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authorWaiman Long <longman@redhat.com>2019-04-04 20:43:19 +0300
committerIngo Molnar <mingo@kernel.org>2019-04-10 11:56:06 +0300
commita8654596f0371c2604c4d475422c48f4fc6a56c9 (patch)
tree6d021c1c7c2d39594ad5f080059920949afd8160 /arch/Kconfig
parentbf20616f46e536fe8affed6f138db4b3040b55a6 (diff)
downloadlinux-a8654596f0371c2604c4d475422c48f4fc6a56c9.tar.xz
locking/rwsem: Enable lock event counting
Add lock event counting calls so that we can track the number of lock events happening in the rwsem code. With CONFIG_LOCK_EVENT_COUNTS on and booting a 4-socket 112-thread x86-64 system, the rwsem counts after system bootup were as follows: rwsem_opt_fail=261 rwsem_opt_wlock=50636 rwsem_rlock=445 rwsem_rlock_fail=0 rwsem_rlock_fast=22 rwsem_rtrylock=810144 rwsem_sleep_reader=441 rwsem_sleep_writer=310 rwsem_wake_reader=355 rwsem_wake_writer=2335 rwsem_wlock=261 rwsem_wlock_fail=0 rwsem_wtrylock=20583 It can be seen that most of the lock acquisitions in the slowpath were write-locks in the optimistic spinning code path with no sleeping at all. For this system, over 97% of the locks are acquired via optimistic spinning. It illustrates the importance of optimistic spinning in improving the performance of rwsem. Signed-off-by: Waiman Long <longman@redhat.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Davidlohr Bueso <dbueso@suse.de> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Borislav Petkov <bp@alien8.de> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Tim Chen <tim.c.chen@linux.intel.com> Cc: Will Deacon <will.deacon@arm.com> Link: http://lkml.kernel.org/r/20190404174320.22416-11-longman@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/Kconfig')
-rw-r--r--arch/Kconfig1
1 files changed, 0 insertions, 1 deletions
diff --git a/arch/Kconfig b/arch/Kconfig
index 28c0f1ad80d7..02cb4e6a3e38 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -904,7 +904,6 @@ config ARCH_USE_MEMREMAP_PROT
config LOCK_EVENT_COUNTS
bool "Locking event counts collection"
depends on DEBUG_FS
- depends on QUEUED_SPINLOCKS
---help---
Enable light-weight counting of various locking related events
in the system with minimal performance impact. This reduces