From 124b4ebc8a293e616cc0a7eaba3587c9b7ff13ec Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Wed, 30 Mar 2011 08:58:25 -0400 Subject: [PATCH] cheap special-case optimization for normal mutexes cycle-level benchmark on atom cpu showed typical pthread_mutex_lock call dropping from ~120 cycles to ~90 cycles with this change. benefit may vary with compiler options and version, but this optimization is very cheap to make and should always help some. --- src/thread/pthread_mutex_lock.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/src/thread/pthread_mutex_lock.c b/src/thread/pthread_mutex_lock.c index 477b3d80..87b19752 100644 --- a/src/thread/pthread_mutex_lock.c +++ b/src/thread/pthread_mutex_lock.c @@ -3,6 +3,10 @@ int pthread_mutex_lock(pthread_mutex_t *m) { int r; + + if (m->_m_type == PTHREAD_MUTEX_NORMAL && !a_swap(&m->_m_lock, 1)) + return 0; + while ((r=pthread_mutex_trylock(m)) == EBUSY) { if (!(r=m->_m_lock) || (r&0x40000000)) continue; if ((m->_m_type&3) == PTHREAD_MUTEX_ERRORCHECK -- 2.25.1