Re: [PATCH] rcu: restore correct batch limiting
From: Eric Dumazet
Date: Thu Oct 18 2012 - 12:10:24 EST
On Thu, 2012-10-18 at 08:25 -0700, Paul E. McKenney wrote:
> On Thu, Oct 18, 2012 at 02:44:50PM +0200, Eric Dumazet wrote:
> > Having 2 billions callbacks on one cpu would be problematic, I really
> > hope nobody relies on this ;)
> Fair point! ;-)
> But just making everything long makes it quite easy to analyze.
> > I guess the 10/infinity switch should be smarter.
> > something like the following maybe :
> > rdp->blimit = max(blimit, rdp->qlen >> 6);
> > (if queue is big, dont wait to hit 10000 before allowing more items to
> > be handled per round)
> The -rt guys would not be amused. :-(
> But for non-realtime use, increasing rcutree.blimit either at boot or
> via sysfs could make sense. It is also likely that I will move callback
> processing to a kthread at some point, which would allow some additional
Ah, I now realize the loop can exceed blimit, but is it true for BH
variant ? (Not really a problem for 3.6/3.7 kernels, but prior ones)
if (++count >= bl &&
(!is_idle_task(current) && !rcu_is_callbacks_kthread())))
I wonder if ksoftirqd should be included as well...
> Furthermore, it would be easy to have one default for non-rt and another
> for -rt, if that would help.
> > Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
> > Please dont forget stable teams. (3.2 + )
> Added both, please see below!
Seems fine to me, thanks Paul !
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