Re: [PATCH] perf: implement recording/reporting per-cpu samples

[Arun Sharma]

On Tue, May 04, 2010 at 11:16:38AM +0200, Peter Zijlstra wrote:
> > In a shared multi-core environment, users want to analyze why their
> > program was slow. In particular, if the code ran slower only on
> > certain CPUs due to interference from other programs or kernel
> > threads, they want to know that.
> 
> But for that you use perf record -a, right? So you record all cpus
> allways -- otherwise there is no telling what was happening to make it
> go slow.

The updated patch records the CPU only in the system_wide mode.

> 
> > But that's just our use case. The patch is mostly about --sort cpu
> > option. If you want to drop the part that enables PERF_SAMPLE_CPU by
> > default, that's fine by me.
> 
> Right, it would be very nice if we can avoid growing the default sample
> size. Also, your changelog needs work, please explain the full usecase
> that goes with this feature.
> 
> Explain the thing you're wanting to measure, explain the implementation
> and maybe give a short example.

Updated changelog as well.

 -Arun