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Re: [Qemu-devel] Call Trace for QEMU functions

From: Alex Bennée
Subject: Re: [Qemu-devel] Call Trace for QEMU functions
Date: Thu, 30 Jul 2015 16:04:10 +0100

Peter Maydell <address@hidden> writes:

> On 30 July 2015 at 13:20, Naman patel <address@hidden> wrote:
>> Hi,
>>      I have compiled QEMU (2.0) for x86_64 on Fedora 22 with tracing enabled
>> and the tracing option I chose was dtrace. I have this script called
>> callTrace.stp in which I try and get the Call Trace of the function
>> helper_invlpg and later tlb_flush.  But I am not able to get the function
>> name of the caller function and the call trace depth is only limited to 2.
> The helper_invlpg function is called directly from code generated
> by QEMU's built-in JIT, not from any other C function.
> If you use a newer version of QEMU than 2.0 then I think we have
> fixed some of the stack frame information up so that you can
> get a backtrace that looks like:
>  * helper function
>  * [generated code]
>  * QEMU execution loop code that handles executing guest code
>  * other QEMU functions
> This is not likely to be very useful for profiling why or when
> we're calling a particular helper function, though.

With the perf JIT patch you can get a better handle on the profile. I'll
see if I can re-spin them tomorrow for the latest tree.

> thanks
> -- PMM

Alex Bennée

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