linux-kernel - Re: [BUG] Strange 1-second pauses during Resume-from-RAM

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Date:	Thu, 15 Nov 2007 20:34:24 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Mark Lord <lkml@....ca>
Cc:	Pavel Machek <pavel@....cz>, Mark Lord <liml@....ca>,
	Thomas Gleixner <tglx@...utronix.de>, len.brown@...el.com,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-pm@...ts.linux-foundation.org,
	rjw@...k.pl
Subject: Re: [BUG] Strange 1-second pauses during Resume-from-RAM


* Mark Lord <lkml@....ca> wrote:

>> Can you try nohz=off highres=off? Strange stuff is happening with 
>> nohz.
>
> (added Ingo to CC: list: maybe this is some weird interaction with CFS 
> and jiffies being reset to 0 on resume ??)

hm, CFS should have no impact here. To see what's happening you could 
try to use the latency tracer of the -rt patch and do a cross-resume 
trace.

pick up the latest latency tracer patch from:

  http://redhat.com/~mingo/private/latency-tracer-v2.6.24-rc2-git5-combo.patch

apply it and enable CONFIG_FUNCTION_TRACING, then pick up trace-cmd.c:

  http://redhat.com/~mingo/private/trace-cmd.c

and do something like:

  ./trace-cmd pm-suspend > trace.txt

or:

  ./trace-cmd /bin/bash -c "echo ram > /sys/power/state" > trace.txt

this should trigger suspend - then you should do the resume. If 
everything goes well then trace.txt should contain a pretty large trace 
of all the stuff we do during a suspend+resume.

and wait for such a pause and send us the resulting trace.txt.

if it's an SMP box then first do:

  echo 1 > /proc/sys/kernel/trace_all_cpus

to get a global trace. Let me know if something doesnt work with this 
scheme.

	Ingo
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