From: Peter Zijlstra <peterz@infradead.org>
To: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Cc: linux-kernel@vger.kernel.org,
Fernando Luis Vazquez Cao <fernando_b1@lab.ntt.co.jp>,
Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
Frederic Weisbecker <fweisbec@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Arjan van de Ven <arjan@linux.intel.com>,
Oleg Nesterov <oleg@redhat.com>,
Preeti U Murthy <preeti@linux.vnet.ibm.com>,
Denys Vlasenko <vda.linux@googlemail.com>,
stable@vger.kernel.org
Subject: Re: [PATCH 2/2] nohz: use delayed iowait accounting to avoid race on idle time stats
Date: Fri, 18 Apr 2014 10:44:01 +0200 [thread overview]
Message-ID: <20140418084401.GC11096@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <5350BD85.4050302@jp.fujitsu.com>
On Fri, Apr 18, 2014 at 02:52:05PM +0900, Hidetoshi Seto wrote:
> I think it also works... but I have some concerns here:
>
> - it changes golden path in scheduler core.
> impact for performance is questionable.
We should be able to measure that, but like said, it shouldn't change
the number of atomic ops and makes sure its all in the same cacheline,
so the additional code is all cheap.
> - it forces managing last_iowait even if system is in busy
> I guess it will drop max performance of the system
> while my proposed fix only touches procedure for idle
> with nohz.
That could be fixed by looking to see if the remote rq is idle.
> By the way, I have posted my v4 patch set:
> https://lkml.org/lkml/2014/4/17/120
>
> I'll happy if you could give your comments on it too!
Yeah, I saw that, didn't have time yet, will hopefully get to it soon
:-)
next prev parent reply other threads:[~2014-04-18 8:44 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-10 9:07 [PATCH v3 0/2] nohz: fix idle accounting in NO_HZ kernels Hidetoshi Seto
2014-04-10 9:11 ` [PATCH 1/2] nohz: stop updating sleep stats from get_cpu_{idle,iowait}_time_us() Hidetoshi Seto
2014-04-15 8:48 ` Peter Zijlstra
2014-04-15 8:49 ` Peter Zijlstra
2014-04-10 9:13 ` [PATCH 2/2] nohz: use delayed iowait accounting to avoid race on idle time stats Hidetoshi Seto
2014-04-15 10:04 ` Peter Zijlstra
2014-04-16 6:30 ` Hidetoshi Seto
2014-04-15 10:19 ` Peter Zijlstra
2014-04-16 6:33 ` Hidetoshi Seto
2014-04-16 9:36 ` Peter Zijlstra
2014-04-17 0:42 ` Hidetoshi Seto
2014-04-17 10:05 ` Peter Zijlstra
2014-04-17 10:09 ` Peter Zijlstra
2014-04-18 5:52 ` Hidetoshi Seto
2014-04-18 8:44 ` Peter Zijlstra [this message]
2014-04-15 3:11 ` [PATCH v3 0/2] nohz: fix idle accounting in NO_HZ kernels Hidetoshi Seto
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