From: Li Zefan Date: Fri, 2 Jul 2010 03:07:32 +0000 (+0800) Subject: tracing: Allow to disable cmdline recording X-Git-Tag: v2.6.36-rc1~532^2~27^2~6 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e870e9a1240bcef1157ffaaf71dac63362e71904;p=pandora-kernel.git tracing: Allow to disable cmdline recording We found that even enabling a single trace event that will rarely be triggered can add big overhead to context switch. (lmbench context switch test) ------------------------------------------------- 2p/0K 2p/16K 2p/64K 8p/16K 8p/64K 16p/16K 16p/64K ctxsw ctxsw ctxsw ctxsw ctxsw ctxsw ctxsw ------ ------ ------ ------ ------ ------- ------- 2.19 2.3 2.21 2.56 2.13 2.54 2.07 2.39 2.51 2.35 2.75 2.27 2.81 2.24 The overhead is 6% ~ 11%. It's because when a trace event is enabled 3 tracepoints (sched_switch, sched_wakeup, sched_wakeup_new) will be activated to map pid to cmdname. We'd like to avoid this overhead, so add a trace option '(no)record-cmd' to allow to disable cmdline recording. Signed-off-by: Li Zefan LKML-Reference: <4C2D57F4.2050204@cn.fujitsu.com> Signed-off-by: Steven Rostedt --- Reading git-diff-tree failed