On the system you are using you would be working with
/usr/include/bits/typesizes.h:#define   __FD_SETSIZE            1024
see instructions below. The kernel can handle about 400000 fds.


Large number of open files
--------------------------

In order to be able to use more than the default number of
open file descriptors you may need to:
	o increase the limit on the total number of open files
		/proc/sys/fs/file-max  (on Linux systems)
	o increase the size of FD_SETSIZE
			- the way I often do this is to figure out which
				include file __FD_SETSIZE is defined in, copy
				that file into an appropriate directory in
				./include, and then modify it so that if you 
				use -DBIGGER_FD_SETSIZE the larger size gets used

		For example on a RH 9.0 distribution I've copied
			/usr/include/bits/typesizes.h into 
		 ./include/i386-linux/bits/typesizes.h

		Then I modify typesizes.h to look something like:

		#ifdef BIGGER_FD_SETSIZE
		#define __FD_SETSIZE            32767
		#else
		#define __FD_SETSIZE            1024
		#endif

		Note that the since I'm moving and testing the userver
		on may different machines the Makefiles are set up
		to use -I ./include/$(HOSTTYPE)

		This way if you redefine the FD_SETSIZE it will get
		used instead of the default original file.