[PATCH 5/5] blkcg: remove blkio_group->stats_lock
From: Tejun Heo
Date: Thu Mar 08 2012 - 13:54:33 EST
With recent plug merge updates, all non-percpu stat updates happen
under queue_lock making stats_lock unnecessary to synchronize stat
updates. The only synchronization necessary is stat reading, which
can be done using u64_stats_sync instead.
This patch removes blkio_group->stats_lock and adds
blkio_group_stats->syncp for reader synchronization.
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Cc: Vivek Goyal <vgoyal@xxxxxxxxxx>
---
block/blk-cgroup.c | 209 +++++++++++++++++++++++++--------------------------
block/blk-cgroup.h | 3 +-
2 files changed, 103 insertions(+), 109 deletions(-)
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 80887bc..b15a517 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -156,7 +156,7 @@ static inline void blkio_update_group_iops(struct blkio_group *blkg,
/*
* Add to the appropriate stat variable depending on the request type.
- * This should be called with the blkg->stats_lock held.
+ * This should be called with queue_lock held.
*/
static void blkio_add_stat(uint64_t *stat, uint64_t add, bool direction,
bool sync)
@@ -174,7 +174,7 @@ static void blkio_add_stat(uint64_t *stat, uint64_t add, bool direction,
/*
* Decrements the appropriate stat variable if non-zero depending on the
* request type. Panics on value being zero.
- * This should be called with the blkg->stats_lock held.
+ * This should be called with the queue_lock held.
*/
static void blkio_check_and_dec_stat(uint64_t *stat, bool direction, bool sync)
{
@@ -195,7 +195,7 @@ static void blkio_check_and_dec_stat(uint64_t *stat, bool direction, bool sync)
}
#ifdef CONFIG_DEBUG_BLK_CGROUP
-/* This should be called with the blkg->stats_lock held. */
+/* This should be called with the queue_lock held. */
static void blkio_set_start_group_wait_time(struct blkio_group *blkg,
struct blkio_policy_type *pol,
struct blkio_group *curr_blkg)
@@ -210,7 +210,7 @@ static void blkio_set_start_group_wait_time(struct blkio_group *blkg,
blkio_mark_blkg_waiting(&pd->stats);
}
-/* This should be called with the blkg->stats_lock held. */
+/* This should be called with the queue_lock held. */
static void blkio_update_group_wait_time(struct blkio_group_stats *stats)
{
unsigned long long now;
@@ -224,7 +224,7 @@ static void blkio_update_group_wait_time(struct blkio_group_stats *stats)
blkio_clear_blkg_waiting(stats);
}
-/* This should be called with the blkg->stats_lock held. */
+/* This should be called with the queue_lock held. */
static void blkio_end_empty_time(struct blkio_group_stats *stats)
{
unsigned long long now;
@@ -241,84 +241,74 @@ static void blkio_end_empty_time(struct blkio_group_stats *stats)
void blkiocg_update_set_idle_time_stats(struct blkio_group *blkg,
struct blkio_policy_type *pol)
{
- struct blkg_policy_data *pd = blkg->pd[pol->plid];
- unsigned long flags;
+ struct blkio_group_stats *stats = &blkg->pd[pol->plid]->stats;
- spin_lock_irqsave(&blkg->stats_lock, flags);
- BUG_ON(blkio_blkg_idling(&pd->stats));
- pd->stats.start_idle_time = sched_clock();
- blkio_mark_blkg_idling(&pd->stats);
- spin_unlock_irqrestore(&blkg->stats_lock, flags);
+ lockdep_assert_held(blkg->q->queue_lock);
+ BUG_ON(blkio_blkg_idling(stats));
+
+ stats->start_idle_time = sched_clock();
+ blkio_mark_blkg_idling(stats);
}
EXPORT_SYMBOL_GPL(blkiocg_update_set_idle_time_stats);
void blkiocg_update_idle_time_stats(struct blkio_group *blkg,
struct blkio_policy_type *pol)
{
- struct blkg_policy_data *pd = blkg->pd[pol->plid];
- unsigned long flags;
- unsigned long long now;
- struct blkio_group_stats *stats;
+ struct blkio_group_stats *stats = &blkg->pd[pol->plid]->stats;
+
+ lockdep_assert_held(blkg->q->queue_lock);
- spin_lock_irqsave(&blkg->stats_lock, flags);
- stats = &pd->stats;
if (blkio_blkg_idling(stats)) {
- now = sched_clock();
- if (time_after64(now, stats->start_idle_time))
+ unsigned long long now = sched_clock();
+
+ if (time_after64(now, stats->start_idle_time)) {
+ u64_stats_update_begin(&stats->syncp);
stats->idle_time += now - stats->start_idle_time;
+ u64_stats_update_end(&stats->syncp);
+ }
blkio_clear_blkg_idling(stats);
}
- spin_unlock_irqrestore(&blkg->stats_lock, flags);
}
EXPORT_SYMBOL_GPL(blkiocg_update_idle_time_stats);
void blkiocg_update_avg_queue_size_stats(struct blkio_group *blkg,
struct blkio_policy_type *pol)
{
- struct blkg_policy_data *pd = blkg->pd[pol->plid];
- unsigned long flags;
- struct blkio_group_stats *stats;
+ struct blkio_group_stats *stats = &blkg->pd[pol->plid]->stats;
- spin_lock_irqsave(&blkg->stats_lock, flags);
- stats = &pd->stats;
+ lockdep_assert_held(blkg->q->queue_lock);
+
+ u64_stats_update_begin(&stats->syncp);
stats->avg_queue_size_sum +=
stats->stat_arr[BLKIO_STAT_QUEUED][BLKIO_STAT_READ] +
stats->stat_arr[BLKIO_STAT_QUEUED][BLKIO_STAT_WRITE];
stats->avg_queue_size_samples++;
blkio_update_group_wait_time(stats);
- spin_unlock_irqrestore(&blkg->stats_lock, flags);
+ u64_stats_update_end(&stats->syncp);
}
EXPORT_SYMBOL_GPL(blkiocg_update_avg_queue_size_stats);
void blkiocg_set_start_empty_time(struct blkio_group *blkg,
struct blkio_policy_type *pol)
{
- struct blkg_policy_data *pd = blkg->pd[pol->plid];
- unsigned long flags;
- struct blkio_group_stats *stats;
+ struct blkio_group_stats *stats = &blkg->pd[pol->plid]->stats;
- spin_lock_irqsave(&blkg->stats_lock, flags);
- stats = &pd->stats;
+ lockdep_assert_held(blkg->q->queue_lock);
if (stats->stat_arr[BLKIO_STAT_QUEUED][BLKIO_STAT_READ] ||
- stats->stat_arr[BLKIO_STAT_QUEUED][BLKIO_STAT_WRITE]) {
- spin_unlock_irqrestore(&blkg->stats_lock, flags);
+ stats->stat_arr[BLKIO_STAT_QUEUED][BLKIO_STAT_WRITE])
return;
- }
/*
* group is already marked empty. This can happen if cfqq got new
* request in parent group and moved to this group while being added
* to service tree. Just ignore the event and move on.
*/
- if(blkio_blkg_empty(stats)) {
- spin_unlock_irqrestore(&blkg->stats_lock, flags);
+ if (blkio_blkg_empty(stats))
return;
- }
stats->start_empty_time = sched_clock();
blkio_mark_blkg_empty(stats);
- spin_unlock_irqrestore(&blkg->stats_lock, flags);
}
EXPORT_SYMBOL_GPL(blkiocg_set_start_empty_time);
@@ -328,6 +318,8 @@ void blkiocg_update_dequeue_stats(struct blkio_group *blkg,
{
struct blkg_policy_data *pd = blkg->pd[pol->plid];
+ lockdep_assert_held(blkg->q->queue_lock);
+
pd->stats.dequeue += dequeue;
}
EXPORT_SYMBOL_GPL(blkiocg_update_dequeue_stats);
@@ -343,15 +335,16 @@ void blkiocg_update_io_add_stats(struct blkio_group *blkg,
struct blkio_group *curr_blkg, bool direction,
bool sync)
{
- struct blkg_policy_data *pd = blkg->pd[pol->plid];
- unsigned long flags;
+ struct blkio_group_stats *stats = &blkg->pd[pol->plid]->stats;
+
+ lockdep_assert_held(blkg->q->queue_lock);
+
+ u64_stats_update_begin(&stats->syncp);
+ blkio_add_stat(stats->stat_arr[BLKIO_STAT_QUEUED], 1, direction, sync);
+ blkio_end_empty_time(stats);
+ u64_stats_update_end(&stats->syncp);
- spin_lock_irqsave(&blkg->stats_lock, flags);
- blkio_add_stat(pd->stats.stat_arr[BLKIO_STAT_QUEUED], 1, direction,
- sync);
- blkio_end_empty_time(&pd->stats);
blkio_set_start_group_wait_time(blkg, pol, curr_blkg);
- spin_unlock_irqrestore(&blkg->stats_lock, flags);
}
EXPORT_SYMBOL_GPL(blkiocg_update_io_add_stats);
@@ -359,13 +352,14 @@ void blkiocg_update_io_remove_stats(struct blkio_group *blkg,
struct blkio_policy_type *pol,
bool direction, bool sync)
{
- struct blkg_policy_data *pd = blkg->pd[pol->plid];
- unsigned long flags;
+ struct blkio_group_stats *stats = &blkg->pd[pol->plid]->stats;
- spin_lock_irqsave(&blkg->stats_lock, flags);
- blkio_check_and_dec_stat(pd->stats.stat_arr[BLKIO_STAT_QUEUED],
- direction, sync);
- spin_unlock_irqrestore(&blkg->stats_lock, flags);
+ lockdep_assert_held(blkg->q->queue_lock);
+
+ u64_stats_update_begin(&stats->syncp);
+ blkio_check_and_dec_stat(stats->stat_arr[BLKIO_STAT_QUEUED], direction,
+ sync);
+ u64_stats_update_end(&stats->syncp);
}
EXPORT_SYMBOL_GPL(blkiocg_update_io_remove_stats);
@@ -374,15 +368,16 @@ void blkiocg_update_timeslice_used(struct blkio_group *blkg,
unsigned long time,
unsigned long unaccounted_time)
{
- struct blkg_policy_data *pd = blkg->pd[pol->plid];
- unsigned long flags;
+ struct blkio_group_stats *stats = &blkg->pd[pol->plid]->stats;
+
+ lockdep_assert_held(blkg->q->queue_lock);
- spin_lock_irqsave(&blkg->stats_lock, flags);
- pd->stats.time += time;
+ u64_stats_update_begin(&stats->syncp);
+ stats->time += time;
#ifdef CONFIG_DEBUG_BLK_CGROUP
- pd->stats.unaccounted_time += unaccounted_time;
+ stats->unaccounted_time += unaccounted_time;
#endif
- spin_unlock_irqrestore(&blkg->stats_lock, flags);
+ u64_stats_update_end(&stats->syncp);
}
EXPORT_SYMBOL_GPL(blkiocg_update_timeslice_used);
@@ -428,20 +423,19 @@ void blkiocg_update_completion_stats(struct blkio_group *blkg,
uint64_t io_start_time, bool direction,
bool sync)
{
- struct blkg_policy_data *pd = blkg->pd[pol->plid];
- struct blkio_group_stats *stats;
- unsigned long flags;
+ struct blkio_group_stats *stats = &blkg->pd[pol->plid]->stats;
unsigned long long now = sched_clock();
- spin_lock_irqsave(&blkg->stats_lock, flags);
- stats = &pd->stats;
+ lockdep_assert_held(blkg->q->queue_lock);
+
+ u64_stats_update_begin(&stats->syncp);
if (time_after64(now, io_start_time))
blkio_add_stat(stats->stat_arr[BLKIO_STAT_SERVICE_TIME],
now - io_start_time, direction, sync);
if (time_after64(io_start_time, start_time))
blkio_add_stat(stats->stat_arr[BLKIO_STAT_WAIT_TIME],
io_start_time - start_time, direction, sync);
- spin_unlock_irqrestore(&blkg->stats_lock, flags);
+ u64_stats_update_end(&stats->syncp);
}
EXPORT_SYMBOL_GPL(blkiocg_update_completion_stats);
@@ -450,14 +444,13 @@ void blkiocg_update_io_merged_stats(struct blkio_group *blkg,
struct blkio_policy_type *pol,
bool direction, bool sync)
{
- struct blkg_policy_data *pd = blkg->pd[pol->plid];
- struct blkio_group_stats *stats;
- unsigned long flags;
+ struct blkio_group_stats *stats = &blkg->pd[pol->plid]->stats;
- spin_lock_irqsave(&blkg->stats_lock, flags);
- stats = &pd->stats;
+ lockdep_assert_held(blkg->q->queue_lock);
+
+ u64_stats_update_begin(&stats->syncp);
blkio_add_stat(stats->stat_arr[BLKIO_STAT_MERGED], 1, direction, sync);
- spin_unlock_irqrestore(&blkg->stats_lock, flags);
+ u64_stats_update_end(&stats->syncp);
}
EXPORT_SYMBOL_GPL(blkiocg_update_io_merged_stats);
@@ -558,7 +551,6 @@ static struct blkio_group *blkg_alloc(struct blkio_cgroup *blkcg,
if (!blkg)
return NULL;
- spin_lock_init(&blkg->stats_lock);
blkg->q = q;
INIT_LIST_HEAD(&blkg->q_node);
INIT_LIST_HEAD(&blkg->alloc_node);
@@ -929,7 +921,6 @@ static uint64_t blkio_get_stat_cpu(struct blkio_group *blkg, int plid,
return disk_total;
}
-/* This should be called with blkg->stats_lock held */
static uint64_t blkio_get_stat(struct blkio_group *blkg, int plid,
struct cgroup_map_cb *cb, const char *dname,
enum stat_type type)
@@ -937,42 +928,46 @@ static uint64_t blkio_get_stat(struct blkio_group *blkg, int plid,
struct blkio_group_stats *stats = &blkg->pd[plid]->stats;
uint64_t v = 0, disk_total = 0;
char key_str[MAX_KEY_LEN];
+ unsigned int sync_start;
int st;
if (type >= BLKIO_STAT_ARR_NR) {
- switch (type) {
- case BLKIO_STAT_TIME:
- v = stats->time;
- break;
+ do {
+ sync_start = u64_stats_fetch_begin(&stats->syncp);
+ switch (type) {
+ case BLKIO_STAT_TIME:
+ v = stats->time;
+ break;
#ifdef CONFIG_DEBUG_BLK_CGROUP
- case BLKIO_STAT_UNACCOUNTED_TIME:
- v = stats->unaccounted_time;
- break;
- case BLKIO_STAT_AVG_QUEUE_SIZE: {
- uint64_t samples = stats->avg_queue_size_samples;
+ case BLKIO_STAT_UNACCOUNTED_TIME:
+ v = stats->unaccounted_time;
+ break;
+ case BLKIO_STAT_AVG_QUEUE_SIZE: {
+ uint64_t samples = stats->avg_queue_size_samples;
- if (samples) {
- v = stats->avg_queue_size_sum;
- do_div(v, samples);
+ if (samples) {
+ v = stats->avg_queue_size_sum;
+ do_div(v, samples);
+ }
+ break;
}
- break;
- }
- case BLKIO_STAT_IDLE_TIME:
- v = stats->idle_time;
- break;
- case BLKIO_STAT_EMPTY_TIME:
- v = stats->empty_time;
- break;
- case BLKIO_STAT_DEQUEUE:
- v = stats->dequeue;
- break;
- case BLKIO_STAT_GROUP_WAIT_TIME:
- v = stats->group_wait_time;
- break;
+ case BLKIO_STAT_IDLE_TIME:
+ v = stats->idle_time;
+ break;
+ case BLKIO_STAT_EMPTY_TIME:
+ v = stats->empty_time;
+ break;
+ case BLKIO_STAT_DEQUEUE:
+ v = stats->dequeue;
+ break;
+ case BLKIO_STAT_GROUP_WAIT_TIME:
+ v = stats->group_wait_time;
+ break;
#endif
- default:
- WARN_ON_ONCE(1);
- }
+ default:
+ WARN_ON_ONCE(1);
+ }
+ } while (u64_stats_fetch_retry(&stats->syncp, sync_start));
blkio_get_key_name(0, dname, key_str, MAX_KEY_LEN, true);
cb->fill(cb, key_str, v);
@@ -980,7 +975,10 @@ static uint64_t blkio_get_stat(struct blkio_group *blkg, int plid,
}
for (st = BLKIO_STAT_READ; st < BLKIO_STAT_TOTAL; st++) {
- v = stats->stat_arr[type][st];
+ do {
+ sync_start = u64_stats_fetch_begin(&stats->syncp);
+ v = stats->stat_arr[type][st];
+ } while (u64_stats_fetch_retry(&stats->syncp, sync_start));
blkio_get_key_name(st, dname, key_str, MAX_KEY_LEN, false);
cb->fill(cb, key_str, v);
@@ -1250,15 +1248,12 @@ static int blkio_read_blkg_stats(struct blkio_cgroup *blkcg,
if (!dname)
continue;
- if (pcpu) {
+ if (pcpu)
cgroup_total += blkio_get_stat_cpu(blkg, plid,
cb, dname, type);
- } else {
- spin_lock(&blkg->stats_lock);
+ else
cgroup_total += blkio_get_stat(blkg, plid,
cb, dname, type);
- spin_unlock(&blkg->stats_lock);
- }
}
if (show_total)
cb->fill(cb, "Total", cgroup_total);
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 8bdcf50..9df5ab0 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -119,6 +119,7 @@ struct blkio_cgroup {
};
struct blkio_group_stats {
+ struct u64_stats_sync syncp;
/* total disk time and nr sectors dispatched by this group */
uint64_t time;
uint64_t stat_arr[BLKIO_STAT_ARR_NR][BLKIO_STAT_TOTAL];
@@ -200,8 +201,6 @@ struct blkio_group {
/* reference count */
int refcnt;
- /* Need to serialize the stats in the case of reset/update */
- spinlock_t stats_lock;
struct blkg_policy_data *pd[BLKIO_NR_POLICIES];
/* List of blkg waiting for per cpu stats memory to be allocated */
--
1.7.7.3
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