linux-kernel - Re: [Regression] 2.6.24-git3: Major annoyance during suspend/hibernation on x86-64 (bisected)

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Message-Id: <200801312154.33754.rjw@sisk.pl>
Date:	Thu, 31 Jan 2008 21:54:32 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Ingo Molnar <mingo@...e.hu>, Steven Rostedt <srostedt@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Dmitry Adamushko <dmitry.adamushko@...il.com>
Subject: Re: [Regression] 2.6.24-git3: Major annoyance during suspend/hibernation on x86-64 (bisected)

On Thursday, 31 of January 2008, Peter Zijlstra wrote:
> 
> On Mon, 2008-01-28 at 02:26 +0100, Rafael J. Wysocki wrote:
> > On Sunday, 27 of January 2008, Ingo Molnar wrote:
> > > 
> > > * Rafael J. Wysocki <rjw@...k.pl> wrote:
> > > 
> > > > Hi,
> > > > 
> > > > 2.6.24-git3 adds a 5 - 10 sec delay to the suspend and hibernation 
> > > > code paths (probably related to the disabling of nonboot CPUs), which 
> > > > is !@...^&*() annoying.
> > > > 
> > > > It's 100% reproducible on my HP nx6325 and bisection idendified the 
> > > > following commit as the first bad one:
> > > > 
> > > > commit 764a9d6fe4b52995c8aba277e3634385699354f4
> > > > Author: Steven Rostedt <srostedt@...hat.com>
> > > > Date:   Fri Jan 25 21:08:04 2008 +0100
> > > > 
> > > >     sched: track highest prio task queued
> > > 
> > > hm, this patch is a NOP, so it's weird that it has an effect.
> > > 
> > > Do you have serial logging enabled perhaps? If the following WARN_ON() 
> > > triggers:
> > > 
> > > +               WARN_ON(p->prio < rq->rt.highest_prio);
> > > 
> > > then perhaps that can cause a 5-10 seconds delay. (that's how much time 
> > > it takes to printk a warning on the slowest serial settings)
> > > 
> > > but if you use suspend, then any such printks would be preserved in the 
> > > dmesg, right? If the WARN_ON() triggers, and if you remove it, do things 
> > > get faster?
> > 
> > No, this isn't the WARN_ON().
> > 
> > > this does have the feel of being scheduling related, but are you 
> > > absolutely sure about the precise identity of the patch?
> > 
> > Actually, not quite.  That's why I have verified it and found that another
> > patch is really responsible for the issue, namely:
> > 
> > commit 82a1fcb90287052aabfa235e7ffc693ea003fe69
> > Author: Ingo Molnar <mingo@...e.hu>
> > Date:   Fri Jan 25 21:08:02 2008 +0100
> > 
> >     softlockup: automatically detect hung TASK_UNINTERRUPTIBLE tasks
> > 
> > Reverting this commit (it reverts with some minor modifications) fixes the
> > problem for me.
> 
> I can seem to reproduce this:
> 
> [root@...eron cpu1]# time echo 0 > online
> 
> real    0m6.230s
> user    0m0.000s
> sys     0m0.010s
> [root@...eron cpu1]# echo 1 > online
> [root@...eron cpu1]# time echo 0 > online
> 
> real    0m7.966s
> user    0m0.000s
> sys     0m0.011s
> 
> 
> I'll have a look at it.

Much appreciated, thanks!
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