From 24bdb8ef068ebdc2a57ce715f0ab22d5da32832a Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Tue, 18 Aug 2015 14:55:22 -0700 Subject: blkcg: make blkcg_[rw]stat per-cpu blkcg_[rw]stat are used as stat counters for blkcg policies. It isn't per-cpu by itself and blk-throttle makes it per-cpu by wrapping around it. This patch makes blkcg_[rw]stat per-cpu and drop the ad-hoc per-cpu wrapping in blk-throttle. * blkg_[rw]stat->cnt is replaced with cpu_cnt which is struct percpu_counter. This makes syncp unnecessary as remote accesses are handled by percpu_counter itself. * blkg_[rw]stat_init() can now fail due to percpu allocation failure and thus are updated to return int. * percpu_counters need explicit freeing. blkg_[rw]stat_exit() added. * As blkg_rwstat->cpu_cnt[] can't be read directly anymore, reading and summing results are stored in ->aux_cnt[] instead. * Custom per-cpu stat implementation in blk-throttle is removed. This makes all blkcg stat counters per-cpu without complicating policy implmentations. Signed-off-by: Tejun Heo Cc: Vivek Goyal Signed-off-by: Jens Axboe --- include/linux/blk-cgroup.h | 120 +++++++++++++++++++++++++-------------------- 1 file changed, 67 insertions(+), 53 deletions(-) (limited to 'include/linux/blk-cgroup.h') diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h index e8092276af58..fdc7ac08b1ce 100644 --- a/include/linux/blk-cgroup.h +++ b/include/linux/blk-cgroup.h @@ -14,12 +14,15 @@ */ #include -#include +#include #include #include #include #include +/* percpu_counter batch for blkg_[rw]stats, per-cpu drift doesn't matter */ +#define BLKG_STAT_CPU_BATCH (INT_MAX / 2) + /* Max limits for throttle policy */ #define THROTL_IOPS_MAX UINT_MAX @@ -55,17 +58,16 @@ struct blkcg { /* * blkg_[rw]stat->aux_cnt is excluded for local stats but included for - * recursive. Used to carry stats of dead children. + * recursive. Used to carry stats of dead children, and, for blkg_rwstat, + * to carry result values from read and sum operations. */ struct blkg_stat { - struct u64_stats_sync syncp; - uint64_t cnt; + struct percpu_counter cpu_cnt; atomic64_t aux_cnt; }; struct blkg_rwstat { - struct u64_stats_sync syncp; - uint64_t cnt[BLKG_RWSTAT_NR]; + struct percpu_counter cpu_cnt[BLKG_RWSTAT_NR]; atomic64_t aux_cnt[BLKG_RWSTAT_NR]; }; @@ -486,10 +488,21 @@ struct request_list *__blk_queue_next_rl(struct request_list *rl, #define blk_queue_for_each_rl(rl, q) \ for ((rl) = &(q)->root_rl; (rl); (rl) = __blk_queue_next_rl((rl), (q))) -static inline void blkg_stat_init(struct blkg_stat *stat) +static inline int blkg_stat_init(struct blkg_stat *stat, gfp_t gfp) { - u64_stats_init(&stat->syncp); + int ret; + + ret = percpu_counter_init(&stat->cpu_cnt, 0, gfp); + if (ret) + return ret; + atomic64_set(&stat->aux_cnt, 0); + return 0; +} + +static inline void blkg_stat_exit(struct blkg_stat *stat) +{ + percpu_counter_destroy(&stat->cpu_cnt); } /** @@ -497,35 +510,21 @@ static inline void blkg_stat_init(struct blkg_stat *stat) * @stat: target blkg_stat * @val: value to add * - * Add @val to @stat. The caller is responsible for synchronizing calls to - * this function. + * Add @val to @stat. The caller must ensure that IRQ on the same CPU + * don't re-enter this function for the same counter. */ 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); + __percpu_counter_add(&stat->cpu_cnt, val, BLKG_STAT_CPU_BATCH); } /** * blkg_stat_read - read the current value of a blkg_stat * @stat: blkg_stat to read - * - * Read the current value of @stat. The returned value doesn't include the - * aux count. 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_irq(&stat->syncp); - v = stat->cnt; - } while (u64_stats_fetch_retry_irq(&stat->syncp, start)); - - return v; + return percpu_counter_sum_positive(&stat->cpu_cnt); } /** @@ -534,7 +533,7 @@ static inline uint64_t blkg_stat_read(struct blkg_stat *stat) */ static inline void blkg_stat_reset(struct blkg_stat *stat) { - stat->cnt = 0; + percpu_counter_set(&stat->cpu_cnt, 0); atomic64_set(&stat->aux_cnt, 0); } @@ -552,14 +551,28 @@ static inline void blkg_stat_add_aux(struct blkg_stat *to, &to->aux_cnt); } -static inline void blkg_rwstat_init(struct blkg_rwstat *rwstat) +static inline int blkg_rwstat_init(struct blkg_rwstat *rwstat, gfp_t gfp) { - int i; + int i, ret; + + for (i = 0; i < BLKG_RWSTAT_NR; i++) { + ret = percpu_counter_init(&rwstat->cpu_cnt[i], 0, gfp); + if (ret) { + while (--i >= 0) + percpu_counter_destroy(&rwstat->cpu_cnt[i]); + return ret; + } + atomic64_set(&rwstat->aux_cnt[i], 0); + } + return 0; +} - u64_stats_init(&rwstat->syncp); +static inline void blkg_rwstat_exit(struct blkg_rwstat *rwstat) +{ + int i; for (i = 0; i < BLKG_RWSTAT_NR; i++) - atomic64_set(&rwstat->aux_cnt[i], 0); + percpu_counter_destroy(&rwstat->cpu_cnt[i]); } /** @@ -574,39 +587,38 @@ static inline void blkg_rwstat_init(struct blkg_rwstat *rwstat) static inline void blkg_rwstat_add(struct blkg_rwstat *rwstat, int rw, uint64_t val) { - u64_stats_update_begin(&rwstat->syncp); + struct percpu_counter *cnt; if (rw & REQ_WRITE) - rwstat->cnt[BLKG_RWSTAT_WRITE] += val; + cnt = &rwstat->cpu_cnt[BLKG_RWSTAT_WRITE]; else - rwstat->cnt[BLKG_RWSTAT_READ] += val; + cnt = &rwstat->cpu_cnt[BLKG_RWSTAT_READ]; + + __percpu_counter_add(cnt, val, BLKG_STAT_CPU_BATCH); + if (rw & REQ_SYNC) - rwstat->cnt[BLKG_RWSTAT_SYNC] += val; + cnt = &rwstat->cpu_cnt[BLKG_RWSTAT_SYNC]; else - rwstat->cnt[BLKG_RWSTAT_ASYNC] += val; + cnt = &rwstat->cpu_cnt[BLKG_RWSTAT_ASYNC]; - u64_stats_update_end(&rwstat->syncp); + __percpu_counter_add(cnt, val, BLKG_STAT_CPU_BATCH); } /** * 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. + * Read the current snapshot of @rwstat and return it in the aux counts. */ static inline struct blkg_rwstat blkg_rwstat_read(struct blkg_rwstat *rwstat) { - unsigned int start; - struct blkg_rwstat tmp; - - do { - start = u64_stats_fetch_begin_irq(&rwstat->syncp); - tmp = *rwstat; - } while (u64_stats_fetch_retry_irq(&rwstat->syncp, start)); + struct blkg_rwstat result; + int i; - return tmp; + for (i = 0; i < BLKG_RWSTAT_NR; i++) + atomic64_set(&result.aux_cnt[i], + percpu_counter_sum_positive(&rwstat->cpu_cnt[i])); + return result; } /** @@ -621,7 +633,8 @@ static inline uint64_t blkg_rwstat_total(struct blkg_rwstat *rwstat) { struct blkg_rwstat tmp = blkg_rwstat_read(rwstat); - return tmp.cnt[BLKG_RWSTAT_READ] + tmp.cnt[BLKG_RWSTAT_WRITE]; + return atomic64_read(&tmp.aux_cnt[BLKG_RWSTAT_READ]) + + atomic64_read(&tmp.aux_cnt[BLKG_RWSTAT_WRITE]); } /** @@ -632,10 +645,10 @@ static inline void blkg_rwstat_reset(struct blkg_rwstat *rwstat) { int i; - memset(rwstat->cnt, 0, sizeof(rwstat->cnt)); - - for (i = 0; i < BLKG_RWSTAT_NR; i++) + for (i = 0; i < BLKG_RWSTAT_NR; i++) { + percpu_counter_set(&rwstat->cpu_cnt[i], 0); atomic64_set(&rwstat->aux_cnt[i], 0); + } } /** @@ -652,7 +665,8 @@ static inline void blkg_rwstat_add_aux(struct blkg_rwstat *to, int i; for (i = 0; i < BLKG_RWSTAT_NR; i++) - atomic64_add(v.cnt[i] + atomic64_read(&from->aux_cnt[i]), + atomic64_add(atomic64_read(&v.aux_cnt[i]) + + atomic64_read(&from->aux_cnt[i]), &to->aux_cnt[i]); } -- cgit v1.2.3-59-g8ed1b