From: Andi Kleen <ak@linux.intel.com>
To: Stephane Eranian <eranian@google.com>
Cc: "Yan, Zheng" <zheng.z.yan@intel.com>,
LKML <linux-kernel@vger.kernel.org>,
Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [PATCH V2 6/7] perf, x86: Use LBR call stack to get user callchain
Date: Wed, 24 Oct 2012 05:41:14 -0700 [thread overview]
Message-ID: <20121024124114.GV2095@tassilo.jf.intel.com> (raw)
In-Reply-To: <CABPqkBQ7dOFpGOLu_Dbyr=HPeBj6mC8Roov7ZpD6v6qUO2JsFA@mail.gmail.com>
> But isn't the whole point of the patch to hide LBR cstack from users so they
> won't know they're using it for user cstack?
The point of the patch is to get user backtraces where you can't
get them today.
>
> To disable it in sysfs, I need to know it's being used in the first place.
You can always disable unconditionally it if you want to use LBR.
> I think in x86_pmu_hw_config(), you could simply check the priv level
> restrictions on the event. If exclude_user is set, then don't active LBR cstack
> and that's it. That's what I was trying to get to...
Ok that sounds reasonable. Yes it only makes sense for user sampling
currently. However the restriction may be fixed at some point, then
it could be also used for the kernel.
-Andi
--
ak@linux.intel.com -- Speaking for myself only
next prev parent reply other threads:[~2012-10-24 12:51 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-24 5:59 [PATCH V2 0/7] perf, x86: Haswell LBR call stack support Yan, Zheng
2012-10-24 5:59 ` [PATCH V2 1/7] perf, x86: Reduce lbr_sel_map size Yan, Zheng
2012-10-24 7:28 ` Stephane Eranian
2012-10-24 7:49 ` Yan, Zheng
2012-10-24 8:15 ` Stephane Eranian
2012-10-24 8:23 ` Yan, Zheng
2012-10-24 8:37 ` Yan, Zheng
2012-10-24 8:53 ` Stephane Eranian
2012-10-24 5:59 ` [PATCH V2 2/7] perf, x86: Basic Haswell LBR call stack support Yan, Zheng
2012-10-24 5:59 ` [PATCH V2 3/7] perf, x86: Introduce x86 special perf event context Yan, Zheng
2012-10-24 5:59 ` [PATCH V2 4/7] perf, x86: Save/resotre LBR stack during context switch Yan, Zheng
2012-10-24 5:59 ` [PATCH V2 5/7] perf, core: Pass perf_sample_data to perf_callchain() Yan, Zheng
2012-10-24 5:59 ` [PATCH V2 6/7] perf, x86: Use LBR call stack to get user callchain Yan, Zheng
2012-10-24 8:57 ` Stephane Eranian
2012-10-24 11:23 ` Yan, Zheng
2012-10-24 11:47 ` Stephane Eranian
2012-10-24 11:52 ` Yan, Zheng
2012-10-24 12:11 ` Stephane Eranian
2012-10-24 12:21 ` Stephane Eranian
2012-10-24 12:31 ` Andi Kleen
2012-10-24 12:36 ` Stephane Eranian
2012-10-24 12:41 ` Andi Kleen [this message]
2012-10-24 12:46 ` Yan, Zheng
2012-10-24 5:59 ` [PATCH V2 7/7] perf, x86: Discard zero length call entries in LBR call stack Yan, Zheng
2012-10-25 9:12 ` Namhyung Kim
2012-10-24 8:49 ` [PATCH V2 0/7] perf, x86: Haswell LBR call stack support Stephane Eranian
-- strict thread matches above, loose matches on Subject: below --
2013-07-01 7:23 [PATCH v2 " Yan, Zheng
2013-07-01 7:23 ` [PATCH v2 6/7] perf, x86: Use LBR call stack to get user callchain Yan, Zheng
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