lkml.org 
[lkml]   [2012]   [Jun]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: perf support user-space hw_breakpoint?
From
Hi,

On Thu, Jun 28, 2012 at 10:20 AM, Namhyung Kim <namhyung@kernel.org> wrote:
> On Thu, 28 Jun 2012 09:02:02 +0800, Jovi Zhang wrote:
>> On Mon, Jun 25, 2012 at 4:26 PM, Namhyung Kim <namhyung@kernel.org> wrote:
>>> BTW, when I perf record on a hwbp, it failed with ENOSPC.
>>> I guess it's because each per-task-per-cpu event tried to
>>> create an event so it'd get more than supported by h/w.
>>> The strace told me that the fifth call to perf_event_open
>>> failed on my 6-core machine.
>>>
>> I have same result as you in my linux box.
>> This should be a bug cause by commit d1cb9f(perf target: Add uses_mmap field)
>>
>> Namhyung, How about below patch?
>>
>
> NAK. This uses_mmap field is needed to setup per-task-per-cpu events for
> perf record (mostly). Without it, perf suffered from severe scalability
> issues. Maybe we can change it not to create per-task-per-cpu events iff
> for hwbp events only, but I'm not sure it's the right thing.
>
> Thanks,
> Namhyung
>
perf tool create cpumaps and threadmaps for evlist, not for evsel, this means
we cannot easily create a dummy cpumaps for hwbp event even when
evlist include hwbp type evsel.

Any ideas?

.jovi


\
 
 \ /
  Last update: 2012-06-28 07:01    [W:0.074 / U:1.460 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site