On Sun, May 23, 2021 at 8:58 AM Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx> wrote: > > On Sun, May 23, 2021 at 4:48 AM Toke Høiland-Jørgensen <toke@xxxxxxxxxx> wrote: > > > > Still wrapping my head around this, but one thing immediately sprang to > > mind: > > > > > + * long bpf_timer_mod(struct bpf_timer *timer, u64 msecs) > > > + * Description > > > + * Set the timer expiration N msecs from the current time. > > > + * Return > > > + * zero > > > > Could we make this use nanoseconds (and wire it up to hrtimers) instead? > > I would like to eventually be able to use this for pacing out network > > packets, and msec precision is way too coarse for that... > > msecs are used to avoid exposing jiffies to bpf prog, since msec_to_jiffies > isn't trivial to do in the bpf prog unlike the kernel. > hrtimer would be great to support as well. > It could be implemented via flags (which are currently zero only) > but probably not as a full replacement for jiffies based timers. > Like array vs hash. bpf_timer can support both. After reading the hrtimer code I might take the above statement back... hrtimer looks strictly better than timerwheel and jiffies. It scales well and there are no concerns with overload, since sys_nanonsleep and tcp are heavy users. So I'm thinking to drop jiffies approach and do hrtimer only. wdyt?
