From: Peter Zijlstra <peterz@infradead.org>
To: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: "mingo@elte.hu" <mingo@elte.hu>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"chris@frostnet.net" <chris@frostnet.net>,
"debian00@aliceadsl.fr" <debian00@aliceadsl.fr>,
"hpa@zytor.com" <hpa@zytor.com>,
"jonathan.protzenko@gmail.com" <jonathan.protzenko@gmail.com>,
"mans@mansr.com" <mans@mansr.com>,
"psastudio@mail.ru" <psastudio@mail.ru>,
"rjw@sisk.pl" <rjw@sisk.pl>,
"stephan.eicher@web.de" <stephan.eicher@web.de>,
"sxxe@gmx.de" <sxxe@gmx.de>,
"thomas@archlinux.org" <thomas@archlinux.org>,
"venki@google.com" <venki@google.com>,
"wonghow@gmail.com" <wonghow@gmail.com>,
"stable@kernel.org" <stable@kernel.org>,
tglx <tglx@linutronix.de>
Subject: Re: [patch 1/3] sched: init rt_avg stat whenever rq comes online
Date: Tue, 17 Aug 2010 10:51:25 +0200 [thread overview]
Message-ID: <1282035085.1926.2164.camel@laptop> (raw)
In-Reply-To: <1281986708.1926.1877.camel@laptop>
On Mon, 2010-08-16 at 21:25 +0200, Peter Zijlstra wrote:
> You can use something like:
>
> suspend:
> __get_cpu_var(cyc2ns_suspend) = sched_clock();
>
> resume:
> for_each_possible_cpu(i)
> per_cpu(cyc2ns_offset, i) += per_cpu(cyc2ns_suspend);
>
> or something like that to keep sched_clock() stable, which is exactly
> what most (all?) its users expect when we report the TSC is usable.
That's actually broken, you only want a single offset, otherwise we
de-sync the TSC, which is bad.
So simply store the sched_clock() value at suspend time on the single
CPU that is still running, then on resume make sure sched_clock()
continues there by adding that stamp to all CPU offsets.
next prev parent reply other threads:[~2010-08-17 8:51 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-13 19:45 [patch 0/3] sched: fixes related to scaling down cpu power with RT tasks Suresh Siddha
2010-08-13 19:45 ` [patch 1/3] sched: init rt_avg stat whenever rq comes online Suresh Siddha
2010-08-16 7:47 ` Peter Zijlstra
2010-08-16 17:36 ` Suresh Siddha
2010-08-16 19:25 ` Peter Zijlstra
2010-08-17 8:51 ` Peter Zijlstra [this message]
2010-08-19 0:20 ` Suresh Siddha
2010-08-19 8:53 ` Peter Zijlstra
2010-08-20 0:03 ` Suresh Siddha
2010-08-20 8:54 ` Peter Zijlstra
2010-08-20 14:16 ` [tip:sched/urgent] x86, tsc, sched: Recompute cyc2ns_offset's during resume from sleep states tip-bot for Suresh Siddha
2010-08-13 19:45 ` [patch 2/3] sched: fix minimum power returned by update_cpu_power() Suresh Siddha
2010-08-16 7:50 ` Peter Zijlstra
2010-08-16 17:37 ` Suresh Siddha
2010-08-13 19:45 ` [patch 3/3] sched: move sched_avg_update() to update_cpu_load() Suresh Siddha
2010-08-16 8:00 ` Peter Zijlstra
2010-08-16 17:46 ` Suresh Siddha
2010-08-16 19:31 ` Peter Zijlstra
2010-08-20 0:51 ` Suresh Siddha
2010-08-20 9:25 ` Peter Zijlstra
2010-08-20 13:47 ` Peter Zijlstra
2010-08-23 20:42 ` Suresh Siddha
2010-09-09 19:45 ` [tip:sched/urgent] sched: Move " tip-bot for Suresh Siddha
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