lkml.org 
[lkml]   [2014]   [Feb]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH v3 00/14] perf, x86: Haswell LBR call stack support
On Wed, Feb 26, 2014 at 10:55 AM, Andi Kleen <andi@firstfloor.org> wrote:
>> I'm suggesting a perf event option, just like the way that PEBS works.
>
> Right now it's a somewhat experimental feature and just having
> the sysctl is fine. If it turns out that is what everyone uses
> such an option could be still added later.

I'm a bit worried that the syscall will be stuck as ABI forever,
though. Its presence will make adding a different configuration
mechanism awkward.

>
> I suspect most people would still use FP if they can, just use
> the LBRs if that doesn't work.

I wonder if anyone who uses perf for userspace profiling *ever* uses
FP and gets away with it. There's precious little userspace software
compiled with frame pointers these days on most architectures.

I have a concrete reason for this question: it would be nice to
compile the vDSO with frame pointers off. IIRC there would be a
significant performance gain, and I think the only thing that would
break is perf. But it looks like perf will have nice elfutils unwind
support in 3.15, and if FP support is useless anyway...

--Andy


\
 
 \ /
  Last update: 2014-02-26 20:41    [W:0.092 / U:0.408 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site