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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.h
parent2aa4a1523b40a065bc3a31e20097ea7a618ec3de (diff)
downloadlinux-edcb0722c654947908388df660791abd41e6617c.tar.bz2
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.h')
-rw-r--r--block/blk-cgroup.h211
1 files changed, 166 insertions, 45 deletions
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 2060d812ae8e..7578df3938b4 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -69,12 +69,14 @@ enum stat_type_cpu {
#define BLKIO_STAT_CPU_ARR_NR (BLKIO_STAT_CPU_SERVICED + 1)
-enum stat_sub_type {
- BLKIO_STAT_READ = 0,
- BLKIO_STAT_WRITE,
- BLKIO_STAT_SYNC,
- BLKIO_STAT_ASYNC,
- BLKIO_STAT_TOTAL
+enum blkg_rwstat_type {
+ BLKG_RWSTAT_READ,
+ BLKG_RWSTAT_WRITE,
+ BLKG_RWSTAT_SYNC,
+ BLKG_RWSTAT_ASYNC,
+
+ BLKG_RWSTAT_NR,
+ BLKG_RWSTAT_TOTAL = BLKG_RWSTAT_NR,
};
/* blkg state flags */
@@ -124,54 +126,58 @@ struct blkio_cgroup {
uint64_t id;
};
+struct blkg_stat {
+ struct u64_stats_sync syncp;
+ uint64_t cnt;
+};
+
+struct blkg_rwstat {
+ struct u64_stats_sync syncp;
+ uint64_t cnt[BLKG_RWSTAT_NR];
+};
+
struct blkio_group_stats {
- struct u64_stats_sync syncp;
+ /* number of ios merged */
+ struct blkg_rwstat merged;
+ /* total time spent on device in ns, may not be accurate w/ queueing */
+ struct blkg_rwstat service_time;
+ /* total time spent waiting in scheduler queue in ns */
+ struct blkg_rwstat wait_time;
+ /* number of IOs queued up */
+ struct blkg_rwstat queued;
/* total disk time and nr sectors dispatched by this group */
- uint64_t time;
- uint64_t stat_arr[BLKIO_STAT_ARR_NR][BLKIO_STAT_TOTAL];
+ struct blkg_stat time;
#ifdef CONFIG_DEBUG_BLK_CGROUP
- /* Time not charged to this cgroup */
- uint64_t unaccounted_time;
-
- /* Sum of number of IOs queued across all samples */
- uint64_t avg_queue_size_sum;
- /* Count of samples taken for average */
- uint64_t avg_queue_size_samples;
- /* How many times this group has been removed from service tree */
- unsigned long dequeue;
-
- /* Total time spent waiting for it to be assigned a timeslice. */
- uint64_t group_wait_time;
-
- /* Time spent idling for this blkio_group */
- uint64_t idle_time;
- /*
- * Total time when we have requests queued and do not contain the
- * current active queue.
- */
- uint64_t empty_time;
-
+ /* time not charged to this cgroup */
+ struct blkg_stat unaccounted_time;
+ /* sum of number of ios queued across all samples */
+ struct blkg_stat avg_queue_size_sum;
+ /* count of samples taken for average */
+ struct blkg_stat avg_queue_size_samples;
+ /* how many times this group has been removed from service tree */
+ struct blkg_stat dequeue;
+ /* total time spent waiting for it to be assigned a timeslice. */
+ struct blkg_stat group_wait_time;
+ /* time spent idling for this blkio_group */
+ struct blkg_stat idle_time;
+ /* total time with empty current active q with other requests queued */
+ struct blkg_stat empty_time;
/* fields after this shouldn't be cleared on stat reset */
- uint64_t start_group_wait_time;
- uint64_t start_idle_time;
- uint64_t start_empty_time;
- uint16_t flags;
+ uint64_t start_group_wait_time;
+ uint64_t start_idle_time;
+ uint64_t start_empty_time;
+ uint16_t flags;
#endif
};
-#ifdef CONFIG_DEBUG_BLK_CGROUP
-#define BLKG_STATS_DEBUG_CLEAR_START \
- offsetof(struct blkio_group_stats, unaccounted_time)
-#define BLKG_STATS_DEBUG_CLEAR_SIZE \
- (offsetof(struct blkio_group_stats, start_group_wait_time) - \
- BLKG_STATS_DEBUG_CLEAR_START)
-#endif
-
/* Per cpu blkio group stats */
struct blkio_group_stats_cpu {
- uint64_t sectors;
- uint64_t stat_arr_cpu[BLKIO_STAT_CPU_ARR_NR][BLKIO_STAT_TOTAL];
- struct u64_stats_sync syncp;
+ /* total bytes transferred */
+ struct blkg_rwstat service_bytes;
+ /* total IOs serviced, post merge */
+ struct blkg_rwstat serviced;
+ /* total sectors transferred */
+ struct blkg_stat sectors;
};
struct blkio_group_conf {
@@ -316,6 +322,121 @@ static inline void blkg_put(struct blkio_group *blkg)
__blkg_release(blkg);
}
+/**
+ * blkg_stat_add - add a value to a blkg_stat
+ * @stat: target blkg_stat
+ * @val: value to add
+ *
+ * Add @val to @stat. The caller is responsible for synchronizing calls to
+ * this function.
+ */
+static inline void blkg_stat_add(struct blkg_stat *stat, uint64_t val)
+{
+ u64_stats_update_begin(&stat->syncp);
+ stat->cnt += val;
+ u64_stats_update_end(&stat->syncp);
+}
+
+/**
+ * blkg_stat_read - read the current value of a blkg_stat
+ * @stat: blkg_stat to read
+ *
+ * Read the current value of @stat. This function can be called without
+ * synchroniztion and takes care of u64 atomicity.
+ */
+static inline uint64_t blkg_stat_read(struct blkg_stat *stat)
+{
+ unsigned int start;
+ uint64_t v;
+
+ do {
+ start = u64_stats_fetch_begin(&stat->syncp);
+ v = stat->cnt;
+ } while (u64_stats_fetch_retry(&stat->syncp, start));
+
+ return v;
+}
+
+/**
+ * blkg_stat_reset - reset a blkg_stat
+ * @stat: blkg_stat to reset
+ */
+static inline void blkg_stat_reset(struct blkg_stat *stat)
+{
+ stat->cnt = 0;
+}
+
+/**
+ * blkg_rwstat_add - add a value to a blkg_rwstat
+ * @rwstat: target blkg_rwstat
+ * @rw: mask of REQ_{WRITE|SYNC}
+ * @val: value to add
+ *
+ * Add @val to @rwstat. The counters are chosen according to @rw. The
+ * caller is responsible for synchronizing calls to this function.
+ */
+static inline void blkg_rwstat_add(struct blkg_rwstat *rwstat,
+ int rw, uint64_t val)
+{
+ u64_stats_update_begin(&rwstat->syncp);
+
+ if (rw & REQ_WRITE)
+ rwstat->cnt[BLKG_RWSTAT_WRITE] += val;
+ else
+ rwstat->cnt[BLKG_RWSTAT_READ] += val;
+ if (rw & REQ_SYNC)
+ rwstat->cnt[BLKG_RWSTAT_SYNC] += val;
+ else
+ rwstat->cnt[BLKG_RWSTAT_ASYNC] += val;
+
+ u64_stats_update_end(&rwstat->syncp);
+}
+
+/**
+ * blkg_rwstat_read - read the current values of a blkg_rwstat
+ * @rwstat: blkg_rwstat to read
+ *
+ * Read the current snapshot of @rwstat and return it as the return value.
+ * This function can be called without synchronization and takes care of
+ * u64 atomicity.
+ */
+static struct blkg_rwstat blkg_rwstat_read(struct blkg_rwstat *rwstat)
+{
+ unsigned int start;
+ struct blkg_rwstat tmp;
+
+ do {
+ start = u64_stats_fetch_begin(&rwstat->syncp);
+ tmp = *rwstat;
+ } while (u64_stats_fetch_retry(&rwstat->syncp, start));
+
+ return tmp;
+}
+
+/**
+ * blkg_rwstat_sum - read the total count of a blkg_rwstat
+ * @rwstat: blkg_rwstat to read
+ *
+ * Return the total count of @rwstat regardless of the IO direction. This
+ * function can be called without synchronization and takes care of u64
+ * atomicity.
+ */
+static inline uint64_t blkg_rwstat_sum(struct blkg_rwstat *rwstat)
+{
+ struct blkg_rwstat tmp = blkg_rwstat_read(rwstat);
+
+ return tmp.cnt[BLKG_RWSTAT_READ] + tmp.cnt[BLKG_RWSTAT_WRITE];
+}
+
+/**
+ * blkg_rwstat_reset - reset a blkg_rwstat
+ * @rwstat: blkg_rwstat to reset
+ */
+static inline void blkg_rwstat_reset(struct blkg_rwstat *rwstat)
+{
+ memset(rwstat->cnt, 0, sizeof(rwstat->cnt));
+}
+
#else
struct blkio_group {