On Fri, 3 Feb 2017 09:30:37 +0100 Nikolay Aleksandrov <niko...@cumulusnetworks.com> wrote:
> On 03/02/17 03:47, David Miller wrote: > > From: Nikolay Aleksandrov <niko...@cumulusnetworks.com> > > Date: Tue, 31 Jan 2017 16:31:58 +0100 > > > >> @@ -197,7 +197,8 @@ int br_handle_frame_finish(struct net *net, struct > >> sock *sk, struct sk_buff *skb > >> if (dst->is_local) > >> return br_pass_frame_up(skb); > >> > >> - dst->used = jiffies; > >> + if (br->used_enabled) > >> + dst->used = jiffies; > > > > Have you tried: > > > > if (dst->used != jiffies) > > dst->used = jiffies; > > > > If that isn't effective, you can tweak the test to decrease the > > granularity of the value. Basically, if dst->used is within > > 1 HZ of jiffies, don't do the write. > > > > I suspect this might help a lot, and not require a new bridging > > option. > > > > Yes, I actually have a patch titled "used granularity". :-) I've tested with > different > values and it does help but it either needs to be paired with another similar > test for > the "updated" field (since they share a write-heavy cache line) or they need > to be > in separate cache lines to avoid that dst's source port from causing the load > HitM for > all who check the value. > > I'll run some more tests and probably go this way for now. > > Thanks, > Nik > Since used doesn't need HZ granularity, it reports values in clock_t resolution so storing (and doing cmp and set would mean that it would only be 100 HZ
