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Subject: Re: [BUG] Strange 1-second pauses during Resume-from-RAM
From: Mike Galbraith <efault@gmx.de>
To: Ingo Molnar <mingo@elte.hu>
Cc: Mark Lord <lkml@rtr.ca>, Pavel Machek <pavel@ucw.cz>,
       Mark Lord <liml@rtr.ca>, Thomas Gleixner <tglx@linutronix.de>,
       len.brown@intel.com, Andrew Morton <akpm@linux-foundation.org>,
       linux-kernel@vger.kernel.org, linux-pm@lists.linux-foundation.org,
       rjw@sisk.pl, Len Brown <lenb@kernel.org>
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Date: Fri, 16 Nov 2007 06:53:13 -0500
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On Fri, 2007-11-16 at 12:23 +0100, Ingo Molnar wrote:
> * Ingo Molnar <mingo@elte.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