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Date: Tue, 30 Apr 2019 10:34:14 +0300
From: "Pavel Begunkov (Silence)" <asml.silence@...il.com>
To: Jens Axboe <axboe@...nel.dk>, linux-block@...r.kernel.org,
linux-kernel@...r.kernel.org
Cc: Pavel Begunkov <asml.silence@...il.com>
Subject: [PATCH 2/7] blk-stats: Introduce explicit stat staging buffers
From: Pavel Begunkov <asml.silence@...il.com>
struct blk_rq_stat could be in one of two implicit states, which use
different set of fields:
1. per-cpu intermediate (i.e. staging) (keep batch, invalid mean)
2. calculated stats (see blk_rq_stat_collect) (w/o batch, w/ mean)
blk_rq_stat_*() expect their arguments to be in the right state, and it
is not documented in which. That's error prone.
Split blk_rq_stat into 2 structs corresponding to one of the states.
That requires some code duplication, but
1. prevents misuses (compile-time type-system check)
2. reduces memory needed
3. makes it easier to extend stats
Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
---
block/blk-iolatency.c | 41 +++++++++++++++++++++++++++++----------
block/blk-stat.c | 30 +++++++++++++++++-----------
block/blk-stat.h | 8 +++++---
include/linux/blk_types.h | 6 ++++++
4 files changed, 61 insertions(+), 24 deletions(-)
diff --git a/block/blk-iolatency.c b/block/blk-iolatency.c
index 4010152ebeb2..df9d37398a0f 100644
--- a/block/blk-iolatency.c
+++ b/block/blk-iolatency.c
@@ -129,9 +129,16 @@ struct latency_stat {
};
};
+struct latency_stat_staging {
+ union {
+ struct percentile_stats ps;
+ struct blk_rq_stat_staging rqs;
+ };
+};
+
struct iolatency_grp {
struct blkg_policy_data pd;
- struct latency_stat __percpu *stats;
+ struct latency_stat_staging __percpu *stats;
struct latency_stat cur_stat;
struct blk_iolatency *blkiolat;
struct rq_depth rq_depth;
@@ -198,6 +205,16 @@ static inline void latency_stat_init(struct iolatency_grp *iolat,
blk_rq_stat_init(&stat->rqs);
}
+static inline void latency_stat_init_staging(struct iolatency_grp *iolat,
+ struct latency_stat_staging *stat)
+{
+ if (iolat->ssd) {
+ stat->ps.total = 0;
+ stat->ps.missed = 0;
+ } else
+ blk_rq_stat_init_staging(&stat->rqs);
+}
+
static inline void latency_stat_merge(struct iolatency_grp *iolat,
struct latency_stat *sum,
struct latency_stat *stat)
@@ -211,7 +228,7 @@ static inline void latency_stat_merge(struct iolatency_grp *iolat,
static inline void latency_stat_collect(struct iolatency_grp *iolat,
struct latency_stat *sum,
- struct latency_stat *stat)
+ struct latency_stat_staging *stat)
{
if (iolat->ssd) {
sum->ps.total += stat->ps.total;
@@ -223,7 +240,8 @@ static inline void latency_stat_collect(struct iolatency_grp *iolat,
static inline void latency_stat_record_time(struct iolatency_grp *iolat,
u64 req_time)
{
- struct latency_stat *stat = get_cpu_ptr(iolat->stats);
+ struct latency_stat_staging *stat = get_cpu_ptr(iolat->stats);
+
if (iolat->ssd) {
if (req_time >= iolat->min_lat_nsec)
stat->ps.missed++;
@@ -539,10 +557,11 @@ static void iolatency_check_latencies(struct iolatency_grp *iolat, u64 now)
latency_stat_init(iolat, &stat);
preempt_disable();
for_each_online_cpu(cpu) {
- struct latency_stat *s;
+ struct latency_stat_staging *s;
+
s = per_cpu_ptr(iolat->stats, cpu);
latency_stat_collect(iolat, &stat, s);
- latency_stat_init(iolat, s);
+ latency_stat_init_staging(iolat, s);
}
preempt_enable();
@@ -921,7 +940,8 @@ static size_t iolatency_ssd_stat(struct iolatency_grp *iolat, char *buf,
latency_stat_init(iolat, &stat);
preempt_disable();
for_each_online_cpu(cpu) {
- struct latency_stat *s;
+ struct latency_stat_staging *s;
+
s = per_cpu_ptr(iolat->stats, cpu);
latency_stat_collect(iolat, &stat, s);
}
@@ -965,8 +985,8 @@ static struct blkg_policy_data *iolatency_pd_alloc(gfp_t gfp, int node)
iolat = kzalloc_node(sizeof(*iolat), gfp, node);
if (!iolat)
return NULL;
- iolat->stats = __alloc_percpu_gfp(sizeof(struct latency_stat),
- __alignof__(struct latency_stat), gfp);
+ iolat->stats = __alloc_percpu_gfp(sizeof(struct latency_stat_staging),
+ __alignof__(struct latency_stat_staging), gfp);
if (!iolat->stats) {
kfree(iolat);
return NULL;
@@ -989,9 +1009,10 @@ static void iolatency_pd_init(struct blkg_policy_data *pd)
iolat->ssd = false;
for_each_possible_cpu(cpu) {
- struct latency_stat *stat;
+ struct latency_stat_staging *stat;
+
stat = per_cpu_ptr(iolat->stats, cpu);
- latency_stat_init(iolat, stat);
+ latency_stat_init_staging(iolat, stat);
}
latency_stat_init(iolat, &iolat->cur_stat);
diff --git a/block/blk-stat.c b/block/blk-stat.c
index a6da68af45db..13f93249fd5f 100644
--- a/block/blk-stat.c
+++ b/block/blk-stat.c
@@ -17,15 +17,22 @@ struct blk_queue_stats {
bool enable_accounting;
};
+void blk_rq_stat_init_staging(struct blk_rq_stat_staging *stat)
+{
+ stat->min = -1ULL;
+ stat->max = 0;
+ stat->batch = 0;
+ stat->nr_samples = 0;
+}
+
void blk_rq_stat_init(struct blk_rq_stat *stat)
{
stat->min = -1ULL;
stat->max = stat->nr_samples = stat->mean = 0;
- stat->batch = 0;
}
-/* src is a per-cpu stat, mean isn't initialized */
-void blk_rq_stat_collect(struct blk_rq_stat *dst, struct blk_rq_stat *src)
+void blk_rq_stat_collect(struct blk_rq_stat *dst,
+ struct blk_rq_stat_staging *src)
{
if (!src->nr_samples)
return;
@@ -54,7 +61,7 @@ void blk_rq_stat_merge(struct blk_rq_stat *dst, struct blk_rq_stat *src)
dst->nr_samples += src->nr_samples;
}
-void blk_rq_stat_add(struct blk_rq_stat *stat, u64 value)
+void blk_rq_stat_add(struct blk_rq_stat_staging *stat, u64 value)
{
stat->min = min(stat->min, value);
stat->max = max(stat->max, value);
@@ -66,7 +73,7 @@ void blk_stat_add(struct request *rq, u64 now)
{
struct request_queue *q = rq->q;
struct blk_stat_callback *cb;
- struct blk_rq_stat *stat;
+ struct blk_rq_stat_staging *stat;
int bucket;
u64 value;
@@ -100,13 +107,13 @@ static void blk_stat_timer_fn(struct timer_list *t)
blk_rq_stat_init(&cb->stat[bucket]);
for_each_online_cpu(cpu) {
- struct blk_rq_stat *cpu_stat;
+ struct blk_rq_stat_staging *cpu_stat;
cpu_stat = per_cpu_ptr(cb->cpu_stat, cpu);
for (bucket = 0; bucket < cb->buckets; bucket++) {
blk_rq_stat_collect(&cb->stat[bucket],
&cpu_stat[bucket]);
- blk_rq_stat_init(&cpu_stat[bucket]);
+ blk_rq_stat_init_staging(&cpu_stat[bucket]);
}
}
@@ -130,8 +137,9 @@ blk_stat_alloc_callback(void (*timer_fn)(struct blk_stat_callback *),
kfree(cb);
return NULL;
}
- cb->cpu_stat = __alloc_percpu(buckets * sizeof(struct blk_rq_stat),
- __alignof__(struct blk_rq_stat));
+ cb->cpu_stat = __alloc_percpu(
+ buckets * sizeof(struct blk_rq_stat_staging),
+ __alignof__(struct blk_rq_stat_staging));
if (!cb->cpu_stat) {
kfree(cb->stat);
kfree(cb);
@@ -154,11 +162,11 @@ void blk_stat_add_callback(struct request_queue *q,
int cpu;
for_each_possible_cpu(cpu) {
- struct blk_rq_stat *cpu_stat;
+ struct blk_rq_stat_staging *cpu_stat;
cpu_stat = per_cpu_ptr(cb->cpu_stat, cpu);
for (bucket = 0; bucket < cb->buckets; bucket++)
- blk_rq_stat_init(&cpu_stat[bucket]);
+ blk_rq_stat_init_staging(&cpu_stat[bucket]);
}
spin_lock(&q->stats->lock);
diff --git a/block/blk-stat.h b/block/blk-stat.h
index 5597ecc34ef5..e5c753fbd6e6 100644
--- a/block/blk-stat.h
+++ b/block/blk-stat.h
@@ -30,7 +30,7 @@ struct blk_stat_callback {
/**
* @cpu_stat: Per-cpu statistics buckets.
*/
- struct blk_rq_stat __percpu *cpu_stat;
+ struct blk_rq_stat_staging __percpu *cpu_stat;
/**
* @bucket_fn: Given a request, returns which statistics bucket it
@@ -164,9 +164,11 @@ static inline void blk_stat_activate_msecs(struct blk_stat_callback *cb,
mod_timer(&cb->timer, jiffies + msecs_to_jiffies(msecs));
}
-void blk_rq_stat_add(struct blk_rq_stat *, u64);
-void blk_rq_stat_collect(struct blk_rq_stat *dst, struct blk_rq_stat *src);
+void blk_rq_stat_add(struct blk_rq_stat_staging *stat, u64);
+void blk_rq_stat_collect(struct blk_rq_stat *dst,
+ struct blk_rq_stat_staging *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 *);
+void blk_rq_stat_init_staging(struct blk_rq_stat_staging *stat);
#endif
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 791fee35df88..5718a4e2e731 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -446,7 +446,13 @@ struct blk_rq_stat {
u64 min;
u64 max;
u32 nr_samples;
+};
+
+struct blk_rq_stat_staging {
+ u64 min;
+ u64 max;
u64 batch;
+ u32 nr_samples;
};
#endif /* __LINUX_BLK_TYPES_H */
--
2.21.0
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