lkml.org 
[lkml]   [2012]   [Feb]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] perf tools: fix guest mode monitoring on AMD
On 2/27/12 10:52 AM, Stephane Eranian wrote:
> On Mon, Feb 27, 2012 at 6:47 PM, David Ahern<dsahern@gmail.com> wrote:
>> On 2/27/12 10:33 AM, Stephane Eranian wrote:
>>>
>>> Commit:
>>>
>>> 1aed267 perf kvm: Do guest-only counting by default
>>>
>>> introduced a bug on AMD systems whereby simple commands:
>>>
>>> $ perf stat ls
>>> Performance counter stats for 'ls':
>>> 0 cycles # 0.000 GHz
>>> 0.003704596 seconds time elapsed
>>>
>>> would not count anything anymore. Same results for perf record.
>>>
>>> I tracked it down to guest mode exclusion being enabled
>>> by default leading to attr->exclude_guest = 1. When
>>> not operating under any sort of virtualization, this
>>> causes the PMU not to count anything.
>>>
>>> The fix disables guest exclusion by default.
>>>
>>> Signed-off-by: Stephane Eranian<eranian@google.com>
>>> ---
>>>
>>> diff --git a/tools/perf/util/util.c b/tools/perf/util/util.c
>>> index 8109a90..c1017b3 100644
>>> --- a/tools/perf/util/util.c
>>> +++ b/tools/perf/util/util.c
>>> @@ -6,7 +6,7 @@
>>> * XXX We need to find a better place for these things...
>>> */
>>> bool perf_host = true;
>>> -bool perf_guest = false;
>>> +bool perf_guest = true;
>>
>>
>> This was recently reverted to false by
>> c4a7dca92bbb9881a5d678720f1d0c2153499749
>>
>> See: https://lkml.org/lkml/2012/2/8/234
>>
> Yeah, but that causes simple commands such as "perf stat -e cycles ls"
> to return 0 count.
>
> So either you get a segfault or you get zero count. There is something
> else going on here...

agreed. Did you try reverting exclude_guest by default?



\
 
 \ /
  Last update: 2012-02-27 19:03    [W:0.051 / U:12.368 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site