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authorTejun Heo <tj@kernel.org>2012-04-01 14:38:42 -0700
committerTejun Heo <tj@kernel.org>2012-04-01 14:38:42 -0700
commitedcb0722c654947908388df660791abd41e6617c (patch)
tree8c44dd4517bd562b58216dd01fb5abc42cb74a95 /block/blk-cgroup.c
parent2aa4a1523b40a065bc3a31e20097ea7a618ec3de (diff)
blkcg: introduce blkg_stat and blkg_rwstat
blkcg uses u64_stats_sync to avoid reading wrong u64 statistic values on 32bit archs and some stat counters have subtypes to distinguish read/writes and sync/async IOs. The stat code paths are confusing and involve a lot of going back and forth between blkcg core and specific policy implementations, and synchronization and subtype handling are open coded in blkcg core. This patch introduces struct blkg_stat and blkg_rwstat which, with accompanying operations, encapsulate stat updating and accessing with proper synchronization. blkg_stat is simple u64 counter with 64bit read-access protection. blkg_rwstat is the one with rw and [a]sync subcounters and takes @rw flags to distinguish IO subtypes (%REQ_WRITE and %REQ_SYNC) and replaces stat_sub_type indexed arrays. All counters in blkio_group_stats and blkio_group_stats_cpu are replaced with either blkg_stat or blkg_rwstat along with all users. This does add one u64_stats_sync per counter and increase stats_sync operations but they're empty/noops on 64bit archs and blkcg doesn't have too many counters, especially with DEBUG_BLK_CGROUP off. While the currently resulting code isn't necessarily simpler at the moment, this will enable further clean up of blkcg stats code. - BLKIO_STAT_{READ|WRITE|SYNC|ASYNC|TOTAL} renamed to BLKG_RWSTAT_{READ|WRITE|SYNC|ASYNC|TOTAL}. - blkg_stat_add() replaces blkio_add_stat() and blkio_check_and_dec_stat(). Note that BUG_ON() on underflow in the latter function no longer exists. It's *way* better to have underflowed stat counters than oopsing. - blkio_group_stats->dequeue is now a proper u64 stat counter instead of ulong. - reset_stats() updated to clear each stat counters individually and BLKG_STATS_DEBUG_CLEAR_{START|SIZE} are removed. - Some functions reconstruct rw flags from direction and sync booleans. This will be removed by future patches. Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'block/blk-cgroup.c')
-rw-r--r--block/blk-cgroup.c289
1 files changed, 127 insertions, 162 deletions
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 55ccbae6c434..09ac462ba89e 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -132,46 +132,6 @@ 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 queue_lock held.
- */
-static void blkio_add_stat(uint64_t *stat, uint64_t add, bool direction,
- bool sync)
-{
- if (direction)
- stat[BLKIO_STAT_WRITE] += add;
- else
- stat[BLKIO_STAT_READ] += add;
- if (sync)
- stat[BLKIO_STAT_SYNC] += add;
- else
- stat[BLKIO_STAT_ASYNC] += add;
-}
-
-/*
- * Decrements the appropriate stat variable if non-zero depending on the
- * request type. Panics on value being zero.
- * This should be called with the queue_lock held.
- */
-static void blkio_check_and_dec_stat(uint64_t *stat, bool direction, bool sync)
-{
- if (direction) {
- BUG_ON(stat[BLKIO_STAT_WRITE] == 0);
- stat[BLKIO_STAT_WRITE]--;
- } else {
- BUG_ON(stat[BLKIO_STAT_READ] == 0);
- stat[BLKIO_STAT_READ]--;
- }
- if (sync) {
- BUG_ON(stat[BLKIO_STAT_SYNC] == 0);
- stat[BLKIO_STAT_SYNC]--;
- } else {
- BUG_ON(stat[BLKIO_STAT_ASYNC] == 0);
- stat[BLKIO_STAT_ASYNC]--;
- }
-}
-
#ifdef CONFIG_DEBUG_BLK_CGROUP
/* This should be called with the queue_lock held. */
static void blkio_set_start_group_wait_time(struct blkio_group *blkg,
@@ -198,7 +158,8 @@ static void blkio_update_group_wait_time(struct blkio_group_stats *stats)
now = sched_clock();
if (time_after64(now, stats->start_group_wait_time))
- stats->group_wait_time += now - stats->start_group_wait_time;
+ blkg_stat_add(&stats->group_wait_time,
+ now - stats->start_group_wait_time);
blkio_clear_blkg_waiting(stats);
}
@@ -212,7 +173,8 @@ static void blkio_end_empty_time(struct blkio_group_stats *stats)
now = sched_clock();
if (time_after64(now, stats->start_empty_time))
- stats->empty_time += now - stats->start_empty_time;
+ blkg_stat_add(&stats->empty_time,
+ now - stats->start_empty_time);
blkio_clear_blkg_empty(stats);
}
@@ -239,11 +201,9 @@ void blkiocg_update_idle_time_stats(struct blkio_group *blkg,
if (blkio_blkg_idling(stats)) {
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);
- }
+ if (time_after64(now, stats->start_idle_time))
+ blkg_stat_add(&stats->idle_time,
+ now - stats->start_idle_time);
blkio_clear_blkg_idling(stats);
}
}
@@ -256,13 +216,10 @@ void blkiocg_update_avg_queue_size_stats(struct blkio_group *blkg,
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++;
+ blkg_stat_add(&stats->avg_queue_size_sum,
+ blkg_rwstat_sum(&stats->queued));
+ blkg_stat_add(&stats->avg_queue_size_samples, 1);
blkio_update_group_wait_time(stats);
- u64_stats_update_end(&stats->syncp);
}
EXPORT_SYMBOL_GPL(blkiocg_update_avg_queue_size_stats);
@@ -273,8 +230,7 @@ void blkiocg_set_start_empty_time(struct blkio_group *blkg,
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])
+ if (blkg_rwstat_sum(&stats->queued))
return;
/*
@@ -298,7 +254,7 @@ void blkiocg_update_dequeue_stats(struct blkio_group *blkg,
lockdep_assert_held(blkg->q->queue_lock);
- pd->stats.dequeue += dequeue;
+ blkg_stat_add(&pd->stats.dequeue, dequeue);
}
EXPORT_SYMBOL_GPL(blkiocg_update_dequeue_stats);
#else
@@ -314,14 +270,12 @@ void blkiocg_update_io_add_stats(struct blkio_group *blkg,
bool sync)
{
struct blkio_group_stats *stats = &blkg->pd[pol->plid]->stats;
+ int rw = (direction ? REQ_WRITE : 0) | (sync ? REQ_SYNC : 0);
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);
+ blkg_rwstat_add(&stats->queued, rw, 1);
blkio_end_empty_time(stats);
- u64_stats_update_end(&stats->syncp);
-
blkio_set_start_group_wait_time(blkg, pol, curr_blkg);
}
EXPORT_SYMBOL_GPL(blkiocg_update_io_add_stats);
@@ -331,13 +285,11 @@ void blkiocg_update_io_remove_stats(struct blkio_group *blkg,
bool direction, bool sync)
{
struct blkio_group_stats *stats = &blkg->pd[pol->plid]->stats;
+ int rw = (direction ? REQ_WRITE : 0) | (sync ? REQ_SYNC : 0);
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);
+ blkg_rwstat_add(&stats->queued, rw, -1);
}
EXPORT_SYMBOL_GPL(blkiocg_update_io_remove_stats);
@@ -350,12 +302,10 @@ void blkiocg_update_timeslice_used(struct blkio_group *blkg,
lockdep_assert_held(blkg->q->queue_lock);
- u64_stats_update_begin(&stats->syncp);
- stats->time += time;
+ blkg_stat_add(&stats->time, time);
#ifdef CONFIG_DEBUG_BLK_CGROUP
- stats->unaccounted_time += unaccounted_time;
+ blkg_stat_add(&stats->unaccounted_time, unaccounted_time);
#endif
- u64_stats_update_end(&stats->syncp);
}
EXPORT_SYMBOL_GPL(blkiocg_update_timeslice_used);
@@ -367,6 +317,7 @@ void blkiocg_update_dispatch_stats(struct blkio_group *blkg,
struct blkio_policy_type *pol,
uint64_t bytes, bool direction, bool sync)
{
+ int rw = (direction ? REQ_WRITE : 0) | (sync ? REQ_SYNC : 0);
struct blkg_policy_data *pd = blkg->pd[pol->plid];
struct blkio_group_stats_cpu *stats_cpu;
unsigned long flags;
@@ -384,13 +335,10 @@ void blkiocg_update_dispatch_stats(struct blkio_group *blkg,
stats_cpu = this_cpu_ptr(pd->stats_cpu);
- u64_stats_update_begin(&stats_cpu->syncp);
- stats_cpu->sectors += bytes >> 9;
- blkio_add_stat(stats_cpu->stat_arr_cpu[BLKIO_STAT_CPU_SERVICED],
- 1, direction, sync);
- blkio_add_stat(stats_cpu->stat_arr_cpu[BLKIO_STAT_CPU_SERVICE_BYTES],
- bytes, direction, sync);
- u64_stats_update_end(&stats_cpu->syncp);
+ blkg_stat_add(&stats_cpu->sectors, bytes >> 9);
+ blkg_rwstat_add(&stats_cpu->serviced, rw, 1);
+ blkg_rwstat_add(&stats_cpu->service_bytes, rw, bytes);
+
local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(blkiocg_update_dispatch_stats);
@@ -403,17 +351,15 @@ void blkiocg_update_completion_stats(struct blkio_group *blkg,
{
struct blkio_group_stats *stats = &blkg->pd[pol->plid]->stats;
unsigned long long now = sched_clock();
+ int rw = (direction ? REQ_WRITE : 0) | (sync ? REQ_SYNC : 0);
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);
+ blkg_rwstat_add(&stats->service_time, rw, now - io_start_time);
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);
- u64_stats_update_end(&stats->syncp);
+ blkg_rwstat_add(&stats->wait_time, rw,
+ io_start_time - start_time);
}
EXPORT_SYMBOL_GPL(blkiocg_update_completion_stats);
@@ -423,12 +369,11 @@ void blkiocg_update_io_merged_stats(struct blkio_group *blkg,
bool direction, bool sync)
{
struct blkio_group_stats *stats = &blkg->pd[pol->plid]->stats;
+ int rw = (direction ? REQ_WRITE : 0) | (sync ? REQ_SYNC : 0);
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);
- u64_stats_update_end(&stats->syncp);
+ blkg_rwstat_add(&stats->merged, rw, 1);
}
EXPORT_SYMBOL_GPL(blkiocg_update_io_merged_stats);
@@ -757,8 +702,9 @@ static void blkio_reset_stats_cpu(struct blkio_group *blkg, int plid)
struct blkio_group_stats_cpu *sc =
per_cpu_ptr(pd->stats_cpu, cpu);
- sc->sectors = 0;
- memset(sc->stat_arr_cpu, 0, sizeof(sc->stat_arr_cpu));
+ blkg_rwstat_reset(&sc->service_bytes);
+ blkg_rwstat_reset(&sc->serviced);
+ blkg_stat_reset(&sc->sectors);
}
}
@@ -768,7 +714,6 @@ blkiocg_reset_stats(struct cgroup *cgroup, struct cftype *cftype, u64 val)
struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
struct blkio_group *blkg;
struct hlist_node *n;
- int i;
spin_lock(&blkio_list_lock);
spin_lock_irq(&blkcg->lock);
@@ -786,14 +731,18 @@ blkiocg_reset_stats(struct cgroup *cgroup, struct cftype *cftype, u64 val)
struct blkio_group_stats *stats = &pd->stats;
/* queued stats shouldn't be cleared */
- for (i = 0; i < ARRAY_SIZE(stats->stat_arr); i++)
- if (i != BLKIO_STAT_QUEUED)
- memset(stats->stat_arr[i], 0,
- sizeof(stats->stat_arr[i]));
- stats->time = 0;
+ blkg_rwstat_reset(&stats->merged);
+ blkg_rwstat_reset(&stats->service_time);
+ blkg_rwstat_reset(&stats->wait_time);
+ blkg_stat_reset(&stats->time);
#ifdef CONFIG_DEBUG_BLK_CGROUP
- memset((void *)stats + BLKG_STATS_DEBUG_CLEAR_START, 0,
- BLKG_STATS_DEBUG_CLEAR_SIZE);
+ blkg_stat_reset(&stats->unaccounted_time);
+ blkg_stat_reset(&stats->avg_queue_size_sum);
+ blkg_stat_reset(&stats->avg_queue_size_samples);
+ blkg_stat_reset(&stats->dequeue);
+ blkg_stat_reset(&stats->group_wait_time);
+ blkg_stat_reset(&stats->idle_time);
+ blkg_stat_reset(&stats->empty_time);
#endif
blkio_reset_stats_cpu(blkg, pol->plid);
}
@@ -804,7 +753,7 @@ blkiocg_reset_stats(struct cgroup *cgroup, struct cftype *cftype, u64 val)
return 0;
}
-static void blkio_get_key_name(enum stat_sub_type type, const char *dname,
+static void blkio_get_key_name(enum blkg_rwstat_type type, const char *dname,
char *str, int chars_left, bool diskname_only)
{
snprintf(str, chars_left, "%s", dname);
@@ -817,19 +766,19 @@ static void blkio_get_key_name(enum stat_sub_type type, const char *dname,
if (diskname_only)
return;
switch (type) {
- case BLKIO_STAT_READ:
+ case BLKG_RWSTAT_READ:
strlcat(str, " Read", chars_left);
break;
- case BLKIO_STAT_WRITE:
+ case BLKG_RWSTAT_WRITE:
strlcat(str, " Write", chars_left);
break;
- case BLKIO_STAT_SYNC:
+ case BLKG_RWSTAT_SYNC:
strlcat(str, " Sync", chars_left);
break;
- case BLKIO_STAT_ASYNC:
+ case BLKG_RWSTAT_ASYNC:
strlcat(str, " Async", chars_left);
break;
- case BLKIO_STAT_TOTAL:
+ case BLKG_RWSTAT_TOTAL:
strlcat(str, " Total", chars_left);
break;
default:
@@ -838,29 +787,34 @@ static void blkio_get_key_name(enum stat_sub_type type, const char *dname,
}
static uint64_t blkio_read_stat_cpu(struct blkio_group *blkg, int plid,
- enum stat_type_cpu type, enum stat_sub_type sub_type)
+ enum stat_type_cpu type,
+ enum blkg_rwstat_type sub_type)
{
struct blkg_policy_data *pd = blkg->pd[plid];
+ u64 val = 0;
int cpu;
- struct blkio_group_stats_cpu *stats_cpu;
- u64 val = 0, tval;
if (pd->stats_cpu == NULL)
return val;
for_each_possible_cpu(cpu) {
- unsigned int start;
- stats_cpu = per_cpu_ptr(pd->stats_cpu, cpu);
-
- do {
- start = u64_stats_fetch_begin(&stats_cpu->syncp);
- if (type == BLKIO_STAT_CPU_SECTORS)
- tval = stats_cpu->sectors;
- else
- tval = stats_cpu->stat_arr_cpu[type][sub_type];
- } while(u64_stats_fetch_retry(&stats_cpu->syncp, start));
-
- val += tval;
+ struct blkio_group_stats_cpu *stats_cpu =
+ per_cpu_ptr(pd->stats_cpu, cpu);
+ struct blkg_rwstat rws;
+
+ switch (type) {
+ case BLKIO_STAT_CPU_SECTORS:
+ val += blkg_stat_read(&stats_cpu->sectors);
+ break;
+ case BLKIO_STAT_CPU_SERVICE_BYTES:
+ rws = blkg_rwstat_read(&stats_cpu->service_bytes);
+ val += rws.cnt[sub_type];
+ break;
+ case BLKIO_STAT_CPU_SERVICED:
+ rws = blkg_rwstat_read(&stats_cpu->serviced);
+ val += rws.cnt[sub_type];
+ break;
+ }
}
return val;
@@ -872,7 +826,7 @@ static uint64_t blkio_get_stat_cpu(struct blkio_group *blkg, int plid,
{
uint64_t disk_total, val;
char key_str[MAX_KEY_LEN];
- enum stat_sub_type sub_type;
+ enum blkg_rwstat_type sub_type;
if (type == BLKIO_STAT_CPU_SECTORS) {
val = blkio_read_stat_cpu(blkg, plid, type, 0);
@@ -881,7 +835,7 @@ static uint64_t blkio_get_stat_cpu(struct blkio_group *blkg, int plid,
return val;
}
- for (sub_type = BLKIO_STAT_READ; sub_type < BLKIO_STAT_TOTAL;
+ for (sub_type = BLKG_RWSTAT_READ; sub_type < BLKG_RWSTAT_NR;
sub_type++) {
blkio_get_key_name(sub_type, dname, key_str, MAX_KEY_LEN,
false);
@@ -889,10 +843,10 @@ static uint64_t blkio_get_stat_cpu(struct blkio_group *blkg, int plid,
cb->fill(cb, key_str, val);
}
- disk_total = blkio_read_stat_cpu(blkg, plid, type, BLKIO_STAT_READ) +
- blkio_read_stat_cpu(blkg, plid, type, BLKIO_STAT_WRITE);
+ disk_total = blkio_read_stat_cpu(blkg, plid, type, BLKG_RWSTAT_READ) +
+ blkio_read_stat_cpu(blkg, plid, type, BLKG_RWSTAT_WRITE);
- blkio_get_key_name(BLKIO_STAT_TOTAL, dname, key_str, MAX_KEY_LEN,
+ blkio_get_key_name(BLKG_RWSTAT_TOTAL, dname, key_str, MAX_KEY_LEN,
false);
cb->fill(cb, key_str, disk_total);
return disk_total;
@@ -905,65 +859,76 @@ 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;
+ struct blkg_rwstat rws = { };
int st;
if (type >= BLKIO_STAT_ARR_NR) {
- do {
- sync_start = u64_stats_fetch_begin(&stats->syncp);
- switch (type) {
- case BLKIO_STAT_TIME:
- v = stats->time;
- break;
+ switch (type) {
+ case BLKIO_STAT_TIME:
+ v = blkg_stat_read(&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 = blkg_stat_read(&stats->unaccounted_time);
+ break;
+ case BLKIO_STAT_AVG_QUEUE_SIZE: {
+ uint64_t samples;
- if (samples) {
- v = stats->avg_queue_size_sum;
- do_div(v, samples);
- }
- break;
+ samples = blkg_stat_read(&stats->avg_queue_size_samples);
+ if (samples) {
+ v = blkg_stat_read(&stats->avg_queue_size_sum);
+ do_div(v, samples);
}
- 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;
+ break;
+ }
+ case BLKIO_STAT_IDLE_TIME:
+ v = blkg_stat_read(&stats->idle_time);
+ break;
+ case BLKIO_STAT_EMPTY_TIME:
+ v = blkg_stat_read(&stats->empty_time);
+ break;
+ case BLKIO_STAT_DEQUEUE:
+ v = blkg_stat_read(&stats->dequeue);
+ break;
+ case BLKIO_STAT_GROUP_WAIT_TIME:
+ v = blkg_stat_read(&stats->group_wait_time);
+ break;
#endif
- default:
- WARN_ON_ONCE(1);
- }
- } while (u64_stats_fetch_retry(&stats->syncp, sync_start));
+ default:
+ WARN_ON_ONCE(1);
+ }
blkio_get_key_name(0, dname, key_str, MAX_KEY_LEN, true);
cb->fill(cb, key_str, v);
return v;
}
- for (st = BLKIO_STAT_READ; st < BLKIO_STAT_TOTAL; 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));
+ switch (type) {
+ case BLKIO_STAT_MERGED:
+ rws = blkg_rwstat_read(&stats->merged);
+ break;
+ case BLKIO_STAT_SERVICE_TIME:
+ rws = blkg_rwstat_read(&stats->service_time);
+ break;
+ case BLKIO_STAT_WAIT_TIME:
+ rws = blkg_rwstat_read(&stats->wait_time);
+ break;
+ case BLKIO_STAT_QUEUED:
+ rws = blkg_rwstat_read(&stats->queued);
+ break;
+ default:
+ WARN_ON_ONCE(true);
+ break;
+ }
+ for (st = BLKG_RWSTAT_READ; st < BLKG_RWSTAT_NR; st++) {
blkio_get_key_name(st, dname, key_str, MAX_KEY_LEN, false);
- cb->fill(cb, key_str, v);
- if (st == BLKIO_STAT_READ || st == BLKIO_STAT_WRITE)
- disk_total += v;
+ cb->fill(cb, key_str, rws.cnt[st]);
+ if (st == BLKG_RWSTAT_READ || st == BLKG_RWSTAT_WRITE)
+ disk_total += rws.cnt[st];
}
- blkio_get_key_name(BLKIO_STAT_TOTAL, dname, key_str, MAX_KEY_LEN,
+ blkio_get_key_name(BLKG_RWSTAT_TOTAL, dname, key_str, MAX_KEY_LEN,
false);
cb->fill(cb, key_str, disk_total);
return disk_total;