On Tue, May 21, 2024 at 2:59 PM Barret Rhoden <brho@xxxxxxxxxx> wrote: > > hi - > > we've noticed some variability in bpf timer expiration that goes away if > we change the timers to run in hardirq context. What kind of variability are we talking about? > i imagine the use of softirqs was to keep the potentially long-running > timer callback out of hardirq, but is there anything particularly > dangerous about making them run in hardirq? exactly what you said. We don't have a good mechanism to keep bpf prog runtime tiny enough for hardirq. > would you all be open to a patch that makes that a flag or something? > e.g. BPF_F_TIMER_HARDIRQ. There are very few users of MODE_*_HARD in the kernel. Even the most demanding users like networking are using soft. Have you tried BPF_F_TIMER_CPU_PIN to reduce jitter?
