aboutsummaryrefslogtreecommitdiff
path: root/lib
diff options
context:
space:
mode:
authorPeter Zijlstra <a.p.zijlstra@chello.nl>2007-07-19 01:48:56 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-07-19 10:04:49 -0700
commitf20786ff4da51e56b1956acf30be2552be266746 (patch)
treef6d0a9ed84ca476ca19fe7131d842699881756c4 /lib
parent8e18257d29238311e82085152741f0c3aa18b74d (diff)
downloadlinux-2.6.34-ux500-f20786ff4da51e56b1956acf30be2552be266746.tar.gz
lockstat: core infrastructure
Introduce the core lock statistics code. Lock statistics provides lock wait-time and hold-time (as well as the count of corresponding contention and acquisitions events). Also, the first few call-sites that encounter contention are tracked. Lock wait-time is the time spent waiting on the lock. This provides insight into the locking scheme, that is, a heavily contended lock is indicative of a too coarse locking scheme. Lock hold-time is the duration the lock was held, this provides a reference for the wait-time numbers, so they can be put into perspective. 1) lock 2) ... do stuff .. unlock 3) The time between 1 and 2 is the wait-time. The time between 2 and 3 is the hold-time. The lockdep held-lock tracking code is reused, because it already collects locks into meaningful groups (classes), and because it is an existing infrastructure for lock instrumentation. Currently lockdep tracks lock acquisition with two hooks: lock() lock_acquire() _lock() ... code protected by lock ... unlock() lock_release() _unlock() We need to extend this with two more hooks, in order to measure contention. lock_contended() - used to measure contention events lock_acquired() - completion of the contention These are then placed the following way: lock() lock_acquire() if (!_try_lock()) lock_contended() _lock() lock_acquired() ... do locked stuff ... unlock() lock_release() _unlock() (Note: the try_lock() 'trick' is used to avoid instrumenting all platform dependent lock primitive implementations.) It is also possible to toggle the two lockdep features at runtime using: /proc/sys/kernel/prove_locking /proc/sys/kernel/lock_stat (esp. turning off the O(n^2) prove_locking functionaliy can help) [akpm@linux-foundation.org: build fixes] [akpm@linux-foundation.org: nuke unneeded ifdefs] Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Ingo Molnar <mingo@elte.hu> Acked-by: Jason Baron <jbaron@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib')
-rw-r--r--lib/Kconfig.debug11
1 files changed, 11 insertions, 0 deletions
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 640844024ff..f3e0c2abcbd 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -283,6 +283,17 @@ config LOCKDEP
select KALLSYMS
select KALLSYMS_ALL
+config LOCK_STAT
+ bool "Lock usage statisitics"
+ depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
+ select LOCKDEP
+ select DEBUG_SPINLOCK
+ select DEBUG_MUTEXES
+ select DEBUG_LOCK_ALLOC
+ default n
+ help
+ This feature enables tracking lock contention points
+
config DEBUG_LOCKDEP
bool "Lock dependency engine debugging"
depends on DEBUG_KERNEL && LOCKDEP