From: Mike Galbraith <umgwanakikbuti@gmail.com>
To: Christoph Lameter <cl@linux.com>
Cc: Michal Hocko <mhocko@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: fast path cycle muncher (vmstat: make vmstat_updater deferrable again and shut down on idle)
Date: Wed, 27 Jan 2016 04:12:27 +0100 [thread overview]
Message-ID: <1453864347.3622.10.camel@gmail.com> (raw)
In-Reply-To: <alpine.DEB.2.20.1601261317410.4024@east.gentwo.org>
Good morning,
On Tue, 2016-01-26 at 13:20 -0600, Christoph Lameter wrote:
> On Tue, 26 Jan 2016, Mike Galbraith wrote:
>
> > > The system going idle is a fastpath. Mind boogling.
> >
> > Hohum, noted. Now what about those cycles, and the sleeping lock you
> > injected for -rt?
>
> Since we (the NOHZ people) care mostly about NOHZ then lets restrict
> that to the NOHZ mode. Then it should not affect your load.
Tons of folks do have NO_HZ enabled (including me). Isn't there a spot
somewhere in NO_HZ_FULL code where it can take up residence? (one with
a tad lower maximum call frequency would be good, a nohz_full cpu isn't
necessarily being used for pure compute exclusively)
> Subject: Move quiet_vmstat() to NOHZ code
>
> quiet_vmstat() seems to cause regressions for some load because
> the cpu going idle is a "fastpath". Mind boogling. Strange claim.
> If the system goes idle then it has nothing to do after all
>
> But anyways if we shift the quiet_vmstat() into the NOHZ logic
> when it stops the tick then it will only affect those cores that
> are setup for NOHZ mode. That is where we want this processing
> after all to ensure that the OS keeps itself off those cores.
>
> Signed-off-by: Christoph Lameter <cl@linux.com>
>
>
> Index: linux/kernel/sched/idle.c
> ===================================================================
> --- linux.orig/kernel/sched/idle.c
> +++ linux/kernel/sched/idle.c
> @@ -213,7 +213,6 @@ static void cpu_idle_loop(void)
> */
>
> __current_set_polling();
> - quiet_vmstat();
> tick_nohz_idle_enter();
>
> while (!need_resched()) {
> Index: linux/kernel/time/tick-sched.c
> ===================================================================
> --- linux.orig/kernel/time/tick-sched.c
> +++ linux/kernel/time/tick-sched.c
> @@ -811,6 +811,7 @@ static void __tick_nohz_idle_enter(struc
> ts->idle_calls++;
>
> expires = tick_nohz_stop_sched_tick(ts, now, cpu);
> + quiet_vmstat();
> if (expires.tv64 > 0LL) {
> ts->idle_sleeps++;
> ts->idle_expires = expires;
next prev parent reply other threads:[~2016-01-27 3:12 UTC|newest]
Thread overview: 77+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-19 0:33 mm, vmstat: kernel BUG at mm/vmstat.c:1408! Sasha Levin
2015-12-21 13:08 ` Christoph Lameter
2015-12-21 20:28 ` Sasha Levin
2015-12-21 21:07 ` Sasha Levin
2015-12-21 21:14 ` Christoph Lameter
2015-12-22 17:21 ` Christoph Lameter
2015-12-24 20:14 ` Sasha Levin
2015-12-29 17:01 ` Christoph Lameter
2015-12-29 17:18 ` Christoph Lameter
2016-01-04 18:05 ` Christoph Lameter
2016-01-04 18:46 ` Sasha Levin
2016-01-12 11:31 ` Shiraz Hashim
2016-01-12 12:23 ` Christoph Lameter
2016-01-12 12:27 ` Shiraz Hashim
2016-01-13 11:36 ` Shiraz Hashim
2016-01-13 12:32 ` Shiraz Hashim
2016-01-14 21:06 ` Sasha Levin
2016-01-20 14:37 ` Michal Hocko
2016-01-20 14:56 ` Sasha Levin
2016-01-20 15:10 ` Michal Hocko
2016-01-20 15:20 ` Christoph Lameter
2016-01-20 15:49 ` Sasha Levin
2016-01-20 15:55 ` Christoph Lameter
2016-01-20 21:28 ` Michal Hocko
2016-01-20 21:57 ` Christoph Lameter
2016-01-21 8:24 ` Michal Hocko
2016-01-21 15:45 ` Christoph Lameter
2016-01-21 16:51 ` Michal Hocko
2016-01-21 17:38 ` Christoph Lameter
2016-01-22 11:00 ` Shiraz Hashim
2016-01-22 14:04 ` Michal Hocko
2016-01-22 16:07 ` Christoph Lameter
2016-01-22 16:12 ` Michal Hocko
2016-01-22 16:46 ` Christoph Lameter
2016-01-22 17:12 ` Michal Hocko
2016-01-23 16:21 ` fast path cycle muncher (vmstat: make vmstat_updater deferrable again and shut down on idle) Mike Galbraith
2016-01-24 0:33 ` Christoph Lameter
2016-01-24 2:46 ` Mike Galbraith
2016-01-24 3:46 ` Christoph Lameter
2016-01-24 5:36 ` Mike Galbraith
2016-01-25 17:42 ` Michal Hocko
2016-01-25 18:02 ` Christoph Lameter
2016-01-25 20:13 ` Michal Hocko
2016-01-26 16:25 ` Christoph Lameter
2016-01-26 18:31 ` Mike Galbraith
2016-01-26 18:34 ` Christoph Lameter
2016-01-26 18:45 ` Mike Galbraith
2016-01-26 19:20 ` Christoph Lameter
2016-01-27 3:12 ` Mike Galbraith [this message]
2016-01-27 4:15 ` Mike Galbraith
2016-01-27 16:28 ` Christoph Lameter
2016-01-28 15:36 ` Frederic Weisbecker
2016-01-28 16:42 ` Christoph Lameter
2016-01-26 2:14 ` Mike Galbraith
2016-01-26 2:25 ` Mike Galbraith
2016-01-26 16:26 ` Christoph Lameter
2016-01-26 17:39 ` Mike Galbraith
2016-01-26 18:19 ` Christoph Lameter
2016-01-26 16:26 ` Christoph Lameter
2016-01-26 17:08 ` Mike Galbraith
2016-01-26 18:22 ` Christoph Lameter
2016-01-26 19:09 ` Mike Galbraith
2016-01-26 19:22 ` Christoph Lameter
2016-01-27 16:48 ` [PATCH] mm, vmstat: make quiet_vmstat lighter (was: Re: fast path cycle muncher (vmstat: make vmstat_updater deferrable) " Michal Hocko
2016-01-27 17:03 ` Mike Galbraith
2016-01-27 18:26 ` Christoph Lameter
2016-01-28 15:21 ` Michal Hocko
2016-01-28 16:40 ` Christoph Lameter
2016-01-28 16:53 ` Michal Hocko
2016-01-28 17:05 ` Christoph Lameter
2016-01-28 15:31 ` Michal Hocko
2016-01-28 15:37 ` [PATCH] vmstat: make vmstat_update deferrable (was: Re: [PATCH] mm, vmstat: make quiet_vmstat lighter) " Michal Hocko
2016-01-28 16:48 ` Christoph Lameter
2016-01-28 16:42 ` [PATCH] mm, vmstat: make quiet_vmstat lighter (was: Re: fast " Christoph Lameter
2016-01-24 16:57 ` mm, vmstat: kernel BUG at mm/vmstat.c:1408! Linus Torvalds
2016-01-20 15:14 ` Christoph Lameter
2016-01-20 15:20 ` Michal Hocko
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