On Sat, Oct 14, 2017 at 12:26:28AM +0000, Eric Dumazet wrote: > On Fri, Oct 13, 2017 at 5:09 PM, Martin KaFai Lau <ka...@fb.com> wrote: > > On Fri, Oct 13, 2017 at 10:08:07PM +0000, Wei Wang wrote: > >> From: Wei Wang <wei...@google.com> > >> > >> In order to not dirty the cacheline too often, we try to only update > >> dst->__use and dst->lastusetime at most once per jiffy. > > > > > >> As dst->lastusetime is only used by ipv6 garbage collector, it should > >> be good enough time resolution. > > Make sense. > > > >> And __use is only used in ipv6_route_seq_show() to show how many times a > >> dst has been used. And as __use is not atomic_t right now, it does not > >> show the precise number of usage times anyway. So we think it should be > >> OK to only update it at most once per jiffy. > > If __use is only bumped HZ number of times per second and we can do ~3Mpps > > now, > > would __use be way off? > > It is not used in the kernel, and is not even reported by user space > (iproute2) currently. > > With the percpu stuff, we never did the sum anyway. The pcpu_rt currently does not track __use.
> > I believe we should be fine by being very lazy on this field. > > If really someones complain, we will see, but insuring ~one update per > HZ seems fine. Fair point. Make sense. We currently also don't find the ipv6_route proc-file very useful other than debugging purpose.
