diff options
| author | markj <markj@FreeBSD.org> | 2015-07-18 00:22:00 +0000 |
|---|---|---|
| committer | markj <markj@FreeBSD.org> | 2015-07-18 00:22:00 +0000 |
| commit | 90a3119284b43adced3a11a1f3bcd020c3630453 (patch) | |
| tree | 298c04314a37eabda9a60c929317ede1dd060c25 /sys/kern/kern_lockstat.c | |
| parent | e853fb249f0a2e510bb3c9a54cda60ba290e5777 (diff) | |
| download | FreeBSD-src-90a3119284b43adced3a11a1f3bcd020c3630453.zip FreeBSD-src-90a3119284b43adced3a11a1f3bcd020c3630453.tar.gz | |
Modify lockstat_nsecs() to just return unless lockstat probes are actually
enabled. The cost of a timecounter read can be quite significant, and the
problem became more apparent after r284297, since that change resulted in
a call to lockstat_nsecs() for each acquisition of an rwlock read lock.
PR: 201642
Reviewed by: avg
Tested by: Jason Unovitch
MFC after: 3 days
Differential Revision: https://reviews.freebsd.org/D3073
Diffstat (limited to 'sys/kern/kern_lockstat.c')
| -rw-r--r-- | sys/kern/kern_lockstat.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/sys/kern/kern_lockstat.c b/sys/kern/kern_lockstat.c index 1c77312..eb7e177 100644 --- a/sys/kern/kern_lockstat.c +++ b/sys/kern/kern_lockstat.c @@ -45,7 +45,7 @@ uint32_t lockstat_probemap[LS_NPROBES]; void (*lockstat_probe_func)(uint32_t, uintptr_t, uintptr_t, uintptr_t, uintptr_t, uintptr_t); - +int lockstat_enabled = 0; uint64_t lockstat_nsecs(void) @@ -53,6 +53,9 @@ lockstat_nsecs(void) struct bintime bt; uint64_t ns; + if (!lockstat_enabled) + return (0); + binuptime(&bt); ns = bt.sec * (uint64_t)1000000000; ns += ((uint64_t)1000000000 * (uint32_t)(bt.frac >> 32)) >> 32; |
