From: Pavel Begunkov <[email protected]> struct blk_rq_stat has two implicit states in which it can be: (1) per-cpu intermediate stats (i.e. staging, intermediate) (2) final stats / aggregation of (1) (see blk_rq_stat_collect)
The states use different sets of fields. E.g. (1) uses @batch but not @mean, and vise versa for (2). So, any function that uses struct blk_rq_stat has implicit assumptions about the states. blk_rq_stat_sum() expects @src to be in (1) and @dst in (2). iolatency_check_latencies() violates that (passing struct blk_rq_stat, previously used as @dst, as @src). As a result, iolat->cur_stat.rqs.mean is always 0 for non-ssd devices. Use 2 distinct functions instead: one to collect intermediate stats (i.e. with valid batch), and the second one for merging already accumulated stats (i.e. with valid mean). Signed-off-by: Pavel Begunkov <[email protected]> --- block/blk-iolatency.c | 21 ++++++++++++++++----- block/blk-stat.c | 20 ++++++++++++++++++-- block/blk-stat.h | 3 ++- 3 files changed, 36 insertions(+), 8 deletions(-) diff --git a/block/blk-iolatency.c b/block/blk-iolatency.c index d22e61bced86..fc8ce1a0ae21 100644 --- a/block/blk-iolatency.c +++ b/block/blk-iolatency.c @@ -199,7 +199,7 @@ static inline void latency_stat_init(struct iolatency_grp *iolat, blk_rq_stat_init(&stat->rqs); } -static inline void latency_stat_sum(struct iolatency_grp *iolat, +static inline void latency_stat_merge(struct iolatency_grp *iolat, struct latency_stat *sum, struct latency_stat *stat) { @@ -207,7 +207,18 @@ static inline void latency_stat_sum(struct iolatency_grp *iolat, sum->ps.total += stat->ps.total; sum->ps.missed += stat->ps.missed; } else - blk_rq_stat_sum(&sum->rqs, &stat->rqs); + blk_rq_stat_merge(&sum->rqs, &stat->rqs); +} + +static inline void latency_stat_collect(struct iolatency_grp *iolat, + struct latency_stat *sum, + struct latency_stat *stat) +{ + if (iolat->ssd) { + sum->ps.total += stat->ps.total; + sum->ps.missed += stat->ps.missed; + } else + blk_rq_stat_collect(&sum->rqs, &stat->rqs); } static inline void latency_stat_record_time(struct iolatency_grp *iolat, @@ -531,7 +542,7 @@ static void iolatency_check_latencies(struct iolatency_grp *iolat, u64 now) for_each_online_cpu(cpu) { struct latency_stat *s; s = per_cpu_ptr(iolat->stats, cpu); - latency_stat_sum(iolat, &stat, s); + latency_stat_collect(iolat, &stat, s); latency_stat_init(iolat, s); } preempt_enable(); @@ -552,7 +563,7 @@ static void iolatency_check_latencies(struct iolatency_grp *iolat, u64 now) /* Somebody beat us to the punch, just bail. */ spin_lock_irqsave(&lat_info->lock, flags); - latency_stat_sum(iolat, &iolat->cur_stat, &stat); + latency_stat_merge(iolat, &iolat->cur_stat, &stat); lat_info->nr_samples -= iolat->nr_samples; lat_info->nr_samples += latency_stat_samples(iolat, &iolat->cur_stat); iolat->nr_samples = latency_stat_samples(iolat, &iolat->cur_stat); @@ -913,7 +924,7 @@ static size_t iolatency_ssd_stat(struct iolatency_grp *iolat, char *buf, for_each_online_cpu(cpu) { struct latency_stat *s; s = per_cpu_ptr(iolat->stats, cpu); - latency_stat_sum(iolat, &stat, s); + latency_stat_collect(iolat, &stat, s); } preempt_enable(); diff --git a/block/blk-stat.c b/block/blk-stat.c index 940f15d600f8..78389182b5d0 100644 --- a/block/blk-stat.c +++ b/block/blk-stat.c @@ -26,7 +26,7 @@ void blk_rq_stat_init(struct blk_rq_stat *stat) } /* src is a per-cpu stat, mean isn't initialized */ -void blk_rq_stat_sum(struct blk_rq_stat *dst, struct blk_rq_stat *src) +void blk_rq_stat_collect(struct blk_rq_stat *dst, struct blk_rq_stat *src) { if (!src->nr_samples) return; @@ -40,6 +40,21 @@ void blk_rq_stat_sum(struct blk_rq_stat *dst, struct blk_rq_stat *src) dst->nr_samples += src->nr_samples; } +void blk_rq_stat_merge(struct blk_rq_stat *dst, struct blk_rq_stat *src) +{ + if (!src->nr_samples) + return; + + dst->min = min(dst->min, src->min); + dst->max = max(dst->max, src->max); + + dst->mean = div_u64(src->mean * src->nr_samples + + dst->mean * dst->nr_samples, + dst->nr_samples + src->nr_samples); + + dst->nr_samples += src->nr_samples; +} + void blk_rq_stat_add(struct blk_rq_stat *stat, u64 value) { stat->min = min(stat->min, value); @@ -90,7 +105,8 @@ static void blk_stat_timer_fn(struct timer_list *t) cpu_stat = per_cpu_ptr(cb->cpu_stat, cpu); for (bucket = 0; bucket < cb->buckets; bucket++) { - blk_rq_stat_sum(&cb->stat[bucket], &cpu_stat[bucket]); + blk_rq_stat_collect(&cb->stat[bucket], + &cpu_stat[bucket]); blk_rq_stat_init(&cpu_stat[bucket]); } } diff --git a/block/blk-stat.h b/block/blk-stat.h index 17b47a86eefb..5597ecc34ef5 100644 --- a/block/blk-stat.h +++ b/block/blk-stat.h @@ -165,7 +165,8 @@ static inline void blk_stat_activate_msecs(struct blk_stat_callback *cb, } void blk_rq_stat_add(struct blk_rq_stat *, u64); -void blk_rq_stat_sum(struct blk_rq_stat *, struct blk_rq_stat *); +void blk_rq_stat_collect(struct blk_rq_stat *dst, struct blk_rq_stat *src); +void blk_rq_stat_merge(struct blk_rq_stat *dst, struct blk_rq_stat *src); void blk_rq_stat_init(struct blk_rq_stat *); #endif -- 2.22.0
