From: a.p.zijlstra@chello.nl (Peter Zijlstra)
To: linux-arm-kernel@lists.infradead.org
Subject: [BUG] 2.6.37-rc3 massive interactivity regression on ARM
Date: Wed, 08 Dec 2010 13:40:15 +0100 [thread overview]
Message-ID: <1291812015.28378.24.camel@laptop> (raw)
In-Reply-To: <20101205162151.GH9138@n2100.arm.linux.org.uk>
On Sun, 2010-12-05 at 16:21 +0000, Russell King - ARM Linux wrote:
> I'm not sure that's the correct fix - it looks like sched_clock_cpu()
> should already be preventing scheduler clock time going backwards.
>
> Hmm. IOP32x seems to have a 32-bit timer clocked at 200MHz. That means
> it wraps once every 21s. However, we have that converted to ns by an
> unknown multiplier and shift. It seems that those are chosen to
> guarantee that we will cover only 4s without wrapping in the clocksource
> conversion. Maybe that's not sufficient?
>
> Could you try looking into sched_clock_cpu(), sched_clock_local() and
> sched_clock() to see whether anything odd stands out?
# git grep HAVE_UNSTABLE_SCHED_CLOCK arch/arm | wc -l
0
That code won't help if you don't enable it ;-)
John Stultz was also looking into making the kernel/sched_clock.c code
deal with short clocks.
WARNING: multiple messages have this Message-ID (diff)
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Russell King - ARM Linux <linux@arm.linux.org.uk>
Cc: Mikael Pettersson <mikpe@it.uu.se>,
Venkatesh Pallipadi <venki@google.com>,
Ingo Molnar <mingo@elte.hu>,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
John Stultz <johnstul@us.ibm.com>
Subject: Re: [BUG] 2.6.37-rc3 massive interactivity regression on ARM
Date: Wed, 08 Dec 2010 13:40:15 +0100 [thread overview]
Message-ID: <1291812015.28378.24.camel@laptop> (raw)
In-Reply-To: <20101205162151.GH9138@n2100.arm.linux.org.uk>
On Sun, 2010-12-05 at 16:21 +0000, Russell King - ARM Linux wrote:
> I'm not sure that's the correct fix - it looks like sched_clock_cpu()
> should already be preventing scheduler clock time going backwards.
>
> Hmm. IOP32x seems to have a 32-bit timer clocked at 200MHz. That means
> it wraps once every 21s. However, we have that converted to ns by an
> unknown multiplier and shift. It seems that those are chosen to
> guarantee that we will cover only 4s without wrapping in the clocksource
> conversion. Maybe that's not sufficient?
>
> Could you try looking into sched_clock_cpu(), sched_clock_local() and
> sched_clock() to see whether anything odd stands out?
# git grep HAVE_UNSTABLE_SCHED_CLOCK arch/arm | wc -l
0
That code won't help if you don't enable it ;-)
John Stultz was also looking into making the kernel/sched_clock.c code
deal with short clocks.
next prev parent reply other threads:[~2010-12-08 12:40 UTC|newest]
Thread overview: 102+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-27 15:16 [BUG] 2.6.37-rc3 massive interactivity regression on ARM Mikael Pettersson
2010-11-27 15:16 ` Mikael Pettersson
2010-12-05 12:32 ` Mikael Pettersson
2010-12-05 12:32 ` Mikael Pettersson
2010-12-05 13:17 ` Russell King - ARM Linux
2010-12-05 13:17 ` Russell King - ARM Linux
2010-12-05 14:19 ` Russell King - ARM Linux
2010-12-05 14:19 ` Russell King - ARM Linux
2010-12-05 16:07 ` Mikael Pettersson
2010-12-05 16:07 ` Mikael Pettersson
2010-12-05 16:21 ` Russell King - ARM Linux
2010-12-05 16:21 ` Russell King - ARM Linux
2010-12-08 12:40 ` Peter Zijlstra [this message]
2010-12-08 12:40 ` Peter Zijlstra
2010-12-08 12:55 ` Russell King - ARM Linux
2010-12-08 12:55 ` Russell King - ARM Linux
2010-12-08 14:04 ` Peter Zijlstra
2010-12-08 14:04 ` Peter Zijlstra
2010-12-08 14:28 ` Russell King - ARM Linux
2010-12-08 14:28 ` Russell King - ARM Linux
2010-12-08 14:44 ` Peter Zijlstra
2010-12-08 14:44 ` Peter Zijlstra
2010-12-08 15:05 ` Russell King - ARM Linux
2010-12-08 15:05 ` Russell King - ARM Linux
2010-12-08 15:43 ` Linus Walleij
2010-12-08 15:43 ` Linus Walleij
2010-12-08 20:42 ` john stultz
2010-12-08 20:42 ` john stultz
2010-12-08 23:31 ` Venkatesh Pallipadi
2010-12-08 23:31 ` Venkatesh Pallipadi
2010-12-09 12:52 ` Peter Zijlstra
2010-12-09 12:52 ` Peter Zijlstra
2010-12-09 17:43 ` Venkatesh Pallipadi
2010-12-09 17:43 ` Venkatesh Pallipadi
2010-12-09 17:55 ` Peter Zijlstra
2010-12-09 17:55 ` Peter Zijlstra
2010-12-09 18:11 ` Venkatesh Pallipadi
2010-12-09 18:11 ` Venkatesh Pallipadi
2010-12-09 18:55 ` Peter Zijlstra
2010-12-09 18:55 ` Peter Zijlstra
2010-12-09 22:21 ` Venkatesh Pallipadi
2010-12-09 22:21 ` Venkatesh Pallipadi
2010-12-09 23:16 ` Peter Zijlstra
2010-12-09 23:16 ` Peter Zijlstra
2010-12-09 23:35 ` Venkatesh Pallipadi
2010-12-09 23:35 ` Venkatesh Pallipadi
2010-12-10 10:08 ` Peter Zijlstra
2010-12-10 10:08 ` Peter Zijlstra
2010-12-10 13:17 ` Peter Zijlstra
2010-12-10 13:17 ` Peter Zijlstra
2010-12-10 13:27 ` Peter Zijlstra
2010-12-10 13:27 ` Peter Zijlstra
2010-12-10 13:47 ` Peter Zijlstra
2010-12-10 13:47 ` Peter Zijlstra
2010-12-10 16:50 ` Russell King - ARM Linux
2010-12-10 16:50 ` Russell King - ARM Linux
2010-12-10 16:54 ` Peter Zijlstra
2010-12-10 16:54 ` Peter Zijlstra
2010-12-10 17:18 ` Eric Dumazet
2010-12-10 17:18 ` Eric Dumazet
2010-12-10 17:49 ` Peter Zijlstra
2010-12-10 17:49 ` Peter Zijlstra
2010-12-10 18:14 ` Eric Dumazet
2010-12-10 18:14 ` Eric Dumazet
2010-12-10 18:39 ` Christoph Lameter
2010-12-10 18:39 ` Christoph Lameter
2010-12-10 18:46 ` Peter Zijlstra
2010-12-10 18:46 ` Peter Zijlstra
2010-12-10 19:51 ` Christoph Lameter
2010-12-10 19:51 ` Christoph Lameter
2010-12-10 20:07 ` Peter Zijlstra
2010-12-10 20:07 ` Peter Zijlstra
2010-12-10 20:23 ` Christoph Lameter
2010-12-10 20:23 ` Christoph Lameter
2010-12-10 20:32 ` Peter Zijlstra
2010-12-10 20:32 ` Peter Zijlstra
2010-12-10 20:39 ` Eric Dumazet
2010-12-10 20:39 ` Eric Dumazet
2010-12-10 20:49 ` Eric Dumazet
2010-12-10 20:49 ` Eric Dumazet
2010-12-10 21:09 ` Christoph Lameter
2010-12-10 21:09 ` Christoph Lameter
2010-12-10 21:22 ` Eric Dumazet
2010-12-10 21:22 ` Eric Dumazet
2010-12-10 21:45 ` Christoph Lameter
2010-12-10 21:45 ` Christoph Lameter
2010-12-10 17:56 ` Russell King - ARM Linux
2010-12-10 17:56 ` Russell King - ARM Linux
2010-12-10 18:10 ` Peter Zijlstra
2010-12-10 18:10 ` Peter Zijlstra
2010-12-10 18:43 ` Peter Zijlstra
2010-12-10 18:43 ` Peter Zijlstra
2010-12-10 19:17 ` Russell King - ARM Linux
2010-12-10 19:17 ` Russell King - ARM Linux
2010-12-10 19:37 ` Peter Zijlstra
2010-12-10 19:37 ` Peter Zijlstra
2010-12-10 19:25 ` Peter Zijlstra
2010-12-10 19:25 ` Peter Zijlstra
2010-12-13 14:33 ` Jack Daniel
2010-12-13 14:33 ` Jack Daniel
2010-12-06 21:29 ` Venkatesh Pallipadi
2010-12-06 21:29 ` Venkatesh Pallipadi
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