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locking/qspinlock_stat: Introduce generic lockevent_*() counting APIs

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The percpu event counts used by qspinlock code can be useful for
other locking code as well. So a new set of lockevent_* counting APIs
is introduced with the lock event names extracted out into the new
lock_events_list.h header file for easier addition in the future.

The existing qstat_inc() calls are replaced by either lockevent_inc() or
lockevent_cond_inc() calls.

The qstat_hop() call is renamed to lockevent_pv_hop(). The "reset_counters"
debugfs file is also renamed to ".reset_counts".

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/20190404174320.22416-8-longman@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Waiman Long 2019-04-04 13:43:16 -04:00 committed by Ingo Molnar
parent 3b4ba6643d
commit ad53fa10fa
5 changed files with 181 additions and 114 deletions
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55
kernel/locking/lock_events.h Normal file
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@ -0,0 +1,55 @@
/* SPDX-License-Identifier: GPL-2.0 */
/*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* Authors: Waiman Long <longman@redhat.com>
*/
enum lock_events {
#include "lock_events_list.h"
lockevent_num, /* Total number of lock event counts */
LOCKEVENT_reset_cnts = lockevent_num,
};
#ifdef CONFIG_QUEUED_LOCK_STAT
/*
* Per-cpu counters
*/
DECLARE_PER_CPU(unsigned long, lockevents[lockevent_num]);
/*
* Increment the PV qspinlock statistical counters
*/
static inline void __lockevent_inc(enum lock_events event, bool cond)
{
if (cond)
__this_cpu_inc(lockevents[event]);
}
#define lockevent_inc(ev) __lockevent_inc(LOCKEVENT_ ##ev, true)
#define lockevent_cond_inc(ev, c) __lockevent_inc(LOCKEVENT_ ##ev, c)
static inline void __lockevent_add(enum lock_events event, int inc)
{
__this_cpu_add(lockevents[event], inc);
}
#define lockevent_add(ev, c) __lockevent_add(LOCKEVENT_ ##ev, c)
#else /* CONFIG_QUEUED_LOCK_STAT */
#define lockevent_inc(ev)
#define lockevent_add(ev, c)
#define lockevent_cond_inc(ev, c)
#endif /* CONFIG_QUEUED_LOCK_STAT */

50
kernel/locking/lock_events_list.h Normal file
View File

@ -0,0 +1,50 @@
/* SPDX-License-Identifier: GPL-2.0 */
/*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* Authors: Waiman Long <longman@redhat.com>
*/
#ifndef LOCK_EVENT
#define LOCK_EVENT(name) LOCKEVENT_ ## name,
#endif
#ifdef CONFIG_QUEUED_SPINLOCKS
#ifdef CONFIG_PARAVIRT_SPINLOCKS
/*
* Locking events for PV qspinlock.
*/
LOCK_EVENT(pv_hash_hops) /* Average # of hops per hashing operation */
LOCK_EVENT(pv_kick_unlock) /* # of vCPU kicks issued at unlock time */
LOCK_EVENT(pv_kick_wake) /* # of vCPU kicks for pv_latency_wake */
LOCK_EVENT(pv_latency_kick) /* Average latency (ns) of vCPU kick */
LOCK_EVENT(pv_latency_wake) /* Average latency (ns) of kick-to-wakeup */
LOCK_EVENT(pv_lock_stealing) /* # of lock stealing operations */
LOCK_EVENT(pv_spurious_wakeup) /* # of spurious wakeups in non-head vCPUs */
LOCK_EVENT(pv_wait_again) /* # of wait's after queue head vCPU kick */
LOCK_EVENT(pv_wait_early) /* # of early vCPU wait's */
LOCK_EVENT(pv_wait_head) /* # of vCPU wait's at the queue head */
LOCK_EVENT(pv_wait_node) /* # of vCPU wait's at non-head queue node */
#endif /* CONFIG_PARAVIRT_SPINLOCKS */
/*
* Locking events for qspinlock
*
* Subtracting lock_use_node[234] from lock_slowpath will give you
* lock_use_node1.
*/
LOCK_EVENT(lock_pending) /* # of locking ops via pending code */
LOCK_EVENT(lock_slowpath) /* # of locking ops via MCS lock queue */
LOCK_EVENT(lock_use_node2) /* # of locking ops that use 2nd percpu node */
LOCK_EVENT(lock_use_node3) /* # of locking ops that use 3rd percpu node */
LOCK_EVENT(lock_use_node4) /* # of locking ops that use 4th percpu node */
LOCK_EVENT(lock_no_node) /* # of locking ops w/o using percpu node */
#endif /* CONFIG_QUEUED_SPINLOCKS */

8
kernel/locking/qspinlock.c
View File

@ -395,7 +395,7 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val)
* 0,1,0 -> 0,0,1
*/
clear_pending_set_locked(lock);
qstat_inc(qstat_lock_pending, true);
lockevent_inc(lock_pending);
return;
/*
@ -403,7 +403,7 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val)
* queuing.
*/
queue:
qstat_inc(qstat_lock_slowpath, true);
lockevent_inc(lock_slowpath);
pv_queue:
node = this_cpu_ptr(&qnodes[0].mcs);
idx = node->count++;
@ -419,7 +419,7 @@ pv_queue:
* simple enough.
*/
if (unlikely(idx >= MAX_NODES)) {
qstat_inc(qstat_lock_no_node, true);
lockevent_inc(lock_no_node);
while (!queued_spin_trylock(lock))
cpu_relax();
goto release;
@ -430,7 +430,7 @@ pv_queue:
/*
* Keep counts of non-zero index values:
*/
qstat_inc(qstat_lock_use_node2 + idx - 1, idx);
lockevent_cond_inc(lock_use_node2 + idx - 1, idx);
/*
* Ensure that we increment the head node->count before initialising

19
kernel/locking/qspinlock_paravirt.h
View File

@ -89,7 +89,7 @@ static inline bool pv_hybrid_queued_unfair_trylock(struct qspinlock *lock)
if (!(val & _Q_LOCKED_PENDING_MASK) &&
(cmpxchg_acquire(&lock->locked, 0, _Q_LOCKED_VAL) == 0)) {
qstat_inc(qstat_pv_lock_stealing, true);
lockevent_inc(pv_lock_stealing);
return true;
}
if (!(val & _Q_TAIL_MASK) || (val & _Q_PENDING_MASK))
@ -219,7 +219,7 @@ static struct qspinlock **pv_hash(struct qspinlock *lock, struct pv_node *node)
hopcnt++;
if (!cmpxchg(&he->lock, NULL, lock)) {
WRITE_ONCE(he->node, node);
qstat_hop(hopcnt);
lockevent_pv_hop(hopcnt);
return &he->lock;
}
}
@ -320,8 +320,8 @@ static void pv_wait_node(struct mcs_spinlock *node, struct mcs_spinlock *prev)
smp_store_mb(pn->state, vcpu_halted);
if (!READ_ONCE(node->locked)) {
qstat_inc(qstat_pv_wait_node, true);
qstat_inc(qstat_pv_wait_early, wait_early);
lockevent_inc(pv_wait_node);
lockevent_cond_inc(pv_wait_early, wait_early);
pv_wait(&pn->state, vcpu_halted);
}
@ -339,7 +339,8 @@ static void pv_wait_node(struct mcs_spinlock *node, struct mcs_spinlock *prev)
* So it is better to spin for a while in the hope that the
* MCS lock will be released soon.
*/
qstat_inc(qstat_pv_spurious_wakeup, !READ_ONCE(node->locked));
lockevent_cond_inc(pv_spurious_wakeup,
!READ_ONCE(node->locked));
}
/*
@ -416,7 +417,7 @@ pv_wait_head_or_lock(struct qspinlock *lock, struct mcs_spinlock *node)
/*
* Tracking # of slowpath locking operations
*/
qstat_inc(qstat_lock_slowpath, true);
lockevent_inc(lock_slowpath);
for (;; waitcnt++) {
/*
@ -464,8 +465,8 @@ pv_wait_head_or_lock(struct qspinlock *lock, struct mcs_spinlock *node)
}
}
WRITE_ONCE(pn->state, vcpu_hashed);
qstat_inc(qstat_pv_wait_head, true);
qstat_inc(qstat_pv_wait_again, waitcnt);
lockevent_inc(pv_wait_head);
lockevent_cond_inc(pv_wait_again, waitcnt);
pv_wait(&lock->locked, _Q_SLOW_VAL);
/*
@ -528,7 +529,7 @@ __pv_queued_spin_unlock_slowpath(struct qspinlock *lock, u8 locked)
* vCPU is harmless other than the additional latency in completing
* the unlock.
*/
qstat_inc(qstat_pv_kick_unlock, true);
lockevent_inc(pv_kick_unlock);
pv_kick(node->cpu);
}

163
kernel/locking/qspinlock_stat.h
View File

@ -38,8 +38,8 @@
* Subtracting lock_use_node[234] from lock_slowpath will give you
* lock_use_node1.
*
* Writing to the "reset_counters" file will reset all the above counter
* values.
* 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
@ -48,27 +48,7 @@
*
* There may be slight difference between pv_kick_wake and pv_kick_unlock.
*/
enum qlock_stats {
qstat_pv_hash_hops,
qstat_pv_kick_unlock,
qstat_pv_kick_wake,
qstat_pv_latency_kick,
qstat_pv_latency_wake,
qstat_pv_lock_stealing,
qstat_pv_spurious_wakeup,
qstat_pv_wait_again,
qstat_pv_wait_early,
qstat_pv_wait_head,
qstat_pv_wait_node,
qstat_lock_pending,
qstat_lock_slowpath,
qstat_lock_use_node2,
qstat_lock_use_node3,
qstat_lock_use_node4,
qstat_lock_no_node,
qstat_num, /* Total number of statistical counters */
qstat_reset_cnts = qstat_num,
};
#include "lock_events.h"
#ifdef CONFIG_QUEUED_LOCK_STAT
/*
@ -79,99 +59,91 @@ enum qlock_stats {
#include <linux/sched/clock.h>
#include <linux/fs.h>
static const char * const qstat_names[qstat_num + 1] = {
[qstat_pv_hash_hops] = "pv_hash_hops",
[qstat_pv_kick_unlock] = "pv_kick_unlock",
[qstat_pv_kick_wake] = "pv_kick_wake",
[qstat_pv_spurious_wakeup] = "pv_spurious_wakeup",
[qstat_pv_latency_kick] = "pv_latency_kick",
[qstat_pv_latency_wake] = "pv_latency_wake",
[qstat_pv_lock_stealing] = "pv_lock_stealing",
[qstat_pv_wait_again] = "pv_wait_again",
[qstat_pv_wait_early] = "pv_wait_early",
[qstat_pv_wait_head] = "pv_wait_head",
[qstat_pv_wait_node] = "pv_wait_node",
[qstat_lock_pending] = "lock_pending",
[qstat_lock_slowpath] = "lock_slowpath",
[qstat_lock_use_node2] = "lock_use_node2",
[qstat_lock_use_node3] = "lock_use_node3",
[qstat_lock_use_node4] = "lock_use_node4",
[qstat_lock_no_node] = "lock_no_node",
[qstat_reset_cnts] = "reset_counters",
#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
*/
static DEFINE_PER_CPU(unsigned long, qstats[qstat_num]);
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
*
* The following counters are handled specially:
* 1. qstat_pv_latency_kick
* 1. pv_latency_kick
* Average kick latency (ns) = pv_latency_kick/pv_kick_unlock
* 2. qstat_pv_latency_wake
* 2. pv_latency_wake
* Average wake latency (ns) = pv_latency_wake/pv_kick_wake
* 3. qstat_pv_hash_hops
* 3. pv_hash_hops
* Average hops/hash = pv_hash_hops/pv_kick_unlock
*/
static ssize_t qstat_read(struct file *file, char __user *user_buf,
size_t count, loff_t *ppos)
static ssize_t lockevent_read(struct file *file, char __user *user_buf,
size_t count, loff_t *ppos)
{
char buf[64];
int cpu, counter, len;
u64 stat = 0, kicks = 0;
int cpu, id, len;
u64 sum = 0, kicks = 0;
/*
* Get the counter ID stored in file->f_inode->i_private
*/
counter = (long)file_inode(file)->i_private;
id = (long)file_inode(file)->i_private;
if (counter >= qstat_num)
if (id >= lockevent_num)
return -EBADF;
for_each_possible_cpu(cpu) {
stat += per_cpu(qstats[counter], cpu);
sum += per_cpu(lockevents[id], cpu);
/*
* Need to sum additional counter for some of them
* Need to sum additional counters for some of them
*/
switch (counter) {
switch (id) {
case qstat_pv_latency_kick:
case qstat_pv_hash_hops:
kicks += per_cpu(qstats[qstat_pv_kick_unlock], cpu);
case LOCKEVENT_pv_latency_kick:
case LOCKEVENT_pv_hash_hops:
kicks += per_cpu(EVENT_COUNT(pv_kick_unlock), cpu);
break;
case qstat_pv_latency_wake:
kicks += per_cpu(qstats[qstat_pv_kick_wake], cpu);
case LOCKEVENT_pv_latency_wake:
kicks += per_cpu(EVENT_COUNT(pv_kick_wake), cpu);
break;
}
}
if (counter == qstat_pv_hash_hops) {
if (id == LOCKEVENT_pv_hash_hops) {
u64 frac = 0;
if (kicks) {
frac = 100ULL * do_div(stat, kicks);
frac = 100ULL * do_div(sum, kicks);
frac = DIV_ROUND_CLOSEST_ULL(frac, kicks);
}
/*
* Return a X.XX decimal number
*/
len = snprintf(buf, sizeof(buf) - 1, "%llu.%02llu\n", stat, frac);
len = snprintf(buf, sizeof(buf) - 1, "%llu.%02llu\n",
sum, frac);
} else {
/*
* Round to the nearest ns
*/
if ((counter == qstat_pv_latency_kick) ||
(counter == qstat_pv_latency_wake)) {
if ((id == LOCKEVENT_pv_latency_kick) ||
(id == LOCKEVENT_pv_latency_wake)) {
if (kicks)
stat = DIV_ROUND_CLOSEST_ULL(stat, kicks);
sum = DIV_ROUND_CLOSEST_ULL(sum, kicks);
}
len = snprintf(buf, sizeof(buf) - 1, "%llu\n", stat);
len = snprintf(buf, sizeof(buf) - 1, "%llu\n", sum);
}
return simple_read_from_buffer(user_buf, count, ppos, buf, len);
@ -180,11 +152,9 @@ static ssize_t qstat_read(struct file *file, char __user *user_buf,
/*
* Function to handle write request
*
* When counter = reset_cnts, reset all the counter values.
* Since the counter updates aren't atomic, the resetting is done twice
* to make sure that the counters are very likely to be all cleared.
* When id = .reset_cnts, reset all the counter values.
*/
static ssize_t qstat_write(struct file *file, const char __user *user_buf,
static ssize_t lockevent_write(struct file *file, const char __user *user_buf,
size_t count, loff_t *ppos)
{
int cpu;
@ -192,14 +162,14 @@ static ssize_t qstat_write(struct file *file, const char __user *user_buf,
/*
* Get the counter ID stored in file->f_inode->i_private
*/
if ((long)file_inode(file)->i_private != qstat_reset_cnts)
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(qstats, cpu);
unsigned long *ptr = per_cpu_ptr(lockevents, cpu);
for (i = 0 ; i < qstat_num; i++)
for (i = 0 ; i < lockevent_num; i++)
WRITE_ONCE(ptr[i], 0);
}
return count;
@ -208,9 +178,9 @@ static ssize_t qstat_write(struct file *file, const char __user *user_buf,
/*
* Debugfs data structures
*/
static const struct file_operations fops_qstat = {
.read = qstat_read,
.write = qstat_write,
static const struct file_operations fops_lockevent = {
.read = lockevent_read,
.write = lockevent_write,
.llseek = default_llseek,
};
@ -219,10 +189,10 @@ static const struct file_operations fops_qstat = {
*/
static int __init init_qspinlock_stat(void)
{
struct dentry *d_qstat = debugfs_create_dir("qlockstat", NULL);
struct dentry *d_counts = debugfs_create_dir("qlockstat", NULL);
int i;
if (!d_qstat)
if (!d_counts)
goto out;
/*
@ -232,39 +202,31 @@ static int __init init_qspinlock_stat(void)
* root is allowed to do the read/write to limit impact to system
* performance.
*/
for (i = 0; i < qstat_num; i++)
if (!debugfs_create_file(qstat_names[i], 0400, d_qstat,
(void *)(long)i, &fops_qstat))
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(qstat_names[qstat_reset_cnts], 0200, d_qstat,
(void *)(long)qstat_reset_cnts, &fops_qstat))
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_qstat);
debugfs_remove_recursive(d_counts);
out:
pr_warn("Could not create 'qlockstat' debugfs entries\n");
return -ENOMEM;
}
fs_initcall(init_qspinlock_stat);
/*
* Increment the PV qspinlock statistical counters
*/
static inline void qstat_inc(enum qlock_stats stat, bool cond)
{
if (cond)
this_cpu_inc(qstats[stat]);
}
/*
* PV hash hop count
*/
static inline void qstat_hop(int hopcnt)
static inline void lockevent_pv_hop(int hopcnt)
{
this_cpu_add(qstats[qstat_pv_hash_hops], hopcnt);
this_cpu_add(EVENT_COUNT(pv_hash_hops), hopcnt);
}
/*
@ -276,7 +238,7 @@ static inline void __pv_kick(int cpu)
per_cpu(pv_kick_time, cpu) = start;
pv_kick(cpu);
this_cpu_add(qstats[qstat_pv_latency_kick], sched_clock() - start);
this_cpu_add(EVENT_COUNT(pv_latency_kick), sched_clock() - start);
}
/*
@ -289,9 +251,9 @@ static inline void __pv_wait(u8 *ptr, u8 val)
*pkick_time = 0;
pv_wait(ptr, val);
if (*pkick_time) {
this_cpu_add(qstats[qstat_pv_latency_wake],
this_cpu_add(EVENT_COUNT(pv_latency_wake),
sched_clock() - *pkick_time);
qstat_inc(qstat_pv_kick_wake, true);
lockevent_inc(pv_kick_wake);
}
}
@ -300,7 +262,6 @@ static inline void __pv_wait(u8 *ptr, u8 val)
#else /* CONFIG_QUEUED_LOCK_STAT */
static inline void qstat_inc(enum qlock_stats stat, bool cond) { }
static inline void qstat_hop(int hopcnt) { }
static inline void lockevent_pv_hop(int hopcnt) { }
#endif /* CONFIG_QUEUED_LOCK_STAT */