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

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Date:	Wed, 28 Aug 2013 15:38:28 +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

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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