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

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Message-Id: <1195213993.4037.21.camel@Knoppix>
Date:	Fri, 16 Nov 2007 06:53:13 -0500
From:	Mike Galbraith <efault@....de>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Mark Lord <lkml@....ca>, 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, Len Brown <lenb@...nel.org>
Subject: Re: [BUG] Strange 1-second pauses during Resume-from-RAM

On Fri, 2007-11-16 at 12:23 +0100, Ingo Molnar wrote:
> * Ingo Molnar <mingo@...e.hu> wrote:
> 
> > once that tracer bug was fixed, the best method to generate a trace 
> > was to do this:
> > 
> >    echo 1 > /proc/sys/kernel/stackframe_tracing
> >    echo 1 > /proc/sys/kernel/syscall_tracing
> >    ./trace-cmd bash -c "echo mem > /sys/power/state" > trace.txt
> 
> so here's an UP suspend+resume trace i did:
> 
>   http://redhat.com/~mingo/latency-tracing-patches/misc/trace-suspend-long.txt.bz2
> 
> tons of detail - which might be interesting to other folks as well. Fact 
> is, our suspend-to-RAM+resume cycle is very, very slow, even on fast 
> hardware - and this trace shows all the reasons why.
> 
> This was a fully cached system - i.e. i've done a suspend+resume before 
> to warm up the caches. (not that suspend+resume does much IO normally.)
> 
> The trace shows that a suspend+resume cycle is 7.95 seconds long 
> (without counting the time the box spent suspended) - ouch! This was a 
> T60 with Core2Duo 1.83GHz.

Ouch?  That's an order of magnitude faster than my 3GHz P4 :)

	-Mike

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