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authorJoseph Qi <qijiang.qj@alibaba-inc.com>2017-11-21 09:38:30 +0800
committerJens Axboe <axboe@kernel.dk>2018-01-18 19:51:08 -0700
commitb889bf66d001a46a95deef18ddbe6db84645ed24 (patch)
treef3739a244b423ccbfb4702f0a5218edca32252f4 /block/blk-throttle.c
parenta13553c777375009584741e7d9982e775c4b0744 (diff)
downloadlinux-0-day-b889bf66d001a46a95deef18ddbe6db84645ed24.tar.gz
blk-throttle: track read and write request individually
In mixed read/write workload on SSD, write latency is much lower than read. But now we only track and record read latency and then use it as threshold base for both read and write io latency accounting. As a result, write io latency will always be considered as good and bad_bio_cnt is much smaller than 20% of bio_cnt. That is to mean, the tg to be checked will be treated as idle most of the time and still let others dispatch more ios, even it is truly running under low limit and wants its low limit to be guaranteed, which is not we expected in fact. So track read and write request individually, which can bring more precise latency control for low limit idle detection. Signed-off-by: Joseph Qi <qijiang.qj@alibaba-inc.com> Reviewed-by: Shaohua Li <shli@fb.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/blk-throttle.c')
-rw-r--r--block/blk-throttle.c134
1 files changed, 79 insertions, 55 deletions
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index e842841..e136f5e 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -216,9 +216,9 @@ struct throtl_data
unsigned int scale;
- struct latency_bucket tmp_buckets[LATENCY_BUCKET_SIZE];
- struct avg_latency_bucket avg_buckets[LATENCY_BUCKET_SIZE];
- struct latency_bucket __percpu *latency_buckets;
+ struct latency_bucket tmp_buckets[2][LATENCY_BUCKET_SIZE];
+ struct avg_latency_bucket avg_buckets[2][LATENCY_BUCKET_SIZE];
+ struct latency_bucket __percpu *latency_buckets[2];
unsigned long last_calculate_time;
unsigned long filtered_latency;
@@ -2050,10 +2050,10 @@ static void blk_throtl_update_idletime(struct throtl_grp *tg)
#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
static void throtl_update_latency_buckets(struct throtl_data *td)
{
- struct avg_latency_bucket avg_latency[LATENCY_BUCKET_SIZE];
- int i, cpu;
- unsigned long last_latency = 0;
- unsigned long latency;
+ struct avg_latency_bucket avg_latency[2][LATENCY_BUCKET_SIZE];
+ int i, cpu, rw;
+ unsigned long last_latency[2] = { 0 };
+ unsigned long latency[2];
if (!blk_queue_nonrot(td->queue))
return;
@@ -2062,56 +2062,67 @@ static void throtl_update_latency_buckets(struct throtl_data *td)
td->last_calculate_time = jiffies;
memset(avg_latency, 0, sizeof(avg_latency));
- for (i = 0; i < LATENCY_BUCKET_SIZE; i++) {
- struct latency_bucket *tmp = &td->tmp_buckets[i];
-
- for_each_possible_cpu(cpu) {
- struct latency_bucket *bucket;
-
- /* this isn't race free, but ok in practice */
- bucket = per_cpu_ptr(td->latency_buckets, cpu);
- tmp->total_latency += bucket[i].total_latency;
- tmp->samples += bucket[i].samples;
- bucket[i].total_latency = 0;
- bucket[i].samples = 0;
- }
+ for (rw = READ; rw <= WRITE; rw++) {
+ for (i = 0; i < LATENCY_BUCKET_SIZE; i++) {
+ struct latency_bucket *tmp = &td->tmp_buckets[rw][i];
+
+ for_each_possible_cpu(cpu) {
+ struct latency_bucket *bucket;
+
+ /* this isn't race free, but ok in practice */
+ bucket = per_cpu_ptr(td->latency_buckets[rw],
+ cpu);
+ tmp->total_latency += bucket[i].total_latency;
+ tmp->samples += bucket[i].samples;
+ bucket[i].total_latency = 0;
+ bucket[i].samples = 0;
+ }
- if (tmp->samples >= 32) {
- int samples = tmp->samples;
+ if (tmp->samples >= 32) {
+ int samples = tmp->samples;
- latency = tmp->total_latency;
+ latency[rw] = tmp->total_latency;
- tmp->total_latency = 0;
- tmp->samples = 0;
- latency /= samples;
- if (latency == 0)
- continue;
- avg_latency[i].latency = latency;
+ tmp->total_latency = 0;
+ tmp->samples = 0;
+ latency[rw] /= samples;
+ if (latency[rw] == 0)
+ continue;
+ avg_latency[rw][i].latency = latency[rw];
+ }
}
}
- for (i = 0; i < LATENCY_BUCKET_SIZE; i++) {
- if (!avg_latency[i].latency) {
- if (td->avg_buckets[i].latency < last_latency)
- td->avg_buckets[i].latency = last_latency;
- continue;
- }
+ for (rw = READ; rw <= WRITE; rw++) {
+ for (i = 0; i < LATENCY_BUCKET_SIZE; i++) {
+ if (!avg_latency[rw][i].latency) {
+ if (td->avg_buckets[rw][i].latency < last_latency[rw])
+ td->avg_buckets[rw][i].latency =
+ last_latency[rw];
+ continue;
+ }
- if (!td->avg_buckets[i].valid)
- latency = avg_latency[i].latency;
- else
- latency = (td->avg_buckets[i].latency * 7 +
- avg_latency[i].latency) >> 3;
+ if (!td->avg_buckets[rw][i].valid)
+ latency[rw] = avg_latency[rw][i].latency;
+ else
+ latency[rw] = (td->avg_buckets[rw][i].latency * 7 +
+ avg_latency[rw][i].latency) >> 3;
- td->avg_buckets[i].latency = max(latency, last_latency);
- td->avg_buckets[i].valid = true;
- last_latency = td->avg_buckets[i].latency;
+ td->avg_buckets[rw][i].latency = max(latency[rw],
+ last_latency[rw]);
+ td->avg_buckets[rw][i].valid = true;
+ last_latency[rw] = td->avg_buckets[rw][i].latency;
+ }
}
for (i = 0; i < LATENCY_BUCKET_SIZE; i++)
throtl_log(&td->service_queue,
- "Latency bucket %d: latency=%ld, valid=%d", i,
- td->avg_buckets[i].latency, td->avg_buckets[i].valid);
+ "Latency bucket %d: read latency=%ld, read valid=%d, "
+ "write latency=%ld, write valid=%d", i,
+ td->avg_buckets[READ][i].latency,
+ td->avg_buckets[READ][i].valid,
+ td->avg_buckets[WRITE][i].latency,
+ td->avg_buckets[WRITE][i].valid);
}
#else
static inline void throtl_update_latency_buckets(struct throtl_data *td)
@@ -2258,16 +2269,17 @@ static void throtl_track_latency(struct throtl_data *td, sector_t size,
struct latency_bucket *latency;
int index;
- if (!td || td->limit_index != LIMIT_LOW || op != REQ_OP_READ ||
+ if (!td || td->limit_index != LIMIT_LOW ||
+ !(op == REQ_OP_READ || op == REQ_OP_WRITE) ||
!blk_queue_nonrot(td->queue))
return;
index = request_bucket_index(size);
- latency = get_cpu_ptr(td->latency_buckets);
+ latency = get_cpu_ptr(td->latency_buckets[op]);
latency[index].total_latency += time;
latency[index].samples++;
- put_cpu_ptr(td->latency_buckets);
+ put_cpu_ptr(td->latency_buckets[op]);
}
void blk_throtl_stat_add(struct request *rq, u64 time_ns)
@@ -2286,6 +2298,7 @@ void blk_throtl_bio_endio(struct bio *bio)
unsigned long finish_time;
unsigned long start_time;
unsigned long lat;
+ int rw = bio_data_dir(bio);
tg = bio->bi_cg_private;
if (!tg)
@@ -2314,7 +2327,7 @@ void blk_throtl_bio_endio(struct bio *bio)
bucket = request_bucket_index(
blk_stat_size(&bio->bi_issue_stat));
- threshold = tg->td->avg_buckets[bucket].latency +
+ threshold = tg->td->avg_buckets[rw][bucket].latency +
tg->latency_target;
if (lat > threshold)
tg->bad_bio_cnt++;
@@ -2407,9 +2420,16 @@ int blk_throtl_init(struct request_queue *q)
td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node);
if (!td)
return -ENOMEM;
- td->latency_buckets = __alloc_percpu(sizeof(struct latency_bucket) *
+ td->latency_buckets[READ] = __alloc_percpu(sizeof(struct latency_bucket) *
+ LATENCY_BUCKET_SIZE, __alignof__(u64));
+ if (!td->latency_buckets[READ]) {
+ kfree(td);
+ return -ENOMEM;
+ }
+ td->latency_buckets[WRITE] = __alloc_percpu(sizeof(struct latency_bucket) *
LATENCY_BUCKET_SIZE, __alignof__(u64));
- if (!td->latency_buckets) {
+ if (!td->latency_buckets[WRITE]) {
+ free_percpu(td->latency_buckets[READ]);
kfree(td);
return -ENOMEM;
}
@@ -2428,7 +2448,8 @@ int blk_throtl_init(struct request_queue *q)
/* activate policy */
ret = blkcg_activate_policy(q, &blkcg_policy_throtl);
if (ret) {
- free_percpu(td->latency_buckets);
+ free_percpu(td->latency_buckets[READ]);
+ free_percpu(td->latency_buckets[WRITE]);
kfree(td);
}
return ret;
@@ -2439,7 +2460,8 @@ void blk_throtl_exit(struct request_queue *q)
BUG_ON(!q->td);
throtl_shutdown_wq(q);
blkcg_deactivate_policy(q, &blkcg_policy_throtl);
- free_percpu(q->td->latency_buckets);
+ free_percpu(q->td->latency_buckets[READ]);
+ free_percpu(q->td->latency_buckets[WRITE]);
kfree(q->td);
}
@@ -2457,8 +2479,10 @@ void blk_throtl_register_queue(struct request_queue *q)
} else {
td->throtl_slice = DFL_THROTL_SLICE_HD;
td->filtered_latency = LATENCY_FILTERED_HD;
- for (i = 0; i < LATENCY_BUCKET_SIZE; i++)
- td->avg_buckets[i].latency = DFL_HD_BASELINE_LATENCY;
+ for (i = 0; i < LATENCY_BUCKET_SIZE; i++) {
+ td->avg_buckets[READ][i].latency = DFL_HD_BASELINE_LATENCY;
+ td->avg_buckets[WRITE][i].latency = DFL_HD_BASELINE_LATENCY;
+ }
}
#ifndef CONFIG_BLK_DEV_THROTTLING_LOW
/* if no low limit, use previous default */