diff options
author | Waiman Long <longman@redhat.com> | 2019-04-04 20:43:17 +0300 |
---|---|---|
committer | Ingo Molnar <mingo@kernel.org> | 2019-04-10 11:56:04 +0300 |
commit | fb346fd9fc081c3d978c3f3d26d39334527a2662 (patch) | |
tree | 14c14e6b8c11ecaa8082fbcfa1cf302b98d45e45 /kernel/locking/qspinlock_stat.h | |
parent | ad53fa10fa9e816067bbae7109845940f5e6df50 (diff) | |
download | linux-fb346fd9fc081c3d978c3f3d26d39334527a2662.tar.xz |
locking/lock_events: Make lock_events available for all archs & other locks
The QUEUED_LOCK_STAT option to report queued spinlocks event counts
was previously allowed only on x86 architecture. To make the locking
event counting code more useful, it is now renamed to a more generic
LOCK_EVENT_COUNTS config option. This new option will be available to
all the architectures that use qspinlock at the moment.
Other locking code can now start to use the generic locking event
counting code by including lock_events.h and put the new locking event
names into the lock_events_list.h header file.
My experience with lock event counting is that it gives valuable insight
on how the locking code works and what can be done to make it better. I
would like to extend this benefit to other locking code like mutex and
rwsem in the near future.
The PV qspinlock specific code will stay in qspinlock_stat.h. The
locking event counters will now reside in the <debugfs>/lock_event_counts
directory.
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/20190404174320.22416-9-longman@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/locking/qspinlock_stat.h')
-rw-r--r-- | kernel/locking/qspinlock_stat.h | 141 |
1 files changed, 12 insertions, 129 deletions
diff --git a/kernel/locking/qspinlock_stat.h b/kernel/locking/qspinlock_stat.h index 1db5b375fcf4..54152670ff24 100644 --- a/kernel/locking/qspinlock_stat.h +++ b/kernel/locking/qspinlock_stat.h @@ -9,76 +9,29 @@ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * - * Authors: Waiman Long <waiman.long@hpe.com> + * Authors: Waiman Long <longman@redhat.com> */ -/* - * When queued spinlock statistical counters are enabled, the following - * debugfs files will be created for reporting the counter values: - * - * <debugfs>/qlockstat/ - * pv_hash_hops - average # of hops per hashing operation - * pv_kick_unlock - # of vCPU kicks issued at unlock time - * pv_kick_wake - # of vCPU kicks used for computing pv_latency_wake - * pv_latency_kick - average latency (ns) of vCPU kick operation - * pv_latency_wake - average latency (ns) from vCPU kick to wakeup - * pv_lock_stealing - # of lock stealing operations - * pv_spurious_wakeup - # of spurious wakeups in non-head vCPUs - * pv_wait_again - # of wait's after a queue head vCPU kick - * pv_wait_early - # of early vCPU wait's - * pv_wait_head - # of vCPU wait's at the queue head - * pv_wait_node - # of vCPU wait's at a non-head queue node - * lock_pending - # of locking operations via pending code - * lock_slowpath - # of locking operations via MCS lock queue - * lock_use_node2 - # of locking operations that use 2nd per-CPU node - * lock_use_node3 - # of locking operations that use 3rd per-CPU node - * lock_use_node4 - # of locking operations that use 4th per-CPU node - * lock_no_node - # of locking operations without using per-CPU node - * - * Subtracting lock_use_node[234] from lock_slowpath will give you - * lock_use_node1. - * - * Writing to the special ".reset_counts" file will reset all the above - * counter values. - * - * These statistical counters are implemented as per-cpu variables which are - * summed and computed whenever the corresponding debugfs files are read. This - * minimizes added overhead making the counters usable even in a production - * environment. - * - * There may be slight difference between pv_kick_wake and pv_kick_unlock. - */ #include "lock_events.h" -#ifdef CONFIG_QUEUED_LOCK_STAT +#ifdef CONFIG_LOCK_EVENT_COUNTS +#ifdef CONFIG_PARAVIRT_SPINLOCKS /* - * Collect pvqspinlock statistics + * Collect pvqspinlock locking event counts */ -#include <linux/debugfs.h> #include <linux/sched.h> #include <linux/sched/clock.h> #include <linux/fs.h> #define EVENT_COUNT(ev) lockevents[LOCKEVENT_ ## ev] -#undef LOCK_EVENT -#define LOCK_EVENT(name) [LOCKEVENT_ ## name] = #name, - -static const char * const lockevent_names[lockevent_num + 1] = { - -#include "lock_events_list.h" - - [LOCKEVENT_reset_cnts] = ".reset_counts", -}; - /* - * Per-cpu counters + * PV specific per-cpu counter */ -DEFINE_PER_CPU(unsigned long, lockevents[lockevent_num]); static DEFINE_PER_CPU(u64, pv_kick_time); /* - * Function to read and return the qlock statistical counter values + * Function to read and return the PV qspinlock counts. * * The following counters are handled specially: * 1. pv_latency_kick @@ -88,8 +41,8 @@ static DEFINE_PER_CPU(u64, pv_kick_time); * 3. pv_hash_hops * Average hops/hash = pv_hash_hops/pv_kick_unlock */ -static ssize_t lockevent_read(struct file *file, char __user *user_buf, - size_t count, loff_t *ppos) +ssize_t lockevent_read(struct file *file, char __user *user_buf, + size_t count, loff_t *ppos) { char buf[64]; int cpu, id, len; @@ -150,78 +103,6 @@ static ssize_t lockevent_read(struct file *file, char __user *user_buf, } /* - * Function to handle write request - * - * When id = .reset_cnts, reset all the counter values. - */ -static ssize_t lockevent_write(struct file *file, const char __user *user_buf, - size_t count, loff_t *ppos) -{ - int cpu; - - /* - * Get the counter ID stored in file->f_inode->i_private - */ - if ((long)file_inode(file)->i_private != LOCKEVENT_reset_cnts) - return count; - - for_each_possible_cpu(cpu) { - int i; - unsigned long *ptr = per_cpu_ptr(lockevents, cpu); - - for (i = 0 ; i < lockevent_num; i++) - WRITE_ONCE(ptr[i], 0); - } - return count; -} - -/* - * Debugfs data structures - */ -static const struct file_operations fops_lockevent = { - .read = lockevent_read, - .write = lockevent_write, - .llseek = default_llseek, -}; - -/* - * Initialize debugfs for the qspinlock statistical counters - */ -static int __init init_qspinlock_stat(void) -{ - struct dentry *d_counts = debugfs_create_dir("qlockstat", NULL); - int i; - - if (!d_counts) - goto out; - - /* - * Create the debugfs files - * - * As reading from and writing to the stat files can be slow, only - * root is allowed to do the read/write to limit impact to system - * performance. - */ - for (i = 0; i < lockevent_num; i++) - if (!debugfs_create_file(lockevent_names[i], 0400, d_counts, - (void *)(long)i, &fops_lockevent)) - goto fail_undo; - - if (!debugfs_create_file(lockevent_names[LOCKEVENT_reset_cnts], 0200, - d_counts, (void *)(long)LOCKEVENT_reset_cnts, - &fops_lockevent)) - goto fail_undo; - - return 0; -fail_undo: - debugfs_remove_recursive(d_counts); -out: - pr_warn("Could not create 'qlockstat' debugfs entries\n"); - return -ENOMEM; -} -fs_initcall(init_qspinlock_stat); - -/* * PV hash hop count */ static inline void lockevent_pv_hop(int hopcnt) @@ -260,8 +141,10 @@ static inline void __pv_wait(u8 *ptr, u8 val) #define pv_kick(c) __pv_kick(c) #define pv_wait(p, v) __pv_wait(p, v) -#else /* CONFIG_QUEUED_LOCK_STAT */ +#endif /* CONFIG_PARAVIRT_SPINLOCKS */ + +#else /* CONFIG_LOCK_EVENT_COUNTS */ static inline void lockevent_pv_hop(int hopcnt) { } -#endif /* CONFIG_QUEUED_LOCK_STAT */ +#endif /* CONFIG_LOCK_EVENT_COUNTS */ |