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Date: Tue, 19 Oct 2010 16:38:49 +0200
From: Jan Kiszka <jan.kiszka@siemens.com>
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Subject: [Qemu-devel] Re: Tracing block devices
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To: "Richard W.M. Jones" <rjones@redhat.com>
Cc: Stefan Hajnoczi <stefanha@gmail.com>, Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>, qemu-devel <qemu-devel@nongnu.org>

Am 19.10.2010 16:29, Richard W.M. Jones wrote:
> On Tue, Oct 19, 2010 at 03:59:36PM +0200, Jan Kiszka wrote:
>> Once we have "-trace events=...", defining the list of active
>> tracepoints before starting qemu will be trivial (e.g. via a config
>> file). Of course, this requires that all tracepoints are built-in...
> 
> Sorry that I've not been following this very closely, but does this
> sort of thing allow tracing reads and writes to block devices?  Am I
> right in thinking that if a tracepoint existed in the right place, one
> could get a log file from that which could be post-processed in
> another tool?
> 
> cf:
> http://rwmj.wordpress.com/2010/10/05/visualizing-reads-writes-and-alignment/#content
> 
> Rich.
> 

Yes. The block layer is instrumented, not sure if already sufficiently,
but you may simply want to try the simpletrace backend and inspect the
result via its postprocessor (simpletrace.py).

Jan

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