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From: Alex =?utf-8?Q?Benn=C3=A9e?= <alex.bennee@linaro.org>
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Date: Fri, 17 Oct 2014 11:43:04 +0100
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Subject: Re: [Qemu-devel] Counting barrier instructions in ARM
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To: Pranith Kumar <bobby.prani@gmail.com>
Cc: Peter Maydell <peter.maydell@linaro.org>, QEMU Developers <qemu-devel@nongnu.org>


Pranith Kumar <bobby.prani@gmail.com> writes:

> Hi Peter,
>
> On Thu, Oct 16, 2014 at 4:05 AM, Peter Maydell <peter.maydell@linaro.org> wrote:
>> On 16 October 2014 03:45, Pranith Kumar <bobby.prani@gmail.com> wrote:
>>> The problem I am facing is that this seems to be crashing when run with a
>>> multi-threaded executable.
>>
>> This is nothing to do with your changes -- user-mode QEMU does not
>> support multi-threaded guest executables. QEMU may crash, hang,
>> or stop with an assertion failure, fairly randomly. Don't try
>> to run multithreaded guests :-)
>
> OK, I will try to gather the statistics in system mode. Is there any
> way to indicate from within the system to  qemu to start collecting the stats?
>
> I dont want to collect the stats for bootup and other unrelated code
> paths.

You could enable CONTEXTIDR in the kernel and then make your counts
against an array indexed by it. I've used that technique before to
profile guest hot-blocks and work out which guest PID was responsible.

-- 
Alex Bennée