----aapppp
              option  above),  to reserve for dynamic requests.  Requests need
              to be queued  whenever  an  application  server  or  some  other
              resource  (such as dynamic buffer space, see above) is temporar-
              ily unavailable.  Should the request  queue  ever  become  full,
              userver  will  respond  to  arriving  requests  with an HTTP 503
              error.  If not specified, this option takes on the same value as
              ----mmaaxx--ccoonnnnss so that it is effectively impossible to overflow the
              request queue.



       ----aapppp==AAPPPP,,PPRROOTTOO,,HHOOSSTTNNAAMMEE::PPOORRTT,,NNUUMM
              Registers one or more application servers with the userver. This
              means  that  dynamic  requests  for APP will be forwarded to the
              application server(s) running on HOSTNAME and listening on PORT.
              The  optional  NUM  argument specifies the number of application
              servers running on HOSTNAME. When NUM is greater than  one,  the
              application  servers  listen on consecutive ports, starting with
              PORT. The PROTO flag specifies the communication protocol.  Cur-
              rently, only the FASTCGI protocol is supported. Here is an exam-
              ple:

              ----aapppp==ssppeeccwweebb9999--ffccggii..ppll,,FFAASSTTCCGGII,,llooccaallhhoosstt::99000000,,2244

              In this example, dynamic requests for the specweb99-fcgi.pl  are
              handled by 24 application servers running on the same machine as
              the userver. These application servers are  listening  on  ports
              9000  - 9023, and communicate with the userver using the FASTCGI
              protocol.



       ----ssttaarrtt--aapppp--sseerrvveerr==llooccaallhhoosstt::PPOORRTT,,NNUUMM==PPAATTHH,,MMAASSKK
              Causes the userver to start one or more application  servers  on
              the userver's localhost.  The NUM parameter specifies the number
              of copies of the application server that will be started. If NUM
              is  greater than 1, then the application server copies will lis-
              ten on consecutive ports starting with PORT. The PATH  parameter
              gives an absolute path to the application server executable. The
              MASK parameter is optional, and specifies the CPU affinity  mask
              that  will apply to the newly started application servers.  Here
              is an example:


              ----ssttaarrtt--aapppp--sseerrvveerr==llooccaallhhoosstt::99000000,,
              1188==//uussrr//ssppeecc//ssppeeccwweebb9999--ffccggii..ppll,, 00xx000000dd


              In  this  example,  18 copies of the /usr/spec/specweb99-fcgi.pl
              script will be started.  These application servers  will  listen
              on  ports  9000  - 9017 on the userver's localhost.  The MASK of
              0x000d  is  the  CPU  affinity  mask,  as  interpretd   by   the
              sched_setaffinity system call.



       ----ddyynn--bbuuffffeerr--ssiizzee NN
              The  number  of  bytes  to  allocate  at initialization time for
              buffering replies to  dynamic  requests.   The  default  is  one
              megabyte  (1048576  bytes).   The  number of such buffers can be
              specified using ----nnuumm--ddyynn--bbuuffffeerrss  or  ----nnuumm--ddyynn--bbuuffffeerrss--ppeerr--aapppp
              or  ----nnuumm--ddyynn--bbuuffffeerrss--ppeerr--aappppsseerrvveerr  (see  below).   If  none of
              these options is specified, then by default  the  userver  allo-
              cates 2 buffers per application server.


       ----nnuumm--ddyynn--bbuuffffeerrss NN
              The  number  of  buffers  to allocate at initialization time for
              buffering replies to dynamic requests.  If this option is speci-
              fied,  then the ----nnuumm--ddyynn--bbuuffffeerrss--ppeerr--aapppp and ----nnuumm--ddyynn--bbuuffffeerrss--
              ppeerr--aappppsseerrvveerr options are ignored.


       ----nnuumm--ddyynn--bbuuffffeerrss--ppeerr--aapppp NN
              The number of buffers, per application  (see  the  ----aapppp  option
              below), to allocate at initialization time for buffering replies
              to dynamic requests.  If this  option  is  specified,  then  the
              ----nnuumm--ddyynn--bbuuffffeerrss--ppeerr--aappppsseerrvveerr  option is ignored.  This option
              is ignored if the ----nnuumm--ddyynn--bbuuffffeerrss option is specified.


       ----nnuumm--ddyynn--bbuuffffeerrss--ppeerr--aappppsseerrvveerr NN
              The number of buffers, per application  server  (see  the  ----aapppp
              option  below), to allocate at initialization time for buffering
              replies to dynamic requests.  The default is 2.  This option  is
              ignored  if  either  the  ----nnuumm--ddyynn--bbuuffffeerrss  or  the  ----nnuumm--ddyynn--
              bbuuffffeerrss--ppeerr--aapppp option is specified.


       ----ddyynn--lloocckk--ppaaggeess
              Lock all dynamic buffer pages into memory (must run as root  for
              this to work).


       ----ddyynn--ttoouucchh--ppaaggeess
              Touch  each  dynamic  buffer  page at initialization time.  This
              should have the effect of faulting them into  memory.   However,
              in  the  absense of the ----ddyynn--lloocckk--ppaaggeess option, these pages are
              still subject to being paged out.


OOPPTTIIOONNSS ((FFOORR UUSSEE WWIITTHH SSIIGGIIOO))


       --aa

       ----ssiiggiioo--aacccceeppttss
              Use asynchronous notification via SIGIO to  accept  new  connec-
              tions.   Asynchronous notification may sound costly at first but
              consider that some form of asynchronous notification may be  the
              only  way  for an application that is in the middle of something
              (e.g., computation) to find out about a connection requests.


       --kk

       ----ssiiggiioo--uussee--pprrooccmmaasskk
              To disable and later enable asynchronous notification of  incom-
              ing  requests  when  using SIGIO one can use ffccnnttll(()) to turn off
              and on asynchronous notification or use ssiiggpprrooccmmaasskk(())..  Be care-
              ful  of race conditions.  By default the server uses ffccnnttll(()) but
              this option says to use ssiiggpprrooccmmaasskk(()) instead.


OOPPTTIIOONNSS ((FFOORR AASSYYNNCCHHRROONNOOUUSS II//OO))

       This is experimental and currently the userver only makes use of  asyn-
       chronous  socket  I/O.   This  is  still under development and is being
       tested.  See aio_layer.h for a definition of  the  interface  that  the
       userver  uses to interact with the underlying asynchronous layer.  Note
       that not all of the calls in aio_layer.h are meant to be  asynchronous.
       Some  are  simply  required  in  order  to  complete  the layer.  E.g.,
       aio_sock_create is synchronous but it is used to create a  socket  that
       can be used asynchronously.


       ----uussee--aaiioo--aacccceepptt

       ----uussee--aaiioo--rreeaadd

       ----uussee--aaiioo--wwrriittee

       ----uussee--aaiioo--cclloossee
              Use  the  asynchronous version of the corresponding system calls
              for socket I/O.  These definitions exist but are  all  currently
              only  used  together.   It's  pretty  unlikely that any of these
              could be used independently.


       ----uussee--ssoocckkeett--aaiioo
              Use ansynchronous I/O for sockets.  This turns  on  all  of  the
              above options.


       ----uussee--aaiioo--wwaaiitt
              There  are  two  ways  to  get  events  from the AIO layer.  The
              aio_wait call returns available events of all types in a  single
              array.  It's  then up to the userver to handle them in the order
              they appear or to sort through them.  This is not on by  default
              and   by   default   the   userver   uses   multiple   calls  to
              aio_sock_getevents which only gets events events of a  specified
              type.   Using aio_sock_getevents permits us to get all events of
              a specified type and to process them. This enables us  to  order
              events to be processed by event type.


       ----aaiioo--aacccceepptt--tthhoolldd=NN
              This  is  meant  to  control  the  maximum number of outstanding
              accept calls that can be initiated (preposted).  Using  this  in
              conjunction with --accept-count (-m) we should be able to impact
              the accept rate.  I think that larger  values  of  --aio-accept-
              thold used in conjunction with --accept-count 0 (-m 0) should be
              pretty aggressive about accepting new connections.  This  hasn't
              been  tested  very  extensively.  Especially in conjunction with
              different values of --accept-count.


       ----aaiioo--rreeaadd--bbeeffoorree--aacccceepptt
              With this option the userver calls aio_sock_read_accept whenever
              a new connection should be accepted.  This initiates a read call
              before initiating an accept call.  This informs  the  underlying
              system  of where the read buffer is located so that when data is
              available it  can  be  immediately  placed  into  the  specified
              buffer.


       ----aaiioo--rreeaadd--bbeeffoorree--wwrriittee
              With  this  option  the  userver initiates a read call before it
              tries to write  a  request.   Again  this  is  meant  to  permit
              arriving  data  to  be  copied  directly into the specified read
              buffer.  It can only be initiated after  the  request  has  been
              parsed  and is deemed to be complete.  Otherwise a prepost might
              possibly allow the read buffer to be overwritten.


       ----aaiioo--aacccceepptt--eevveennttss--lliimmiitt=NN
              Limits how many accept completion  events  to  get  out  of  the
              accept  completion queue at one time.  The idea is that it might
              be possible to use this and the read and write limits  below  in
              order to control how the work being processed is balanced.  Note
              that one might actually prefer to adjust  these  values  dynami-
              cally.


       ----aaiioo--wwrriittee--eevveennttss--lliimmiitt=NN
              Limits  how many write completion events to get out of the write
              completion queue at one time.


       ----aaiioo--rreeaadd--eevveennttss--lliimmiitt=NN
              Limits how many read completion events to get out  of  the  read
              completion queue at one time.


       ----aaiioo--ccoommpplleettiioonn--oorrddeerr=ssttrriinngg
              Set  the  order  in  which completion events will get processed.
              The string must contain 'r', 'w', and 'a' characters.  Read com-
              pletions are specified with 'r', write completions with 'w', and
              accept completions with 'a'.  So "rwa" means process  read  com-
              pletions,  then,  write  completions  followed by accept comple-
              tions.  Note that it is  possible  to  specify  a  string  like:
              "rwrwa".


       ----aaiioo--ccoommppllqq--ccoouunntt=[[11||33]]
              Specifies how many completion queus to use.  Currently only sup-
              ports 1 or 3.  Note that for a single completion  queues  limits
              specified  on --aio-write-events-limit, --aio-read-events-limit,
              or --aio-accept-events-limit don't really  apply.   Instead  the
              sum  of  these  is used to limit the number of events handled at
              one time (in the 1 queue case).


OOPPTTIIOONNSS ((FFOORR OOPPEENN FFIILLEE AANNDD HHEEAADDEERR CCAACCHHIINNGG))


       --CC

       ----ccaacchhiinngg--oonn
              Turns caching on.


       ----ccaacchhee--ttaabbllee--ssiizzee==_N
              Specifies the size of the hash table used to cached files.   One
              entry  is  used per cached file.  NOTE: if the ----ccaacchhee--mmaaxx--llooaadd--
              ffaaccttoorr is exceeded the server will print a message and exit.  We
              do not automatically increase the size of the hash table because
              we want to ensure identical and repeatable  behaviour  from  one
              experiment to the next.


       ----ccaacchhee--mmaaxx--llooaadd--ffaaccttoorr==_N
              Specifies  the  maximum proportion of entries that can be filled
              in the hash table, expressed as a fraction of  the  table  size.
              For  example  ----ccaacchhee--mmaaxx--llooaadd--ffaaccttoorr == 00..7700 will not permit the
              hash table to become greater than 70% full.  If it does, a  mes-
              sage is printed and the server exits.


       ----ccaacchhee--mmaaxx--bbyytteess==_N
              Specifies the maximum number of bytes cached.


       ----ccaacchhee--mmaaxx--ffiillee--ssiizzee==_N
              Don't cache files larger than _N bytes.


       ----ccaacchhee--ttaabbllee--pprriinntt
              When  the program ends, print out the contents of the hash table
              used for caching.


       ----ccaacchhee--ffoorr--ssppeecc
              This enables a special hash function that does  perfect  hashing
              on URLs requested by SPECweb99.  This is intended for experimen-
              tation only.


       ----ccaacchhee--lloocckk--ppaaggeess
              Lock all cached pages into memory (must run as root for this  to
              work).


       ----ccaacchhee--wwaarrmm_<_f_i_l_e_n_a_m_e_>
              If  specified  and  caching is enabled then read a list of files
              and/or directories in <filename>.  For each file add it  to  the
              userver  cache  and touch each page.  If it's a directory, cache
              and touch each file in the directory.  If --cache-table-print is
              declared then print the cache after it's been primed.


OOPPTTIIOONNSS ((FFOORR DDEEBBUUGGGGIINNGG))


       --DD [[00xx]]NN

       ----ddeebbuugg--mmaasskk==_[_0_x_]_N]]
              Specify  a  debug  mask.  If prefixed with '0x', the argument is
              interpreted as hexadecimal; otherwise it is interpreted as deci-
              mal.    For   maximum   debugging   detail  use  ----ddeebbuugg--mmaasskk  ==
              _0_x_f_f_f_f_f_f_f_f_.  To turn debugging messages off use  ----ddeebbuugg--mmaasskk  ==
              _0_x_0_.   See  debug.h  for details.  Note: that to compile without
              debugging also see debug.h.


       ----ttrraaccee--ssuummmmaarryy
              Keep track of information regarding system  calls  and  print  a
              summary.   If  tracing  is  enabled  a  list of each event being
              traced will be dumped to a trace output file.


       ----ttrraaccee--ssuummmmaarryy--oonnllyy
              Keep track of information regarding system  calls  and  print  a
              summary.   If  this  option is enabled individual events are not
              actually recorded but instead information to produce  a  summary
              of each event type is tracked. For example, minimum, maximum and
              average call times for each system call being traced.


       ----ttrraaccee--ffiilleennaammee ppaatthh
              Specify the name of the file to write tracing  output  to,  when
              tracing is enabled.


       --ii

       ----iinntteerraaccttiivvee
              Turns  on  interactive  mode.  The server stops between calls to
              process events and prompts the user for input.  This permits the
              user to query some of the state of the server or to step through
              server execution.  At the prompt type 'h' or '?' for a  list  of
              commands.


       --PP

       ----ccoouunntt--ssiiggppiippeess
              Install  a  signal handler that simply counts the number of SIG-
              PIPE signals received.


OOPPTTIIOONNSS ((FFOORR EEXXPPEERRIIMMEENNTTSS RREELLAATTEEDD TTOO BBOOUUNNDDIINNGG PPEERRFFOORRMMAANNCCEE))

       These options are designed to have the server stop processing a request
       at various stages of a requests life.  It stops handling the request by
       closing it's end of the socket and not working on that request anymore.
       I've  attempted to list these in the order of earliest time to drop the
       request to latest.  The idea is that by running a series of experiments
       by  using each of these options one might be able to get a sense of how
       much additional stage costs.


       --nn

       ----nnoo--aacccceeppttss

       ----lliisstteenn--oonnllyy
              This puts the server into a mode where it only ever  listens  to
              requests.   It  never makes any attempt to process requests.  So
              it never even accepts any requests.  The believe  is  that  this
              might  be  used  to provide insights into the amount of overhead
              incurred when kernel  TCP  SYN  queues  and  application  listen
              queues become full.


       --AA

       ----aacccceeppttss--oonnllyy

       ----cclloossee--aafftteerr--aacccceepptt
              In  this  mode the server accepts and closes incoming connection
              requests as quickly as possible.  At  the  time  this  was  done
              _c_l_o_s_e_(_)  would  block  until  the call completed (despite the fd
              being in non blocking mode).  So  immediately  after  accepting,
              call _c_l_o_s_e_(_)_.  to terminate the connection.


       ----cclloossee--aafftteerr--ssoocckk--iinniitt
              The server accepts a connection, initializes the socket (setting
              socket options like socket buffer sizes, non blocking mode, etc)
              and then it closes the connection.


       ----cclloossee--aafftteerr--rreeaadd
              The  server  accepts  a connection, initializes the socket reads
              the request and then closes the connection.


       ----cclloossee--aafftteerr--ppaarrssee
              The server accepts a connection, initializes  the  socket  reads
              the request, parses the requests and then closes the connection.


OOPPTTIIOONNSS ((FFOORR UUSSEE WWIITTHH TTHHEE SSEENNDD EENNHHAANNCCEEDD KKEERRNNEELL))

       WARNING: these options are highly experimental and subject to  continu-
       ous change.

       These options specify how the uusseerrvveerr interacts with new Linux Scalable
       Event  Notification  and  Delivery  (SEND)  kernel   mechanisms.    See
       [Ostrowski-2000] for more details on SEND.


       --KK [[00xx]]NN

       ----kkddeebbuugg--mmaasskk==_[_0_x_]_N]]
              Specify  a  debugging  mask which is passed to the _e_v_t_c_t_l system
              call to set a kernel debugging mask for the SEND  related  parts
              of  the  kernel.   If prefixed with '0x', the argument is inter-
              preted as hexadecimal; otherwise it is interpreted as decimal.


       ----sseenndd--ppoollllss--ffoorr--aacccceeppttss
              The send loop polls for new connections.


       --BB

       ----bblloocckk--ffoorr--sseenndd__eevveennttss
              When there are not more events to process, block  and  wait  for
              one or more new events by calling _e_v_t_c_t_l_(_)_.


       --EE

       ----sseenndd--eevveennttss
              Use send events. This version does not do notification.


       --GG

       ----uussee--ggeettppiidd
              If  we aren't blocking to wait for events (by calling evtctl) we
              may wish to make a system call to give the kernel  a  chance  to
              deliver events to the application (since they are delivered when
              returning from a syscall.  In this case we use _g_e_t_p_i_d_(_)  because
              it is likely fast.


       --YY

       ----sseenndd--iioo--eevveennttss
              Use send events. This version does do notification.


       --NN

       ----sseenndd--lloooopp
              Use  the send loop.  Can potentially get and process send events
              even while using select.  This bypasses the use  of  the  select
              call.


       --bb NN

       ----eeccbb--bbuuff--eennttrriieess==_N
              How many events can be stored in the application's event control
              buffer (ecb).


       --QQ NN

       ----eeccbb--hhii--wwaatteerr==_N
              Set the high water mark used for the event control buffer (ecb).
              One of the things we've tried is to turn event delivery off when
              the _-_-_e_c_b_-_h_i_-_w_a_t_e_r mark is reached and  then  to  turn  delivery
              back on when the _-_-_e_c_b_-_l_o_w_-_w_a_t_e_r mark is reached.


       --qq NN

       ----eeccbb--llooww--wwaatteerr==_N
              Set  the low water mark used for the event control buffer (ecb).
              One of the things we've tried is to turn event delivery off when
              the  _-_-_e_c_b_-_h_i_-_w_a_t_e_r  mark  is  reached and then to turn delivery
              back on when the _-_-_e_c_b_-_l_o_w_-_w_a_t_e_r mark is reached.


       --UU

       ----aauuttoo--aacccceepptt
              Turn on the SEND kernel's auto accept mechanisms.  When new con-
              nection  requests  arrive  the kernel automatically accepts them
              (auto accepts 'em) and notifies the application  with  an  event
              containing the new connection's fd.


       ----aauuttoo--aacccceepptt--aappeerrttuurree
              Control  the  difference  between  the number of connections the
              kernel has autoaccepted and the number of connections the appli-
              cation has closed.  Without this type of control the autoaccept-
              ing can get out of control and the kernel  can  spend  too  much
              time  auto  accepting new connections and the application is not
              able to make much forward progress on existing connections.


       ----uussee--aacccceepptt--sseenndd
              Use a special version of accept that returns  event  information
              related to the accepted connection/socket.


       --jj

       ----kkeerrnneell--iinnffoo
              Experimental: was to tell the application that the kernel has an
              interface available for obtaining  more  information  about  the
              size  and  number of entries in some of the kernel queues (e.g.,
              the TCP SYNQs and the application's listenq).

OOPPTTIIOONNSS ((FFOORR CCHHOOOOSSIINNGG AANNDD CCOONNTTRROOLLLLIINNGG AA VVIICCTTIIMM))

       WARNING: These are just some hacks to try out some ideas.

       --FF

       ----vviiccttiimm ssttrriinngg
              Set the specified string as a victim string.  Any uri that  con-
              tains  this  string  is  declared a victim. How it is victimized
              depends on the value used in the --victim-skip option.   If  the
              --victim-skip option is not set there is no affect on the speci-
              fied victim file.


       ----vviiccttiimm--sskkiipp NN
              If N is > 0, then writes to the client socket  will  be  skipped
              N-1  times.  The idea is to slow down the response to any client
              that requests the specified victim file.  Specifically, when the
              event  mechanism  indicates that the socket is ready for writing
              the write will just be skipped.  Note that this  probably  won't
              work  with  epoll  if  you are using edge triggered events. Also
              note that the amount of slow down depends on the number of other
              sockets  that are ready for processing when the event mechanisim
              returns and the amount of processing required for each of  those
              events.

              If N = -1 then no writes are skipped but instead the server uses
              madvise after it has written the bytes to advise  the  operating
              system that it doesn't need the bytes for this file anymore.


       ----ccaacchhee--mmiissss--sskkiipp NN
              This  is  specific to BSD (possibly FreeBSD).  If N is > 0, then
              sendfile calls that would block because of  disk  I/O  (i.e.,  a
              file  cache  miss) will be skipped N times.  The idea is to slow
              down the response to any client that requests a file that  might
              require  disk  I/O.   In  theory  this  may  permit us to favour
              requests for files that are in the  file  cache.   Specifically,
              when  the event mechanism indicates that the socket is ready for
              writing  the  sendfile  call  will  be  made   with   the   flag
              SF_NODISKIO.

              Currently  this  isn't  intended  to be used in conjunction with
              --victim and --victim-skip (i.e., I haven't thought through  the
              behaviour).


OOUUTTPPUUTT
       This  section describes portions of the output produced during the exe-
       cution of the uusseerrvveerr..


       The first portion of output lists the program name and the command line
       parameters.   The  second  portion  of  output lists the setting of all
       options.  This is the most reliable way to find out  the  default  set-
       tings for some options.


       The next two sections identify operating system and per user or process
       limits.

       The remainder of the output provides  more  information  about  default
       settings  of  various parameters and a large number of statistics about
       the execution of the server.


AAUUTTHHOORRSS
       uusseerrvveerr was developed by Tim Brecht by starting  with  some  micro  web
       servers  originally  developed  by Abhishek Chandra and David Mosberger
       [Chandra-2001].  David Pariag contributed the current  caching  engine.
       One of the hash functions is from Bob Jenkin's web site.


BBUUGGSS
       Probably many.

       NOTE: very few if any checks are performed to see if the combination of
       options being used makes sense.  For example, the behaviour from  using
       both the ----sseelleecctt--lloooopp and ----sseenndd--lloooopp options is undefined.

       Always be sure to double-check results and don't fall prey to measuring
       client-performance instead of server performance!  The tool hhttttppeerrff  is
       very good at generating loads.

       Many  of  the single letter options are difficult to relate to anything
       meaningful. As the number of options grew I eventually started  to  run
       out of alphabet and added long options.

       The  user-interface  definitely could be improved.  A simple configura-
       tion file might be more suitable than the many command-line options.


RREEFFEERREENNCCEESS
       [Shukla-2006]    Amol Shukla and Tim Brecht, TCP Connection  Management
                        Mechanisms  for Improving Internet Server Performance,
                        First IEEE Workshop on Web  Systems  and  Technologies
                        (HotWeb 2006), Boston, MA, November, 2006.


       [Brecht-2006]    Tim  Brecht, G. (John) Janakiraman, Brian Lynn, Vikram
                        Saletore, Yoshio Turner, Evaluating Network Processing
                        Efficiency   with  Processor  Partitioning  and  Asyn-
                        chronous I/O, Proceedings  of  EuroSys  2006,  Leuven,
                        Belgium, April 2006.


       [Gammo-2004]     Louay  Gammo,  Tim  Brecht,  Amol  Shukla,  and  David
                        Pariag, Comparing and Evaluating  epoll,  select,  and
                        poll  Event  Mechanisms, Ottawa Linux Symposium, July,
                        2004.


       [Brecht-2004]    Tim   Brecht,   Louay   Gammo,   and   David   Pariag,
                        accept()able  Strategies for Improving Web Server Per-
                        formance, 2004  USENIX  Annual  Technical  Conference:
                        General Track, Boston, June, 2004.


       [Brecht-2001]    Tim Brecht and Michal Ostrowski, Exploring the Perfor-
                        mance of Select-based Internet Servers, HP Labs  Tech-
                        nical Report HPL-2001-314, November, 2001.


       [Chandra-2001]   A.  Chandra  and  D.  Mosberger,  Scalability of Linux
                        Event-Dispatch Mechanisms,  Proceedings  of  the  2001
                        USENIX Annual Technical Conference, June 2001.


       [Ostrowski-2000] Michal Ostrowski, A Mechanism for Scalable Event Noti-
                        fication and Delivery in Linux, M.Math Thesis, Depart-
                        ment  of  Computer  Science,  University  of Waterloo,
                        November, 2000.



userver-0.6.1                     1 Aug 2010                        userver(1)
