From: Ingo Molnar <mingo@elte.hu>
Date: Mon, 23 Nov 2009 09:57:59 +0000 (+0100)
Subject: perf_events: Optimize the swcounter hotpath
X-Git-Tag: v2.6.33-rc1~399^2~106
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a4234bfcf4d72a10a99176cdef007345e9c3b4aa;p=pandora-kernel.git

perf_events: Optimize the swcounter hotpath

The structure init creates a bit memcpy, which shows
up big time in perf annotate output:

          :      ffffffff810a859d <__perf_sw_event>:
     1.68 :      ffffffff810a859d:       55                      push   %rbp
     1.69 :      ffffffff810a859e:       41 89 fa                mov    %edi,%r10d
     0.01 :      ffffffff810a85a1:       49 89 c9                mov    %rcx,%r9
     0.00 :      ffffffff810a85a4:       31 c0                   xor    %eax,%eax
     1.71 :      ffffffff810a85a6:       b9 16 00 00 00          mov    $0x16,%ecx
     0.00 :      ffffffff810a85ab:       48 89 e5                mov    %rsp,%rbp
     0.00 :      ffffffff810a85ae:       48 83 ec 60             sub    $0x60,%rsp
     1.52 :      ffffffff810a85b2:       48 8d 7d a0             lea    -0x60(%rbp),%rdi
    85.20 :      ffffffff810a85b6:       f3 ab                   rep stos %eax,%es:(%rdi)

None of the callees depends on the structure being pre-initialized,
so only initialize ->addr. This gets rid of the memcpy overhead.

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---

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