mtx: microoptimize lockstat handling in __mtx_lock_sleep
This saves a function call and multiple branches after the lock is acquired.
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7640beb920
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=313875
@ -62,7 +62,7 @@ SDT_PROBE_DEFINE1(lockstat, , , sx__downgrade, "struct sx *");
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SDT_PROBE_DEFINE2(lockstat, , , thread__spin, "struct mtx *", "uint64_t");
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int __read_mostly lockstat_enabled;
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volatile int __read_mostly lockstat_enabled;
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uint64_t
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lockstat_nsecs(struct lock_object *lo)
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@ -446,6 +446,7 @@ __mtx_lock_sleep(volatile uintptr_t *c, uintptr_t v, uintptr_t tid, int opts,
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u_int sleep_cnt = 0;
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int64_t sleep_time = 0;
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int64_t all_time = 0;
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int doing_lockstat;
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#endif
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if (SCHEDULER_STOPPED())
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@ -484,7 +485,9 @@ __mtx_lock_sleep(volatile uintptr_t *c, uintptr_t v, uintptr_t tid, int opts,
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"_mtx_lock_sleep: %s contested (lock=%p) at %s:%d",
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m->lock_object.lo_name, (void *)m->mtx_lock, file, line);
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#ifdef KDTRACE_HOOKS
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all_time -= lockstat_nsecs(&m->lock_object);
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doing_lockstat = lockstat_enabled;
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if (__predict_false(doing_lockstat))
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all_time -= lockstat_nsecs(&m->lock_object);
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#endif
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for (;;) {
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@ -591,15 +594,17 @@ __mtx_lock_sleep(volatile uintptr_t *c, uintptr_t v, uintptr_t tid, int opts,
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#endif
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v = MTX_READ_VALUE(m);
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}
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#ifdef KDTRACE_HOOKS
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all_time += lockstat_nsecs(&m->lock_object);
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#endif
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#ifdef KTR
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if (cont_logged) {
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CTR4(KTR_CONTENTION,
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"contention end: %s acquired by %p at %s:%d",
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m->lock_object.lo_name, (void *)tid, file, line);
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}
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#endif
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#ifdef KDTRACE_HOOKS
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if (__predict_true(!doing_lockstat))
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return;
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all_time += lockstat_nsecs(&m->lock_object);
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#endif
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LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(adaptive__acquire, m, contested,
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waittime, file, line);
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@ -68,7 +68,7 @@ SDT_PROBE_DECLARE(lockstat, , , thread__spin);
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#define LOCKSTAT_WRITER 0
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#define LOCKSTAT_READER 1
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extern int lockstat_enabled;
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extern volatile int lockstat_enabled;
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#ifdef KDTRACE_HOOKS
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