Re: RCU latency regression in 2.6.16-rc1


* Lee Revell <rlrevell@xxxxxxxxxxx> wrote:

> On Tue, 2006-01-24 at 09:01 +0100, Ingo Molnar wrote:
> > * Lee Revell <rlrevell@xxxxxxxxxxx> wrote:
> >
> > > On Tue, 2006-01-24 at 08:56 +0100, Ingo Molnar wrote:
> > > > * Lee Revell <rlrevell@xxxxxxxxxxx> wrote:
> > > >
> > > > > I ported the latency tracer to 2.6.16 and got this 13ms latency within
> > > > > a few hours. This is a regression from 2.6.15.
> > > > >
> > > > > It appears that RCU can invoke ipv4_dst_destroy thousands of times in
> > > > > a single batch.
> > > >
> > > > could you try the PREEMPT_RCU patch below?
> > >
> > > Sure. If it works do you see this making it in 2.6.16? Otherwise we
> > > still would have a regression...
> >
> > nope, that likely wont make v2.6.16, which is frozen already.
> >
>
> How about just lowering maxbatch to 1000?

does that fix the latency for you? I think "maxbatch=1000" should work
as a boot parameter too.

Ingo
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