Author: mjg
Date: Fri Oct 20 03:32:42 2017
New Revision: 324787
URL: https://svnweb.freebsd.org/changeset/base/324787
Log:
rwlock: reduce lockstat branches in the slowpath
MFC after: 1 week
Modified:
head/sys/kern/kern_rwlock.c
Modified: head/sys/kern/kern_rwlock.c
==============================================================================
--- head/sys/kern/kern_rwlock.c Fri Oct 20 03:31:23 2017 (r324786)
+++ head/sys/kern/kern_rwlock.c Fri Oct 20 03:32:42 2017 (r324787)
@@ -847,6 +847,9 @@ __rw_wlock_hard(volatile uintptr_t *c, uintptr_t v, ui
int64_t sleep_time = 0;
int64_t all_time = 0;
#endif
+#if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING)
+ int doing_lockprof;
+#endif
if (SCHEDULER_STOPPED())
return;
@@ -875,10 +878,17 @@ __rw_wlock_hard(volatile uintptr_t *c, uintptr_t v, ui
CTR5(KTR_LOCK, "%s: %s contested (lock=%p) at %s:%d", __func__,
rw->lock_object.lo_name, (void *)rw->rw_lock, file, line);
-#ifdef KDTRACE_HOOKS
- all_time -= lockstat_nsecs(&rw->lock_object);
+#ifdef LOCK_PROFILING
+ doing_lockprof = 1;
state = v;
+#elif defined(KDTRACE_HOOKS)
+ doing_lockprof = lockstat_enabled;
+ if (__predict_false(doing_lockprof)) {
+ all_time -= lockstat_nsecs(&rw->lock_object);
+ state = v;
+ }
#endif
+
for (;;) {
if (v == RW_UNLOCKED) {
if (_rw_write_lock_fetch(rw, &v, tid))
@@ -1024,6 +1034,10 @@ __rw_wlock_hard(volatile uintptr_t *c, uintptr_t v, ui
#endif
v = RW_READ_VALUE(rw);
}
+#if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING)
+ if (__predict_true(!doing_lockprof))
+ return;
+#endif
#ifdef KDTRACE_HOOKS
all_time += lockstat_nsecs(&rw->lock_object);
if (sleep_time)
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