linux-kernel - Re: [BISECTED] 2.6.35.*: horrible (exponential? >linear) slowdown to unusability (HPET)

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Message-ID: <8762yd8ihs.fsf@spindle.srvr.nix>
Date:	Fri, 10 Sep 2010 21:13:19 +0100
From:	Nix <nix@...eri.org.uk>
To:	Artur Skawina <art.08.09@...il.com>
Cc:	Jiri Slaby <jirislaby@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Venkatesh Pallipadi <venki@...gle.com>,
	Damien Wyart <damien.wyart@...e.fr>,
	John Drescher <drescherjm@...il.com>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [BISECTED] 2.6.35.*: horrible (exponential? >linear) slowdown to unusability (HPET)

On 10 Sep 2010, Artur Skawina outgrape:

> On 09/10/10 11:41, Jiri Slaby wrote:
>> AFAIU, clocksource=jiffies shouldn't fix this issue. If that's the case
>> we have another 2.6.32->2.6.33 regression (and I will report it
>> separately). People report the system is unusable (sleepers are not
>> woken), unless clocksource=jiffies, clocksource=tsc or nolapic_timer is
>> used or a key pressed (i.e. some HW interrupt):
>> https://bugzilla.novell.com/show_bug.cgi?id=579932
>> (there is also a report with 2.6.35.3 vanilla)
>
> I saw this first in v2.6.35-rc4. The symptom is that suddenly everything
> stops and the only way to make things progress is to generate some events.
> Apps that are waiting for a timeout aren't woken up unless you press a key
> etc. After a few minutes (and lots of key presses ;) ) the machine usually
> recovers, leaving no trace in logs.

In NOHZ mode, my (consistently affected) system never recovers. In !NOHZ
mode, it never locks up, although timings are shot all to hell.
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