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Date: Fri, 21 May 2010 13:13:49 +0200
From: Jan Kiszka <jan.kiszka@siemens.com>
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Subject: [Qemu-devel] Re: [PATCH 1/2] trace: Add simple tracing support
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To: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Cc: Anthony Liguori <aliguori@us.ibm.com>, qemu-devel@nongnu.org, kvm@vger.kernel.org, Prerna Saxena <prerna@linux.vnet.ibm.com>

Stefan Hajnoczi wrote:
> Trace events should be defined in trace.h.  Events are written to
> /tmp/trace.log and can be formatted using trace.py.  Remember to add
> events to trace.py for pretty-printing.

When already writing to a file, why not reusing QEMU's logging
infrastructure ("log <foo>" / "-d foo")? Shouldn't make a huge
performance difference if the data is saved in clear-text.

Also, having support for ftrace's user space markers would be a very
nice option (only an option as it's Linux-specific), see
http://lwn.net/Articles/366796. This allows to correlate kernel events
(KVM as well as others) with what goes on in QEMU. It simply enables
integration with the whole kernel tracing infrastructure, e.g.
KernelShark (http://people.redhat.com/srostedt/kernelshark/HTML).

Jan

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