From: Peter Zijlstra <peterz@infradead.org>
To: "Yan, Zheng" <zheng.z.yan@intel.com>
Cc: linux-kernel@vger.kernel.org, mingo@kernel.org,
eranian@google.com, andi@firstfloor.org
Subject: Re: [PATCH 4/7] perf, x86: Save/resotre LBR stack during context switch
Date: Wed, 26 Jun 2013 13:47:04 +0200 [thread overview]
Message-ID: <20130626114704.GF28407@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <1372150039-15151-5-git-send-email-zheng.z.yan@intel.com>
On Tue, Jun 25, 2013 at 04:47:16PM +0800, Yan, Zheng wrote:
> From: "Yan, Zheng" <zheng.z.yan@intel.com>
>
> When the LBR call stack is enabled, it is necessary to save/restore
> the stack on context switch. The solution is saving/restoring the
> stack to/from task's perf event context. If task has no perf event
> context, just flush the stack on context switch.
So I have some problems with this; suppose the LBR is shared between a
cpu and a task event, when the task switches back in, it will over-write
the LBR content with old stuff.
In that case the CPU event's LBR stack can be actively wrong, as opposed
to being empty.
next prev parent reply other threads:[~2013-06-26 15:24 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-25 8:47 [PATCH 0/7] perf, x86: Haswell LBR call stack support Yan, Zheng
2013-06-25 8:47 ` [PATCH 1/7] perf, x86: Reduce lbr_sel_map size Yan, Zheng
2013-06-25 12:33 ` Stephane Eranian
2013-06-26 6:05 ` Yan, Zheng
2013-06-25 8:47 ` [PATCH 2/7] perf, x86: Basic Haswell LBR call stack support Yan, Zheng
2013-06-25 12:37 ` Stephane Eranian
2013-06-26 2:42 ` Yan, Zheng
2013-06-25 8:47 ` [PATCH 3/7] perf, x86: Introduce x86 special perf event context Yan, Zheng
2013-06-25 8:47 ` [PATCH 4/7] perf, x86: Save/resotre LBR stack during context switch Yan, Zheng
2013-06-26 11:47 ` Peter Zijlstra [this message]
2013-06-25 8:47 ` [PATCH 5/7] perf, core: Pass perf_sample_data to perf_callchain() Yan, Zheng
2013-06-25 8:47 ` [PATCH 6/7] perf, x86: Use LBR call stack to get user callchain Yan, Zheng
2013-06-26 9:00 ` Stephane Eranian
2013-06-26 12:42 ` Stephane Eranian
2013-06-26 12:45 ` Stephane Eranian
2013-06-27 1:52 ` Yan, Zheng
2013-06-27 1:40 ` Yan, Zheng
2013-06-27 8:58 ` Stephane Eranian
2013-06-28 2:24 ` Yan, Zheng
2013-06-25 8:47 ` [PATCH 7/7] perf, x86: Discard zero length call entries in LBR call stack Yan, Zheng
2013-06-25 12:40 ` [PATCH 0/7] perf, x86: Haswell LBR call stack support Stephane Eranian
2013-06-25 15:27 ` Andi Kleen
2013-06-25 15:30 ` Andi Kleen
2013-06-26 11:54 ` Peter Zijlstra
2013-06-26 16:40 ` Andi Kleen
2013-06-26 16:48 ` Stephane Eranian
2013-06-27 8:07 ` Yan, Zheng
2013-06-26 12:07 ` Peter Zijlstra
2013-06-26 16:59 ` Andi Kleen
2013-06-26 17:11 ` Peter Zijlstra
-- strict thread matches above, loose matches on Subject: below --
2013-02-25 2:01 [PATCH V3 " Yan, Zheng
2013-02-25 2:01 ` [PATCH 4/7] perf, x86: Save/resotre LBR stack during context switch Yan, Zheng
2013-01-30 6:30 [PATCH 0/7] perf, x86: Haswell LBR call stack support Yan, Zheng
2013-01-30 6:30 ` [PATCH 4/7] perf, x86: Save/resotre LBR stack during context switch Yan, Zheng
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