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From: "mcree at orcon dot net dot nz" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sources.redhat.com
Subject: [Bug libc/12019] memchr overshoots on Alpha
Date: Thu, 23 Sep 2010 10:48:00 -0000 [thread overview]
Message-ID: <20100923104835.20548.qmail@sourceware.org> (raw)
In-Reply-To: <20100914154213.12019.eblake@redhat.com>
------- Additional Comments From mcree at orcon dot net dot nz 2010-09-23 10:48 -------
RTH's patch certainly fixes the segfault that was in the test case reported by
Debian. Speed tests also show it runs faster when searching large memory
buffers. I allocated 100Mbytes memory, filled it with 0xff except for a 0x00
half way in, then timed the memchr() search for the 0x00. With current memchr()
(alphaev6 optimised version from Debian's libc6.1-alphaev67 package) get (after
averaging over 10 memchr() searches):
cycles: 129525563 (scaled from 50.0%)
instructions: 50746044 (scaled from 50.0%)
cache-misses: 837238 (scaled from 50.0%)
mbox-replays: 4416463 (scaled from 25.0%)
With RTH's new version get (compiled with -O2 -mcpu=ev67):
cycles: 52405038 (scaled from 50.0%)
instructions: 62017822 (scaled from 50.0%)
cache-misses: 1034687 (scaled from 50.0%)
mbox-replays: 6866 (scaled from 25.0%)
so while it executes more CPU instructions it does it much faster! It's over
twice as fast as the old version. Nice. The almost complete removal of Mbox
replay traps is presumably a significant part of the speedup.
--
http://sourceware.org/bugzilla/show_bug.cgi?id=12019
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next prev parent reply other threads:[~2010-09-23 10:48 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-14 15:42 [Bug libc/12019] New: " eblake at redhat dot com
2010-09-14 15:43 ` [Bug libc/12019] " eblake at redhat dot com
2010-09-14 16:15 ` drepper at gmail dot com
2010-09-14 18:30 ` eblake at redhat dot com
2010-09-14 18:32 ` vapier at gentoo dot org
2010-09-14 18:32 ` vapier at gentoo dot org
2010-09-14 18:35 ` mattst88 at gmail dot com
2010-09-14 18:37 ` rth at gcc dot gnu dot org
2010-09-14 21:31 ` eblake at redhat dot com
2010-09-15 7:42 ` schwab at linux-m68k dot org
2010-09-15 8:06 ` bonzini at gnu dot org
2010-09-15 8:23 ` schwab at linux-m68k dot org
2010-09-15 8:27 ` schwab at linux-m68k dot org
2010-09-15 13:42 ` eblake at redhat dot com
2010-09-15 16:04 ` rth at gcc dot gnu dot org
2010-09-15 16:28 ` eblake at redhat dot com
2010-09-15 16:44 ` eblake at redhat dot com
2010-09-15 16:45 ` eblake at redhat dot com
2010-09-15 17:48 ` rth at gcc dot gnu dot org
2010-09-22 22:47 ` eblake at redhat dot com
2010-09-23 10:48 ` mcree at orcon dot net dot nz [this message]
2010-09-23 15:09 ` rth at gcc dot gnu dot org
2010-09-26 8:33 ` mcree at orcon dot net dot nz
2010-09-26 18:14 ` rth at gcc dot gnu dot org
[not found] <bug-12019-131@http.sourceware.org/bugzilla/>
2014-06-30 8:03 ` fweimer at redhat dot com
2023-12-11 17:21 ` gabravier at gmail dot com
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