Contributions to the Linux Kernel

Martin Karsten

IRQ Suspension

I have worked towards a kernel modification that adds an IRQ suspension mechanism to the Linux kernel, based on the idea in our Sigmetrics 2024 paper. I have made various small contributions during this work:

net/mlx4: Track RX allocation failures in a stat (Tested-by)
net/mlx4: link NAPI instances to queues and IRQs (Tested-by)
net/mlx4: support per-queue statistics via netlink (Tested-by)
eventpoll: Annotate data-race of busy_poll_usecs (Author)
net: napi: Add napi_config (Co-developed-by)

The resulting patch series has been accepted for the Linux kernel:

eventpoll: Control irq suspension for prefer_busy_poll (Author)
eventpoll: Trigger napi_busy_loop, if prefer_busy_poll is set (Author)
net: Add control functions for irq suspension (Author)
net: Add napi_struct parameter irq_suspend_timeout (Author)
selftests: net: Add busy_poll_test (Co-developed-by)
docs: networking: Describe irq suspension (Co-developed-by)

Complete patch

Submission history with cover letters:

Joe Damato has given related presentations to the Linux Networking community:

NetDev 0x19: IRQ Suspension: a new, efficient mechanism for packet delivery.
NetDev 0x18: Real world tips, tricks, and notes of using epoll-based busy polling to reduce latency.

The overall research & development story has received a fair bit of media coverage:

last updated Mar 13, 2025 - Martin Karsten