linux-kernel - Re: [PATCH] perf mem: add priv level filtering support

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Message-ID: <CABPqkBTafXRdE4H+Y07+3b+jbR3AKa1zEKRXJz=nZLb5sBN77w@mail.gmail.com>
Date:	Wed, 28 Aug 2013 15:53:50 +0200
From:	Stephane Eranian <eranian@...gle.com>
To:	Arnaldo Carvalho de Melo <acme@...hat.com>
Cc:	David Ahern <dsahern@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	"mingo@...e.hu" <mingo@...e.hu>,
	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>,
	Jiri Olsa <jolsa@...hat.com>,
	"ak@...ux.intel.com" <ak@...ux.intel.com>
Subject: Re: [PATCH] perf mem: add priv level filtering support

Arnaldo,

So I just checked perf top and those 2 options are
doing user level filtering of the samples. This is different
from what I want which is hardware level filtering if avail.



On Wed, Aug 28, 2013 at 3:38 PM, Stephane Eranian <eranian@...gle.com> wrote:
> On Wed, Aug 28, 2013 at 3:27 PM, Arnaldo Carvalho de Melo
> <acme@...hat.com> wrote:
>> Em Mon, Aug 26, 2013 at 04:21:44PM -0600, David Ahern escreveu:
>>> On 8/26/13 7:11 AM, Stephane Eranian wrote:
>>
>>> >This patch adds the -u -and -k options to perf to allow
>>> >filtering of load/store sampling based on priv levels.
>>> >This may not be supported by all HW platforms.
>>
>>
>>> >+++ b/tools/perf/Documentation/perf-mem.txt
>>> >+-k::
>>> >+    Only sample loads/stores at the user level (default: user + kernel)
>>> >+-u::
>>> >+    Only sample loads/stores at the kernel level (default: user + kernel)
>>
>>> Are the descriptions backwards? In the commit message yuo have -u
>>> means user level and -k means kernel level; the help message here
>>> seems backwards.
>>
>> Looks like it is reversed, yes.
>>
>>> >+    OPT_BOOLEAN('u', "user-level", &mem.user, "include user-level accesses"),
>>> >+    OPT_BOOLEAN('k', "kernel-level", &mem.kernel, "include kernel-level accesses"),
>>
>> And its not clear to say that using -u will _exclude_ kernel samples,
>> just that it includes user samples, perf top has:
>>
>>     -K, --hide_kernel_symbols   hide kernel symbols
>>     -U, --hide_user_symbols     hide user symbols
>>
>> So perhaps we should change both to (and add this to 'report' as well):
>>
>>     -U, --hide_kernel_symbols   hide kernel symbols
>>     -K, --hide_user_symbols     hide user symbols
>>
>
> Well, I don't know what perf top does here but I don't want to hide
> the samples. I simply don't want to collect them (do not appear
> in the perf.data file). If that's what is happening in perf top, then
> I'll be glad to use the same options.
>
>
>> To state that:
>>
>>         perf top -K
>> and
>>         perf top --hide_user_symbols
>>
>> Are equivalent and asks for 'kernel only' samples, like it seems its the
>> intent (filtering) of Stephane here, and seems to clarify things?
>>
>> - Arnaldo
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