a8654596f0
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>
68 lines
3 KiB
C
68 lines
3 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* Authors: Waiman Long <longman@redhat.com>
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*/
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#ifndef LOCK_EVENT
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#define LOCK_EVENT(name) LOCKEVENT_ ## name,
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#endif
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#ifdef CONFIG_QUEUED_SPINLOCKS
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#ifdef CONFIG_PARAVIRT_SPINLOCKS
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/*
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* Locking events for PV qspinlock.
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*/
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LOCK_EVENT(pv_hash_hops) /* Average # of hops per hashing operation */
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LOCK_EVENT(pv_kick_unlock) /* # of vCPU kicks issued at unlock time */
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LOCK_EVENT(pv_kick_wake) /* # of vCPU kicks for pv_latency_wake */
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LOCK_EVENT(pv_latency_kick) /* Average latency (ns) of vCPU kick */
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LOCK_EVENT(pv_latency_wake) /* Average latency (ns) of kick-to-wakeup */
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LOCK_EVENT(pv_lock_stealing) /* # of lock stealing operations */
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LOCK_EVENT(pv_spurious_wakeup) /* # of spurious wakeups in non-head vCPUs */
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LOCK_EVENT(pv_wait_again) /* # of wait's after queue head vCPU kick */
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LOCK_EVENT(pv_wait_early) /* # of early vCPU wait's */
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LOCK_EVENT(pv_wait_head) /* # of vCPU wait's at the queue head */
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LOCK_EVENT(pv_wait_node) /* # of vCPU wait's at non-head queue node */
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#endif /* CONFIG_PARAVIRT_SPINLOCKS */
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/*
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* Locking events for qspinlock
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*
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* Subtracting lock_use_node[234] from lock_slowpath will give you
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* lock_use_node1.
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*/
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LOCK_EVENT(lock_pending) /* # of locking ops via pending code */
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LOCK_EVENT(lock_slowpath) /* # of locking ops via MCS lock queue */
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LOCK_EVENT(lock_use_node2) /* # of locking ops that use 2nd percpu node */
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LOCK_EVENT(lock_use_node3) /* # of locking ops that use 3rd percpu node */
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LOCK_EVENT(lock_use_node4) /* # of locking ops that use 4th percpu node */
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LOCK_EVENT(lock_no_node) /* # of locking ops w/o using percpu node */
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#endif /* CONFIG_QUEUED_SPINLOCKS */
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/*
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* Locking events for rwsem
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*/
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LOCK_EVENT(rwsem_sleep_reader) /* # of reader sleeps */
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LOCK_EVENT(rwsem_sleep_writer) /* # of writer sleeps */
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LOCK_EVENT(rwsem_wake_reader) /* # of reader wakeups */
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LOCK_EVENT(rwsem_wake_writer) /* # of writer wakeups */
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LOCK_EVENT(rwsem_opt_wlock) /* # of write locks opt-spin acquired */
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LOCK_EVENT(rwsem_opt_fail) /* # of failed opt-spinnings */
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LOCK_EVENT(rwsem_rlock) /* # of read locks acquired */
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LOCK_EVENT(rwsem_rlock_fast) /* # of fast read locks acquired */
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LOCK_EVENT(rwsem_rlock_fail) /* # of failed read lock acquisitions */
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LOCK_EVENT(rwsem_rtrylock) /* # of read trylock calls */
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LOCK_EVENT(rwsem_wlock) /* # of write locks acquired */
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LOCK_EVENT(rwsem_wlock_fail) /* # of failed write lock acquisitions */
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LOCK_EVENT(rwsem_wtrylock) /* # of write trylock calls */
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