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

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Date:	Wed, 28 Aug 2013 10:27:03 -0300
From:	Arnaldo Carvalho de Melo <acme@...hat.com>
To:	David Ahern <dsahern@...il.com>
Cc:	Stephane Eranian <eranian@...gle.com>,
	linux-kernel@...r.kernel.org, peterz@...radead.org, mingo@...e.hu,
	sukadev@...ux.vnet.ibm.com, jolsa@...hat.com, ak@...ux.intel.com
Subject: Re: [PATCH] perf mem: add priv level filtering support

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

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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