Re: [PATCH 00/12] perf_events: add support for sampling taken branches (v2)

[Peter Zijlstra <peterz@infradead.org>]

On Tue, 2011-12-06 at 09:49 +0000, Will Deacon wrote:
> On Mon, Dec 05, 2011 at 10:39:26PM +0000, Peter Zijlstra wrote:
> > On Fri, 2011-10-14 at 14:37 +0200, Stephane Eranian wrote:
> > > This patchset adds an important and useful new feature to
> > > perf_events: branch stack sampling. In other words, the
> > > ability to capture taken branches into each sample.
> > > 
> > Other than the few comments given it all looks good. My main worry is
> > the Intel only aspect, I'd really love for there to be another platform
> > that could implement at least part of this.
> 
> I discussed this with Stephane in Prague and, although it would be lovely to
> have this on ARM, we simply don't have the hardware to do it. So the nature
> of series does seem to be x86-centric unless there's way to do a watered
> down version in software.

The only way to do this in software would be like
CONFIG_PROFILE_ALL_BRANCHES and that's horrid (and kernel only).

But there's more than Intel & ARM, but it looks like PPC doesn't have
this either and I suspect MIPS and SPARC don't either, which doesn't
leave us with much else.

So I guess we should just go ahead and merge this and hope more hardware
grows this feature in a compatible enough manner.