From: Peter Zijlstra <peterz@infradead.org>
To: "Liang, Kan" <kan.liang@intel.com>
Cc: "eranian@google.com" <eranian@google.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"mingo@redhat.com" <mingo@redhat.com>,
"paulus@samba.org" <paulus@samba.org>,
"acme@kernel.org" <acme@kernel.org>,
"ak@linux.intel.com" <ak@linux.intel.com>,
"Yan, Zheng" <zheng.z.yan@intel.com>
Subject: Re: [PATCH V5 14/16] perf, x86: enable LBR callstack when recording callchain
Date: Tue, 7 Oct 2014 17:25:28 +0200 [thread overview]
Message-ID: <20141007152528.GD5850@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <37D7C6CF3E00A74B8858931C1DB2F0770160F9C0@SHSMSX103.ccr.corp.intel.com>
On Tue, Oct 07, 2014 at 03:00:43AM +0000, Liang, Kan wrote:
>
>
> >
> > On Wed, Sep 10, 2014 at 10:09:11AM -0400, kan.liang@intel.com wrote:
> > > From: Kan Liang <kan.liang@intel.com>
> > >
> > > If a task specific event wants user space callchain but does not want
> > > branch stack sampling, enable the LBR call stack facility implicitly.
> > > The LBR call stack facility can help perf to get user space callchain
> > > in case of there is no frame pointer.
> > >
> > > Note: this feature only affects how to get user callchain. The kernel
> > > callchain is always got by frame pointers.
> >
> > Yeah, don't like this either. Suppose you have sane userspace (with
> > framepointers enabled) then you're now loosing the better option.
>
> FP is the first option. This patch tries to enable LBR call stack facility implicitly.
> Only when FP disabled or failed, we try to use LBR call stack.
> Please refer to the previous patch https://lkml.org/lkml/2014/9/10/376
Still makes for an entirely unpredictable situation. That way you never
quite know where your data came from.
next prev parent reply other threads:[~2014-10-07 15:25 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-10 14:08 [PATCH V5 00/16] perf, x86: Haswell LBR call stack support kan.liang
2014-09-10 14:08 ` [PATCH V5 01/16] perf, x86: Reduce lbr_sel_map size kan.liang
2014-09-24 10:50 ` Peter Zijlstra
2014-09-10 14:08 ` [PATCH V5 02/16] perf, core: introduce pmu context switch callback kan.liang
2014-09-24 11:23 ` Peter Zijlstra
2014-09-24 13:13 ` Peter Zijlstra
2014-09-10 14:09 ` [PATCH V5 03/16] perf, x86: use context switch callback to flush LBR stack kan.liang
2014-09-10 14:09 ` [PATCH V5 04/16] perf, x86: Basic Haswell LBR call stack support kan.liang
2014-09-10 14:09 ` [PATCH V5 05/16] perf, core: pmu specific data for perf task context kan.liang
2014-09-10 14:09 ` [PATCH V5 06/16] perf, core: always switch pmu specific data during context switch kan.liang
2014-09-10 14:09 ` [PATCH V5 07/16] perf, x86: allocate space for storing LBR stack kan.liang
2014-09-10 14:09 ` [PATCH V5 08/16] perf, x86: track number of events that use LBR callstack kan.liang
2014-09-24 12:53 ` Peter Zijlstra
2014-10-07 2:59 ` Liang, Kan
2014-10-07 15:19 ` Peter Zijlstra
2014-09-10 14:09 ` [PATCH V5 09/16] perf, x86: Save/resotre LBR stack during context switch kan.liang
2014-09-24 13:33 ` Peter Zijlstra
2014-09-10 14:09 ` [PATCH V5 10/16] perf, core: simplify need branch stack check kan.liang
2014-09-24 13:55 ` Peter Zijlstra
2014-09-10 14:09 ` [PATCH V5 11/16] perf, core: Pass perf_sample_data to perf_callchain() kan.liang
2014-09-24 14:15 ` Peter Zijlstra
2014-10-07 3:00 ` Liang, Kan
2014-10-07 15:24 ` Peter Zijlstra
2014-10-07 15:50 ` Liang, Kan
2014-10-07 16:29 ` Peter Zijlstra
2014-09-10 14:09 ` [PATCH V5 12/16] perf, x86: use LBR call stack to get user callchain kan.liang
2014-09-10 14:09 ` [PATCH V5 13/16] perf, x86: re-organize code that implicitly enables LBR/PEBS kan.liang
2014-09-10 14:09 ` [PATCH V5 14/16] perf, x86: enable LBR callstack when recording callchain kan.liang
2014-09-24 14:21 ` Peter Zijlstra
2014-10-07 3:00 ` Liang, Kan
2014-10-07 15:25 ` Peter Zijlstra [this message]
2014-10-07 16:04 ` Liang, Kan
2014-09-10 14:09 ` [PATCH V5 15/16] perf, x86: disable FREEZE_LBRS_ON_PMI when LBR operates in callstack mode kan.liang
2014-09-10 14:09 ` [PATCH V5 16/16] perf, x86: Discard zero length call entries in LBR call stack kan.liang
-- strict thread matches above, loose matches on Subject: below --
2014-07-07 6:28 [PATCH v5 00/16] perf, x86: Haswell LBR call stack support Yan, Zheng
2014-07-07 6:28 ` [PATCH v5 14/16] perf, x86: enable LBR callstack when recording callchain Yan, Zheng
2001-01-08 2:31 [PATCH V5 10/16] perf, core: simplify need branch stack check kan.liang
2001-01-08 2:32 ` [PATCH V5 14/16] perf, x86: enable LBR callstack when recording callchain kan.liang
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