Date: Sun, 2 Dec 2007 21:45:59 +0100
From: Ingo Molnar <mingo@elte.hu>
To: =?iso-8859-1?Q?J=F6rn?= Engel <joern@logfs.org>
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
Subject: Re: [BUG] Strange 1-second pauses during Resume-from-RAM
Message-ID: <20071202204559.GA28550@elte.hu>
References: <20071201205456.GA8231@elte.hu> <20071201234112.GA7209@lazybastard.org> <20071202085607.GA28966@elte.hu> <20071202113143.GA9378@lazybastard.org> <20071202135711.GA20434@elte.hu> <20071202141117.GB9516@lazybastard.org> <20071202154746.GA27069@elte.hu> <20071202195501.GB10657@lazybastard.org> <20071202200722.GA12101@elte.hu> <20071202203016.GC10657@lazybastard.org>
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* J?rn Engel <joern@logfs.org> wrote:

> > oprofile helps if you can reliably reproduce the slowdown in a loop 
> > or for a long amount of time, with lots of CPU utilization - and 
> > then it's also lower overhead. The tracer can be used to capture 
> > rare or complex events, and gives the full flow control and what is 
> > happening within the kernel.
> 
> Such a trace would be useful indeed.  But so far the patch has only 
> given me grief and nothing remotely like useful output.  Maybe I 
> should simply use the complete -rt patch instead of debugging the 
> broken-out latency-tracer patch.

to capture that trace i did not use -rt, i just patched latest -git 
with:

  http://people.redhat.com/mingo/latency-tracing-patches/latency-tracing-v2.6.24-rc3.combo.patch

(this has your fixes included already)

have done:

  echo 1 > /proc/sys/kernel/mcount_enabled

and have run:

  ./trace-cmd sleep 1 > trace.txt

  http://people.redhat.com/mingo/latency-tracing-patches/trace-cmd.c

to capture a 1 second trace of what the system is doing. I think your 
troubles are due to running it within a qemu guest - that is not a 
typical utilization so you are on unchartered waters.

	Ingo
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