From 2062501ae6505dbc5bff3a792246c2661d114050 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Mon, 6 Apr 2009 01:49:33 +0200 Subject: [PATCH] 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 --- include/trace/lockdep_event_types.h | 23 ++++++++++++++++++----- kernel/lockdep.c | 8 ++++---- 2 files changed, 22 insertions(+), 9 deletions(-) diff --git a/include/trace/lockdep_event_types.h b/include/trace/lockdep_event_types.h index adccfcd2ec8f..863f1e4583a6 100644 --- a/include/trace/lockdep_event_types.h +++ b/include/trace/lockdep_event_types.h @@ -32,11 +32,24 @@ TRACE_FORMAT(lock_contended, TP_FMT("%s", lock->name) ); -TRACE_FORMAT(lock_acquired, - TP_PROTO(struct lockdep_map *lock, unsigned long ip), - TP_ARGS(lock, ip), - TP_FMT("%s", lock->name) - ); +TRACE_EVENT(lock_acquired, + TP_PROTO(struct lockdep_map *lock, unsigned long ip, s64 waittime), + + TP_ARGS(lock, ip, waittime), + + TP_STRUCT__entry( + __field(const char *, name) + __field(unsigned long, wait_usec) + __field(unsigned long, wait_nsec_rem) + ), + TP_fast_assign( + __entry->name = lock->name; + __entry->wait_nsec_rem = do_div(waittime, NSEC_PER_USEC); + __entry->wait_usec = (unsigned long) waittime; + ), + TP_printk("%s (%lu.%03lu us)", __entry->name, __entry->wait_usec, + __entry->wait_nsec_rem) +); #endif #endif diff --git a/kernel/lockdep.c b/kernel/lockdep.c index b0f011866969..c4582a6ea953 100644 --- a/kernel/lockdep.c +++ b/kernel/lockdep.c @@ -3061,6 +3061,8 @@ __lock_contended(struct lockdep_map *lock, unsigned long ip) put_lock_stats(stats); } +DEFINE_TRACE(lock_acquired); + static void __lock_acquired(struct lockdep_map *lock, unsigned long ip) { @@ -3099,6 +3101,8 @@ __lock_acquired(struct lockdep_map *lock, unsigned long ip) hlock->holdtime_stamp = now; } + trace_lock_acquired(lock, ip, waittime); + stats = get_lock_stats(hlock_class(hlock)); if (waittime) { if (hlock->read) @@ -3137,14 +3141,10 @@ void lock_contended(struct lockdep_map *lock, unsigned long ip) } EXPORT_SYMBOL_GPL(lock_contended); -DEFINE_TRACE(lock_acquired); - void lock_acquired(struct lockdep_map *lock, unsigned long ip) { unsigned long flags; - trace_lock_acquired(lock, ip); - if (unlikely(!lock_stat)) return; -- GitLab