From: Frederic Weisbecker Date: Sun, 5 Apr 2009 23:49:33 +0000 (+0200) Subject: tracing/lockdep: report the time waited for a lock X-Git-Tag: v2.6.31-rc1~401^2~184 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2062501ae6505dbc5bff3a792246c2661d114050;p=pandora-kernel.git tracing/lockdep: report the time waited for a lock While trying to optimize the new lock on reiserfs to replace the bkl, I find the lock tracing very useful though it lacks something important for performance (and latency) instrumentation: the time a task waits for a lock. That's what this patch implements: bash-4816 [000] 202.652815: lock_contended: lock_contended: &sb->s_type->i_mutex_key bash-4816 [000] 202.652819: lock_acquired: &rq->lock (0.000 us) <...>-4787 [000] 202.652825: lock_acquired: &rq->lock (0.000 us) <...>-4787 [000] 202.652829: lock_acquired: &rq->lock (0.000 us) bash-4816 [000] 202.652833: lock_acquired: &sb->s_type->i_mutex_key (16.005 us) As shown above, the "lock acquired" field is followed by the time it has been waiting for the lock. Usually, a lock contended entry is followed by a near lock_acquired entry with a non-zero time waited. Signed-off-by: Frederic Weisbecker Acked-by: Peter Zijlstra Cc: Steven Rostedt LKML-Reference: <1238975373-15739-1-git-send-email-fweisbec@gmail.com> Signed-off-by: Ingo Molnar --- Reading git-diff-tree failed