linux-kernel - Disregard: was Re: large intermittent latency spike 2.6.28 (and 2.6.27.10), bisect commit ca7e716c7833aeaeb8fedd6d004c5f5d5e14d325 -> Revert "sched_clock: prevent scd->clock from moving backwards"

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Message-ID: <495B40C1.4080305@jaysonking.com>
Date:	Wed, 31 Dec 2008 03:52:01 -0600
From:	Jayson King <dev@...sonking.com>
To:	linux-kernel@...r.kernel.org
CC:	mingo@...e.hu, torvalds@...ux-foundation.org,
	a.p.zijlstra@...llo.nl, shaggy@...ux.vnet.ibm.com, rjw@...k.pl,
	fabio.comolli@...il.com
Subject: Disregard: was Re: large intermittent latency spike 2.6.28 (and 2.6.27.10),
 bisect commit ca7e716c7833aeaeb8fedd6d004c5f5d5e14d325 -> Revert "sched_clock:
 prevent scd->clock from moving backwards"

> I noticed large latency spikes in 2.6.28 (and 2.6.27.10) which would 
> make the system unresponsive for minutes at a time (alt+Fn switching 
> wouldn't even work) when the system is under load. I could trigger the 
> latency by running a large make -j 3. Sometimes it would trigger in a 
> few seconds other times it would take a few minutes.
>
> I bisected it in 2.6.27.10 to d9a888b061f55534016d2d86a21639948312a117 
> -> Revert "sched_clock: prevent scd->clock from moving backwards" 
> (ca7e716c7833aeaeb8fedd6d004c5f5d5e14d325 in 2.6.28) and reverting it 
> in 2.6.28 make the latency spike go away. At least, so far no spike in 
> over 24 hours.
Please disregard this. I just had a latency spike again, so this is not 
the change I'm looking for... I'll need to look for what is causing it 
again, apparently not only the make -j 3 I thought, and do another test.

Jayson

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