From 71a5964c110bea93ac926331547c25bdff67ce23 Mon Sep 17 00:00:00 2001 From: Ken Raeburn Date: Wed, 26 Aug 2009 23:30:59 +0100 Subject: [PATCH] Don't leave and reenter guile mode if mutex is available On Aug 5, 2009, at 10:06, Ken Raeburn wrote: > (1) In scm_pthread_mutex_lock, we leave and re-enter guile mode so > that we don't block the thread while in guile mode. But we could > use pthread_mutex_trylock first, and avoid the costs scm_leave_guile > seems to incur on the Mac. If we can't acquire the lock, it should > return immediately, and then we can do the expensive, blocking > version. A quick, hack version of this changed my run time for > A(3,8) from 17.5s to 14.5s, saving about 17%; sigaltstack and > sigprocmask are still in the picture, because they're called from > scm_catch_with_pre_unwind_handler. I'll work up a nicer patch > later. Ah, we already had scm_i_pthread_mutex_trylock lying around; that made things easy. A second timing test with A(3,9) and this version of the patch (based on 1.9.1) shows the same improvement. * libguile/threads.c (scm_pthread_mutex_lock): Try the mutex before leaving and reentering guile mode. --- libguile/threads.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/libguile/threads.c b/libguile/threads.c index 1721e0b28..e468f2fd5 100644 --- a/libguile/threads.c +++ b/libguile/threads.c @@ -1826,10 +1826,15 @@ scm_std_select (int nfds, int scm_pthread_mutex_lock (scm_i_pthread_mutex_t *mutex) { - scm_t_guile_ticket t = scm_leave_guile (); - int res = scm_i_pthread_mutex_lock (mutex); - scm_enter_guile (t); - return res; + if (scm_i_pthread_mutex_trylock (mutex) == 0) + return 0; + else + { + scm_t_guile_ticket t = scm_leave_guile (); + int res = scm_i_pthread_mutex_lock (mutex); + scm_enter_guile (t); + return res; + } } static void