svn commit: r285663 - in head/sys: cddl/dev/lockstat kern sys
Mark Johnston
markj at FreeBSD.org
Sat Jul 18 00:22:02 UTC 2015
Author: markj
Date: Sat Jul 18 00:22:00 2015
New Revision: 285663
URL: https://svnweb.freebsd.org/changeset/base/285663
Log:
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
Modified:
head/sys/cddl/dev/lockstat/lockstat.c
head/sys/kern/kern_lockstat.c
head/sys/sys/lockstat.h
Modified: head/sys/cddl/dev/lockstat/lockstat.c
==============================================================================
--- head/sys/cddl/dev/lockstat/lockstat.c Fri Jul 17 23:30:43 2015 (r285662)
+++ head/sys/cddl/dev/lockstat/lockstat.c Sat Jul 18 00:22:00 2015 (r285663)
@@ -159,6 +159,8 @@ lockstat_enable(void *arg, dtrace_id_t i
ASSERT(!lockstat_probemap[probe->lsp_probe]);
+ lockstat_enabled++;
+
lockstat_probemap[probe->lsp_probe] = id;
#ifdef DOODAD
membar_producer();
@@ -182,6 +184,8 @@ lockstat_disable(void *arg, dtrace_id_t
ASSERT(lockstat_probemap[probe->lsp_probe]);
+ lockstat_enabled--;
+
lockstat_probemap[probe->lsp_probe] = 0;
#ifdef DOODAD
lockstat_hot_patch();
Modified: head/sys/kern/kern_lockstat.c
==============================================================================
--- head/sys/kern/kern_lockstat.c Fri Jul 17 23:30:43 2015 (r285662)
+++ head/sys/kern/kern_lockstat.c Sat Jul 18 00:22:00 2015 (r285663)
@@ -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;
Modified: head/sys/sys/lockstat.h
==============================================================================
--- head/sys/sys/lockstat.h Fri Jul 17 23:30:43 2015 (r285662)
+++ head/sys/sys/lockstat.h Sat Jul 18 00:22:00 2015 (r285663)
@@ -154,6 +154,7 @@ typedef void (*lockstat_probe_func_t)(ui
uintptr_t arg2, uintptr_t arg3, uintptr_t arg4);
extern lockstat_probe_func_t lockstat_probe_func;
extern uint64_t lockstat_nsecs(void);
+extern int lockstat_enabled;
#ifdef KDTRACE_HOOKS
/*
More information about the svn-src-all
mailing list