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| author | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2017-01-19 11:32:34 -0500 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2017-01-30 11:42:59 +0100 |
| commit | 4009f4b3a9d8b74547269f293e6a920adf278996 (patch) | |
| tree | d89abc6ec739d45d9f24a4684af2275ffa62fced /kernel/locking | |
| parent | bcc9a76d5ac426bc45c9e863b1830347827ca77a (diff) | |
| download | blackbird-op-linux-4009f4b3a9d8b74547269f293e6a920adf278996.tar.gz blackbird-op-linux-4009f4b3a9d8b74547269f293e6a920adf278996.zip | |
locking/rtmutex: Flip unlikely() branch to likely() in __rt_mutex_slowlock()
Running my likely/unlikely profiler for 3 weeks on two production
machines, I discovered that the unlikely() test in
__rt_mutex_slowlock() checking if state is TASK_INTERRUPTIBLE is hit
100% of the time, making it a very likely case.
The reason is, on a vanilla kernel, the majority case of calling
rt_mutex() is from the futex code. This code is always called as
TASK_INTERRUPTIBLE. In the -rt patch, this code is commonly called when
PREEMPT_RT is enabled with TASK_UNINTERRUPTIBLE. But that's not the
likely scenario.
The rt_mutex() code should be optimized for the common vanilla case,
and that is from a futex, with TASK_INTERRUPTIBLE as the state.
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170119113234.1efeedd1@gandalf.local.home
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/locking')
| -rw-r--r-- | kernel/locking/rtmutex.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c index 2f443ed2320a..d340be3a488f 100644 --- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -1179,7 +1179,7 @@ __rt_mutex_slowlock(struct rt_mutex *lock, int state, * TASK_INTERRUPTIBLE checks for signals and * timeout. Ignored otherwise. */ - if (unlikely(state == TASK_INTERRUPTIBLE)) { + if (likely(state == TASK_INTERRUPTIBLE)) { /* Signal pending? */ if (signal_pending(current)) ret = -EINTR; |
