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Message-Id: <1386745860-21143-1-git-send-email-zheng.z.yan@intel.com>
Date: Wed, 11 Dec 2013 15:10:45 +0800
From: "Yan, Zheng" <zheng.z.yan@...el.com>
To: linux-kernel@...r.kernel.org
Cc: a.p.zijlstra@...llo.nl, eranian@...gle.com, andi@...stfloor.org,
"Yan, Zheng" <zheng.z.yan@...el.com>
Subject: [PATCH 00/15] perf, x86: Haswell LBR call stack support
From: "Yan, Zheng" <zheng.z.yan@...el.com>
Haswell has a new feature that utilizes the existing Last Branch Record
facility to record call chains. When the feature is enabled, function
call will be collected as normal, but as return instructions are executed
the last captured branch record is popped from the on-chip LBR registers.
The LBR call stack facility can help perf to get call chains of progam
without frame pointer. This feature can be disabled/enabled through an
attribute file in the cpu pmu sysfs directory.
The LBR call stack has following known limitations
- Zero length calls are not filtered out by hardware
- Exception handing such as setjmp/longjmp will have calls/returns not
match
- Pushing different return address onto the stack will have calls/returns
not match
- If callstack is deeper than the LBR, only the last entries are captured
Change since previous version
- split change into more patches
- introduce context switch callback and use it to flush LBR
- use the context switch callback to save/restore LBR
- dynamic allocate memory area for storing LBR stack, always switch the
memory area during context switch
- disable this feature by default
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