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[Bug nptl/4274] Performance issue: pthread_cond_signal() causes three context switches instead of one
- From: "jakub at redhat dot com" <sourceware-bugzilla at sourceware dot org>
- To: glibc-bugs at sources dot redhat dot com
- Date: 28 Mar 2007 08:17:51 -0000
- Subject: [Bug nptl/4274] Performance issue: pthread_cond_signal() causes three context switches instead of one
- References: <20070325101629.4274.bart.vanassche@gmail.com>
- Reply-to: sourceware-bugzilla at sourceware dot org
------- Additional Comments From jakub at redhat dot com 2007-03-28 09:17 -------
$ gcc -g -o /tmp/condvar-perf{,.c} -lpthread -std=gnu99 -lrt -O2 -m64 -W -Wall
$ /tmp/condvar-perf
NPTL
mutex elapsed: 6790 us; per iteration: 67 ns / 0 csw
c.v. ping-pong test elapsed: 1176092 us; per iteration: 11760 ns / 4 csw
signal ping-pong test elapsed: 727195 us; per iteration: 7271 ns / 4 csw
signal ping-pong no mtx elapsed: 971107 us; per iteration: 9711 ns / 4 csw
$ gcc -g -o /tmp/condvar-perf{,.c} -lpthread -std=gnu99 -lrt -O2 -m32 -W -Wall
$ /tmp/condvar-perf
NPTL
mutex elapsed: 7980 us; per iteration: 79 ns / 2e-05 csw
c.v. ping-pong test elapsed: 1328961 us; per iteration: 13289 ns / 4 csw
signal ping-pong test elapsed: 704607 us; per iteration: 7046 ns / 4 csw
signal ping-pong no mtx elapsed: 748424 us; per iteration: 7484 ns / 3.9 csw
$ /lib64/libc.so.6 | head -n 7; /lib/libc.so.6 | head -n 7; uname -a
GNU C Library stable release version 2.5, by Roland McGrath et al.
Copyright (C) 2006 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE.
Compiled by GNU CC version 4.1.1 20061011 (Red Hat 4.1.1-30).
Compiled on a Linux 2.6.9 system on 2007-01-05.
GNU C Library stable release version 2.5, by Roland McGrath et al.
Copyright (C) 2006 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE.
Compiled by GNU CC version 4.1.1 20061011 (Red Hat 4.1.1-30).
Compiled on a Linux 2.6.9 system on 2007-01-05.
Linux tucnak.ms.mff.cuni.cz 2.6.18-1.2869.fc6 #1 SMP Wed Dec 20 14:51:34 EST
2006 x86_64 x86_64 x86_64 GNU/Linux
--
http://sourceware.org/bugzilla/show_bug.cgi?id=4274
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