From: Andi Kleen <andi@firstfloor.org>
To: David Ahern <dsahern@gmail.com>
Cc: Andy Lutomirski <luto@amacapital.net>,
Andi Kleen <andi@firstfloor.org>,
Stephane Eranian <eranian@google.com>,
"Yan, Zheng" <zheng.z.yan@intel.com>,
LKML <linux-kernel@vger.kernel.org>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Ingo Molnar <mingo@kernel.org>,
Arnaldo Carvalho de Melo <acme@infradead.org>
Subject: Re: [PATCH v3 00/14] perf, x86: Haswell LBR call stack support
Date: Wed, 26 Feb 2014 21:53:22 +0100 [thread overview]
Message-ID: <20140226205322.GM22728@two.firstfloor.org> (raw)
In-Reply-To: <530E4B42.5090401@gmail.com>
> Is there some reason not to enable frame pointers?
It makes code slower.
Especially on Atom CPUs, where it causes pipeline stalls, but
also to some degree on others, because you lose one register and
spend a little bit of time setting it up, so making small
functions more expensive.
Another issue is that you can't enable it on a lot of existing
libraries, sometimes not even with a recompile. For example
glibc assembler functions do not support it at all, which
is a very common case.
They are designed to use dwarf, but in practice dwarf
is very slow (perf has to save the stack for every sample)
and in practice doesn't always work (too small stack saving,
wrong annotations, out of date or broken dwarf library etc.)
LBR callstack mode is not perfect either, and it has
its own tradeoffs, but in many cases it seems to be a good
and more efficient replacement for dwarf, when FP is not available.
-Andi
next prev parent reply other threads:[~2014-02-26 20:53 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-18 6:07 [PATCH v3 00/14] perf, x86: Haswell LBR call stack support Yan, Zheng
2014-02-18 6:07 ` [PATCH v3 01/14] perf, x86: Reduce lbr_sel_map size Yan, Zheng
2014-02-18 6:07 ` [PATCH v3 02/14] perf, core: introduce pmu context switch callback Yan, Zheng
2014-02-18 6:07 ` [PATCH v3 03/14] perf, x86: use context switch callback to flush LBR stack Yan, Zheng
2014-02-18 6:07 ` [PATCH v3 04/14] perf, x86: Basic Haswell LBR call stack support Yan, Zheng
2014-02-18 6:07 ` [PATCH v3 05/14] perf, core: pmu specific data for perf task context Yan, Zheng
2014-02-18 6:07 ` [PATCH v3 06/14] perf, core: always switch pmu specific data during context switch Yan, Zheng
2014-02-18 6:07 ` [PATCH v3 07/14] perf, x86: track number of events that use LBR callstack Yan, Zheng
2014-02-18 6:07 ` [PATCH v3 08/14] perf, x86: allocate space for storing LBR stack Yan, Zheng
2014-02-18 6:07 ` [PATCH v3 09/14] perf, x86: Save/resotre LBR stack during context switch Yan, Zheng
2014-02-18 6:07 ` [PATCH v3 10/14] perf, core: simplify need branch stack check Yan, Zheng
2014-02-18 6:07 ` [PATCH v3 11/14] perf, core: Pass perf_sample_data to perf_callchain() Yan, Zheng
2014-02-18 6:07 ` [PATCH v3 12/14] perf, x86: use LBR call stack to get user callchain Yan, Zheng
2014-02-18 6:07 ` [PATCH v3 13/14] perf, x86: enable LBR callstack when recording callchain Yan, Zheng
2014-02-18 6:07 ` [PATCH v3 14/14] perf, x86: Discard zero length call entries in LBR call stack Yan, Zheng
2014-02-23 19:47 ` [PATCH v3 00/14] perf, x86: Haswell LBR call stack support Stephane Eranian
2014-02-24 1:07 ` Yan, Zheng
2014-02-24 7:14 ` Peter Zijlstra
2014-02-26 2:39 ` Andy Lutomirski
2014-02-26 7:04 ` Stephane Eranian
2014-02-26 8:57 ` Yan, Zheng
2014-02-26 16:03 ` Andy Lutomirski
2014-02-26 18:55 ` Andi Kleen
2014-02-26 18:59 ` Andy Lutomirski
2014-02-26 19:19 ` David Ahern
2014-02-26 19:25 ` Andy Lutomirski
2014-02-26 20:14 ` David Ahern
2014-02-26 20:26 ` Andy Lutomirski
2014-04-09 11:48 ` Peter Zijlstra
2014-04-09 16:48 ` Andi Kleen
2014-04-09 17:40 ` Andi Kleen
2014-02-26 20:32 ` Peter Zijlstra
2014-02-26 20:53 ` Andi Kleen [this message]
2014-02-26 21:15 ` Peter Zijlstra
2014-02-26 21:33 ` Andi Kleen
2014-02-26 21:34 ` David Ahern
2014-02-26 21:42 ` Andi Kleen
2014-02-27 9:09 ` Stephane Eranian
2014-02-27 12:35 ` Ingo Molnar
2014-02-27 16:08 ` Andi Kleen
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