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Subject[RFC] [Patch 4/4] lock contention tracking slimmed down
From
Date
This patch converts the lock statistics to a user of lib/statistic.c,
resulting in somewhat simpler code (a 300 lines-of-code diet).

Anyone interested in the details of code duplication might want to study:
- lock_time_inc() vs. statistic_add_util()
- lock_stats() vs. statistic_merge()
- clear_lock_stats() vs. statistic_reset()
- seq file code and per cpu data used by both approaches

The output has changed from a terribly wide table to an enormously
long list (just the generic way the statistics code prints data).
Still, all information has been retained:

<snip>
&rq->rq_lock_key contentions 0x34c04 545 task_rq_lock+0x64/0xb0
&rq->rq_lock_key contentions 0x34b62 148 double_rq_lock+0x4a/0x88
&rq->rq_lock_key contentions 0x357d0 8 double_lock_balance+0x7c/0x98
&rq->rq_lock_key contentions 0x35cf6 1 run_rebalance_domains+0x50a/0x5c0
&rq->rq_lock_key contentions other 404
&rq->rq_lock_key wait_read samples 0
&rq->rq_lock_key wait_read minimum 0
&rq->rq_lock_key wait_read average 0.000
&rq->rq_lock_key wait_read maximum 0
&rq->rq_lock_key wait_read variance 0.000
&rq->rq_lock_key wait_write samples 1106
&rq->rq_lock_key wait_write minimum 343
&rq->rq_lock_key wait_write average 361157.478
&rq->rq_lock_key wait_write maximum 5886625
&rq->rq_lock_key wait_write variance 753383636064.242
&rq->rq_lock_key hold_read samples 0
&rq->rq_lock_key hold_read minimum 0
&rq->rq_lock_key hold_read average 0.000
&rq->rq_lock_key hold_read maximum 0
&rq->rq_lock_key hold_read variance 0.000
&rq->rq_lock_key hold_write samples 551474
&rq->rq_lock_key hold_write minimum 94
&rq->rq_lock_key hold_write average 2517.107
&rq->rq_lock_key hold_write maximum 6269659
&rq->rq_lock_key hold_write variance 1996596045.121
xtime_lock contentions 0x17bd2 3327 account_ticks+0x96/0x184
xtime_lock contentions other 0
xtime_lock wait_read samples 0
xtime_lock wait_read minimum 0
xtime_lock wait_read average 0.000
xtime_lock wait_read maximum 0
xtime_lock wait_read variance 0.000
xtime_lock wait_write samples 3327
xtime_lock wait_write minimum 422
xtime_lock wait_write average 63371.777
xtime_lock wait_write maximum 3731202
xtime_lock wait_write variance 109560396493.412
xtime_lock hold_read samples 0
xtime_lock hold_read minimum 0
xtime_lock hold_read average 0.000
xtime_lock hold_read maximum 0
xtime_lock hold_read variance 0.000
xtime_lock hold_write samples 500405
xtime_lock hold_write minimum 203
xtime_lock hold_write average 2224.482
xtime_lock hold_write maximum 3495922
xtime_lock hold_write variance 350307599.860
clocksource_lock contentions other 0
clocksource_lock wait_read samples 0
clocksource_lock wait_read minimum 0
clocksource_lock wait_read average 0.000
clocksource_lock wait_read maximum 0
clocksource_lock wait_read variance 0.000
clocksource_lock wait_write samples 0
clocksource_lock wait_write minimum 0
clocksource_lock wait_write average 0.000
clocksource_lock wait_write maximum 0
clocksource_lock wait_write variance 0.000
clocksource_lock hold_read samples 0
clocksource_lock hold_read minimum 0
clocksource_lock hold_read average 0.000
clocksource_lock hold_read maximum 0
clocksource_lock hold_read variance 0.000
clocksource_lock hold_write samples 308908
clocksource_lock hold_write minimum 188
clocksource_lock hold_write average 435.165
clocksource_lock hold_write maximum 2485654
clocksource_lock hold_write variance 86184020.322
<snip>


Signed-off-by: Martin Peschke <mp3@de.ibm.com>
---
include/linux/lockdep.h | 35 ++---
kernel/lockdep.c | 122 ++-----------------
kernel/lockdep_proc.c | 294 +++++++-----------------------------------------
3 files changed, 76 insertions(+), 375 deletions(-)
Index: linux/kernel/lockdep.c
===================================================================
--- linux.orig/kernel/lockdep.c
+++ linux/kernel/lockdep.c
@@ -37,6 +37,7 @@
#include <linux/debug_locks.h>
#include <linux/irqflags.h>
#include <linux/utsname.h>
+#include <linux/statistic.h>

#include <asm/sections.h>

@@ -119,93 +120,9 @@ unsigned long nr_lock_classes;
static struct lock_class lock_classes[MAX_LOCKDEP_KEYS];

#ifdef CONFIG_LOCK_STAT
-static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS], lock_stats);
-
-static int lock_contention_point(struct lock_class *class, unsigned long ip)
-{
- int i;
-
- for (i = 0; i < ARRAY_SIZE(class->contention_point); i++) {
- if (class->contention_point[i] == 0) {
- class->contention_point[i] = ip;
- break;
- }
- if (class->contention_point[i] == ip)
- break;
- }
-
- return i;
-}
-
-static void lock_time_inc(struct lock_time *lt, s64 time)
-{
- if (time > lt->max)
- lt->max = time;
-
- if (time < lt->min || !lt->min)
- lt->min = time;
-
- lt->total += time;
- lt->nr++;
-}
-
-static inline void lock_time_add(struct lock_time *src, struct lock_time *dst)
-{
- dst->min += src->min;
- dst->max += src->max;
- dst->total += src->total;
- dst->nr += src->nr;
-}
-
-struct lock_class_stats lock_stats(struct lock_class *class)
-{
- struct lock_class_stats stats;
- int cpu, i;
-
- memset(&stats, 0, sizeof(struct lock_class_stats));
- for_each_possible_cpu(cpu) {
- struct lock_class_stats *pcs =
- &per_cpu(lock_stats, cpu)[class - lock_classes];
-
- for (i = 0; i < ARRAY_SIZE(stats.contention_point); i++)
- stats.contention_point[i] += pcs->contention_point[i];
-
- lock_time_add(&pcs->read_waittime, &stats.read_waittime);
- lock_time_add(&pcs->write_waittime, &stats.write_waittime);
-
- lock_time_add(&pcs->read_holdtime, &stats.read_holdtime);
- lock_time_add(&pcs->write_holdtime, &stats.write_holdtime);
- }
-
- return stats;
-}
-
-void clear_lock_stats(struct lock_class *class)
-{
- int cpu;
-
- for_each_possible_cpu(cpu) {
- struct lock_class_stats *cpu_stats =
- &per_cpu(lock_stats, cpu)[class - lock_classes];
-
- memset(cpu_stats, 0, sizeof(struct lock_class_stats));
- }
- memset(class->contention_point, 0, sizeof(class->contention_point));
-}
-
-static struct lock_class_stats *get_lock_stats(struct lock_class *class)
-{
- return &get_cpu_var(lock_stats)[class - lock_classes];
-}
-
-static void put_lock_stats(struct lock_class_stats *stats)
-{
- put_cpu_var(lock_stats);
-}
-
static void lock_release_holdtime(struct held_lock *hlock)
{
- struct lock_class_stats *stats;
+ struct statistic *stat = hlock->class->stat;
s64 holdtime;

if (!lock_stat)
@@ -213,12 +130,10 @@ static void lock_release_holdtime(struct

holdtime = sched_clock() - hlock->holdtime_stamp;

- stats = get_lock_stats(hlock->class);
if (hlock->read)
- lock_time_inc(&stats->read_holdtime, holdtime);
+ statistic_inc(stat, LOCK_STAT_HOLD_READ, holdtime);
else
- lock_time_inc(&stats->write_holdtime, holdtime);
- put_lock_stats(stats);
+ statistic_inc(stat, LOCK_STAT_HOLD_WRITE, holdtime);
}
#else
static inline void lock_release_holdtime(struct held_lock *hlock)
@@ -2745,9 +2660,8 @@ __lock_contended(struct lockdep_map *loc
{
struct task_struct *curr = current;
struct held_lock *hlock, *prev_hlock;
- struct lock_class_stats *stats;
unsigned int depth;
- int i, point;
+ int i;

depth = curr->lockdep_depth;
if (DEBUG_LOCKS_WARN_ON(!depth))
@@ -2761,22 +2675,15 @@ __lock_contended(struct lockdep_map *loc
*/
if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
break;
- if (hlock->instance == lock)
- goto found_it;
+ if (hlock->instance == lock) {
+ hlock->waittime_stamp = sched_clock();
+ _statistic_inc(hlock->class->stat, LOCK_STAT_CONT, ip);
+ return;
+ }
prev_hlock = hlock;
}
print_lock_contention_bug(curr, lock, ip);
return;
-
-found_it:
- hlock->waittime_stamp = sched_clock();
-
- point = lock_contention_point(hlock->class, ip);
-
- stats = get_lock_stats(hlock->class);
- if (point < ARRAY_SIZE(stats->contention_point))
- stats->contention_point[i]++;
- put_lock_stats(stats);
}

static void
@@ -2784,7 +2691,7 @@ __lock_acquired(struct lockdep_map *lock
{
struct task_struct *curr = current;
struct held_lock *hlock, *prev_hlock;
- struct lock_class_stats *stats;
+ struct statistic *stat;
unsigned int depth;
u64 now;
s64 waittime;
@@ -2817,12 +2724,11 @@ found_it:
waittime = now - hlock->waittime_stamp;
hlock->holdtime_stamp = now;

- stats = get_lock_stats(hlock->class);
+ stat = hlock->class->stat;
if (hlock->read)
- lock_time_inc(&stats->read_waittime, waittime);
+ _statistic_inc(stat, LOCK_STAT_WAIT_READ, waittime);
else
- lock_time_inc(&stats->write_waittime, waittime);
- put_lock_stats(stats);
+ _statistic_inc(stat, LOCK_STAT_WAIT_WRITE, waittime);
}

void lock_contended(struct lockdep_map *lock, unsigned long ip)
Index: linux/include/linux/lockdep.h
===================================================================
--- linux.orig/include/linux/lockdep.h
+++ linux/include/linux/lockdep.h
@@ -17,6 +17,7 @@ struct lockdep_map;
#include <linux/list.h>
#include <linux/debug_locks.h>
#include <linux/stacktrace.h>
+#include <linux/statistic.h>

/*
* Lock-class usage-state bits:
@@ -72,6 +73,17 @@ struct lock_class_key {
struct lockdep_subclass_key subkeys[MAX_LOCKDEP_SUBCLASSES];
};

+#ifdef CONFIG_LOCK_STAT
+enum lock_stat_enum {
+ LOCK_STAT_CONT,
+ LOCK_STAT_WAIT_READ,
+ LOCK_STAT_WAIT_WRITE,
+ LOCK_STAT_HOLD_READ,
+ LOCK_STAT_HOLD_WRITE,
+ _LOCK_STAT_NUMBER
+};
+#endif
+
/*
* The lock-class itself:
*/
@@ -117,30 +129,11 @@ struct lock_class {
int name_version;

#ifdef CONFIG_LOCK_STAT
- unsigned long contention_point[4];
+ struct statistic stat[_LOCK_STAT_NUMBER];
+ struct statistic_coll stat_coll;
#endif
};

-#ifdef CONFIG_LOCK_STAT
-struct lock_time {
- s64 min;
- s64 max;
- s64 total;
- unsigned long nr;
-};
-
-struct lock_class_stats {
- unsigned long contention_point[4];
- struct lock_time read_waittime;
- struct lock_time write_waittime;
- struct lock_time read_holdtime;
- struct lock_time write_holdtime;
-};
-
-struct lock_class_stats lock_stats(struct lock_class *class);
-void clear_lock_stats(struct lock_class *class);
-#endif
-
/*
* Map the lock object (the lock instance) to the lock-class object.
* This is embedded into specific lock instances:
Index: linux/kernel/lockdep_proc.c
===================================================================
--- linux.orig/kernel/lockdep_proc.c
+++ linux/kernel/lockdep_proc.c
@@ -349,260 +349,64 @@ static const struct file_operations proc
};

#ifdef CONFIG_LOCK_STAT
-
-struct lock_stat_data {
- struct lock_class *class;
- struct lock_class_stats stats;
-};
-
-struct lock_stat_seq {
- struct lock_stat_data *iter;
- struct lock_stat_data *iter_end;
- struct lock_stat_data stats[MAX_LOCKDEP_KEYS];
-};
-
-/*
- * sort on absolute number of contentions
- */
-int lock_stat_cmp(const void *l, const void *r)
-{
- const struct lock_stat_data *dl = l, *dr = r;
- unsigned long nl, nr;
-
- nl = dl->stats.read_waittime.nr + dl->stats.write_waittime.nr;
- nr = dr->stats.read_waittime.nr + dr->stats.write_waittime.nr;
-
- return nr - nl;
-}
-
-static void seq_line(struct seq_file *m, char c, int offset, int length)
-{
- int i;
-
- for (i = 0; i < offset; i++)
- seq_puts(m, " ");
- for (i = 0; i < length; i++)
- seq_printf(m, "%c", c);
- seq_puts(m, "\n");
-}
-
-static void snprint_time(char *buf, size_t bufsiz, s64 nr)
-{
- unsigned long rem;
-
- rem = do_div(nr, 1000); /* XXX: do_div_signed */
- snprintf(buf, bufsiz, "%lld.%02d", nr, ((int)rem+5)/10);
-}
-
-static void seq_time(struct seq_file *m, s64 time)
-{
- char num[15];
-
- snprint_time(num, sizeof(num), time);
- seq_printf(m, " %14s", num);
-}
-
-static void seq_lock_time(struct seq_file *m, struct lock_time *lt)
-{
- seq_printf(m, "%14lu", lt->nr);
- seq_time(m, lt->min);
- seq_time(m, lt->max);
- seq_time(m, lt->total);
-}
-
-static void seq_stats(struct seq_file *m, struct lock_stat_data *data)
-{
- char name[39];
- struct lock_class *class;
- struct lock_class_stats *stats;
- int i, namelen;
-
- class = data->class;
- stats = &data->stats;
-
- snprintf(name, 38, "%s", class->name);
- namelen = strlen(name);
-
- if (stats->write_holdtime.nr) {
- if (stats->read_holdtime.nr)
- seq_printf(m, "%38s-W:", name);
- else
- seq_printf(m, "%40s:", name);
-
- seq_lock_time(m, &stats->write_waittime);
- seq_puts(m, " ");
- seq_lock_time(m, &stats->write_holdtime);
- seq_puts(m, "\n");
- }
-
- if (stats->read_holdtime.nr) {
- seq_printf(m, "%38s-R:", name);
- seq_lock_time(m, &stats->read_waittime);
- seq_puts(m, " ");
- seq_lock_time(m, &stats->read_holdtime);
- seq_puts(m, "\n");
+struct statistic_info lock_stat_info[_LOCK_STAT_NUMBER] = {
+ [LOCK_STAT_CONT] = {
+ .name = "contentions",
+ .x_unit = "instruction_pointer",
+ .y_unit = "occurrence",
+ .defaults = "type=sparse entries=4",
+ .flags = STATISTIC_FLAGS_LABEL,
+ },
+ [LOCK_STAT_WAIT_READ] = {
+ .name = "wait_read",
+ .x_unit = "nanoseconds",
+ .y_unit = "occurrence",
+ .defaults = "type=utilisation",
+ },
+ [LOCK_STAT_WAIT_WRITE] = {
+ .name = "wait_write",
+ .x_unit = "nanoseconds",
+ .y_unit = "occurrence",
+ .defaults = "type=utilisation",
+ },
+ [LOCK_STAT_HOLD_READ] = {
+ .name = "hold_read",
+ .x_unit = "nanoseconds",
+ .y_unit = "occurrence",
+ .defaults = "type=utilisation",
+ },
+ [LOCK_STAT_HOLD_WRITE] = {
+ .name = "hold_write",
+ .x_unit = "nanoseconds",
+ .y_unit = "occurrence",
+ .defaults = "type=utilisation",
}
-
- if (stats->read_waittime.nr + stats->write_waittime.nr == 0)
- return;
-
- if (stats->read_holdtime.nr)
- namelen += 2;
-
- for (i = 0; i < ARRAY_SIZE(class->contention_point); i++) {
- char sym[KSYM_SYMBOL_LEN];
- char ip[32];
-
- if (class->contention_point[i] == 0)
- break;
-
- if (!i)
- seq_line(m, '-', 40-namelen, namelen);
-
- sprint_symbol(sym, class->contention_point[i]);
- snprintf(ip, sizeof(ip), "[<%p>]",
- (void *)class->contention_point[i]);
- seq_printf(m, "%40s %14lu %29s %s\n", name,
- stats->contention_point[i],
- ip, sym);
- }
- if (i) {
- seq_puts(m, "\n");
- seq_line(m, '.', 0, 40 + 1 + 8 * (14 + 1));
- seq_puts(m, "\n");
- }
-}
-
-static void seq_header(struct seq_file *m)
-{
- seq_printf(m, "lock_stat version 0.1\n");
- seq_line(m, '-', 0, 40 + 1 + 8 * (14 + 1));
- seq_printf(m, "%40s %14s %14s %14s %14s %14s %14s %14s %14s\n",
- "class name",
- "contentions",
- "waittime-min",
- "waittime-max",
- "waittime-total",
- "acquisitions",
- "holdtime-min",
- "holdtime-max",
- "holdtime-total");
- seq_line(m, '-', 0, 40 + 1 + 8 * (14 + 1));
- seq_printf(m, "\n");
-}
-
-static void *ls_start(struct seq_file *m, loff_t *pos)
-{
- struct lock_stat_seq *data = m->private;
-
- if (data->iter == data->stats)
- seq_header(m);
-
- return data->iter;
-}
-
-static void *ls_next(struct seq_file *m, void *v, loff_t *pos)
-{
- struct lock_stat_seq *data = m->private;
-
- (*pos)++;
-
- data->iter = v;
- data->iter++;
- if (data->iter == data->iter_end)
- data->iter = NULL;
-
- return data->iter;
-}
-
-static void ls_stop(struct seq_file *m, void *v)
-{
-}
-
-static int ls_show(struct seq_file *m, void *v)
-{
- struct lock_stat_seq *data = m->private;
-
- seq_stats(m, data->iter);
- return 0;
-}
-
-static struct seq_operations lockstat_ops = {
- .start = ls_start,
- .next = ls_next,
- .stop = ls_stop,
- .show = ls_show,
};

-static int lock_stat_open(struct inode *inode, struct file *file)
-{
- int res;
- struct lock_class *class;
- struct lock_stat_seq *data = vmalloc(sizeof(struct lock_stat_seq));
-
- if (!data)
- return -ENOMEM;
-
- res = seq_open(file, &lockstat_ops);
- if (!res) {
- struct lock_stat_data *iter = data->stats;
- struct seq_file *m = file->private_data;
-
- data->iter = iter;
- list_for_each_entry(class, &all_lock_classes, lock_entry) {
- iter->class = class;
- iter->stats = lock_stats(class);
- iter++;
- }
- data->iter_end = iter;
-
- sort(data->stats, data->iter_end - data->iter,
- sizeof(struct lock_stat_data),
- lock_stat_cmp, NULL);
-
- m->private = data;
- } else
- vfree(data);
+struct statistic_ui lock_stat_ui;

- return res;
+static void lock_stat_label(struct statistic_coll *coll, int i,
+ void *key, char *buf, int size)
+{
+ sprint_symbol(buf, *(unsigned long *)key);
}

-ssize_t lock_stat_write(struct file *file, const char __user *buf,
- size_t count, loff_t *ppos)
+static void lock_stat_init(void)
{
struct lock_class *class;
- char c;
-
- if (count) {
- if (get_user(c, buf))
- return -EFAULT;

- if (c != '0')
- return count;
-
- list_for_each_entry(class, &all_lock_classes, lock_entry)
- clear_lock_stats(class);
+ statistic_create(&lock_stat_ui, "lockstat");
+ list_for_each_entry(class, &all_lock_classes, lock_entry) {
+ class->stat_coll.stat = class->stat;
+ class->stat_coll.info = lock_stat_info;
+ class->stat_coll.number = _LOCK_STAT_NUMBER;
+ class->stat_coll.label = lock_stat_label;
+ strncpy(class->stat_coll.name, class->name,
+ STATISTIC_COLL_NAME_SIZE - 1);
+ statistic_attach(&class->stat_coll, &lock_stat_ui);
}
- return count;
-}
-
-static int lock_stat_release(struct inode *inode, struct file *file)
-{
- struct seq_file *seq = file->private_data;
-
- vfree(seq->private);
- seq->private = NULL;
- return seq_release(inode, file);
}
-
-static const struct file_operations proc_lock_stat_operations = {
- .open = lock_stat_open,
- .write = lock_stat_write,
- .read = seq_read,
- .llseek = seq_lseek,
- .release = lock_stat_release,
-};
-#endif /* CONFIG_LOCK_STAT */
+#endif

static int __init lockdep_proc_init(void)
{
@@ -617,9 +421,7 @@ static int __init lockdep_proc_init(void
entry->proc_fops = &proc_lockdep_stats_operations;

#ifdef CONFIG_LOCK_STAT
- entry = create_proc_entry("lock_stat", S_IRUSR, NULL);
- if (entry)
- entry->proc_fops = &proc_lock_stat_operations;
+ lock_stat_init();
#endif

return 0;

-
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