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Message-Id: <25f7593a0350e07997fc31d1317218ffeec4f6bf.1556609582.git.asml.silence@gmail.com>
Date: Tue, 30 Apr 2019 10:34:17 +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 5/7] blk-mq: Precalculate hybrid polling time
From: Pavel Begunkov <asml.silence@...il.com>
Calculation of sleep time for adaptive hybrid polling on per-request
basis could become time consuming in the future.
Precalculate it once per statistics gathering round.
Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
---
block/blk-core.c | 5 ++++-
block/blk-mq-debugfs.c | 4 ++--
block/blk-mq.c | 39 ++++++++++++++++++++++-----------------
include/linux/blkdev.h | 8 +++++++-
4 files changed, 35 insertions(+), 21 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index a55389ba8779..daadce545e43 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -474,7 +474,7 @@ static void blk_timeout_work(struct work_struct *work)
struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
{
struct request_queue *q;
- int ret;
+ int ret, bucket;
q = kmem_cache_alloc_node(blk_requestq_cachep,
gfp_mask | __GFP_ZERO, node_id);
@@ -536,6 +536,9 @@ struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
if (blkcg_init_queue(q))
goto fail_ref;
+ for (bucket = 0; bucket < BLK_MQ_POLL_STATS_BKTS; bucket++)
+ q->poll_info[bucket].sleep_ns = 0;
+
return q;
fail_ref:
diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
index b62bd4468db3..ab55446cb570 100644
--- a/block/blk-mq-debugfs.c
+++ b/block/blk-mq-debugfs.c
@@ -44,11 +44,11 @@ static int queue_poll_stat_show(void *data, struct seq_file *m)
for (bucket = 0; bucket < BLK_MQ_POLL_STATS_BKTS/2; bucket++) {
seq_printf(m, "read (%d Bytes): ", 1 << (9+bucket));
- print_stat(m, &q->poll_stat[2*bucket]);
+ print_stat(m, &q->poll_info[2*bucket].stat);
seq_puts(m, "\n");
seq_printf(m, "write (%d Bytes): ", 1 << (9+bucket));
- print_stat(m, &q->poll_stat[2*bucket+1]);
+ print_stat(m, &q->poll_info[2*bucket+1].stat);
seq_puts(m, "\n");
}
return 0;
diff --git a/block/blk-mq.c b/block/blk-mq.c
index cc3f73e4e01c..4e54a004e345 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -3312,14 +3312,32 @@ static void blk_mq_poll_stats_start(struct request_queue *q)
blk_stat_activate_msecs(q->poll_cb, 100);
}
+static void blk_mq_update_poll_info(struct poll_info *pi,
+ struct blk_rq_stat *stat)
+{
+ u64 sleep_ns;
+
+ if (!stat->nr_samples)
+ sleep_ns = 0;
+ else
+ sleep_ns = (stat->mean + 1) / 2;
+
+ pi->stat = *stat;
+ pi->sleep_ns = sleep_ns;
+}
+
static void blk_mq_poll_stats_fn(struct blk_stat_callback *cb)
{
struct request_queue *q = cb->data;
int bucket;
for (bucket = 0; bucket < BLK_MQ_POLL_STATS_BKTS; bucket++) {
- if (cb->stat[bucket].nr_samples)
- q->poll_stat[bucket] = cb->stat[bucket];
+ if (cb->stat[bucket].nr_samples) {
+ struct poll_info *pi = &q->poll_info[bucket];
+ struct blk_rq_stat *stat = &cb->stat[bucket];
+
+ blk_mq_update_poll_info(pi, stat);
+ }
}
}
@@ -3327,7 +3345,6 @@ static unsigned long blk_mq_poll_nsecs(struct request_queue *q,
struct blk_mq_hw_ctx *hctx,
struct request *rq)
{
- unsigned long ret = 0;
int bucket;
/*
@@ -3337,23 +3354,11 @@ static unsigned long blk_mq_poll_nsecs(struct request_queue *q,
if (!blk_poll_stats_enable(q))
return 0;
- /*
- * As an optimistic guess, use half of the mean service time
- * for this type of request. We can (and should) make this smarter.
- * For instance, if the completion latencies are tight, we can
- * get closer than just half the mean. This is especially
- * important on devices where the completion latencies are longer
- * than ~10 usec. We do use the stats for the relevant IO size
- * if available which does lead to better estimates.
- */
bucket = blk_mq_poll_stats_bkt(rq);
if (bucket < 0)
- return ret;
-
- if (q->poll_stat[bucket].nr_samples)
- ret = (q->poll_stat[bucket].mean + 1) / 2;
+ return 0;
- return ret;
+ return q->poll_info[bucket].sleep_ns;
}
static bool blk_mq_poll_hybrid_sleep(struct request_queue *q,
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 317ab30d2904..40c77935fd61 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -385,6 +385,12 @@ static inline int blkdev_reset_zones_ioctl(struct block_device *bdev,
#endif /* CONFIG_BLK_DEV_ZONED */
+struct poll_info
+{
+ struct blk_rq_stat stat;
+ u64 sleep_ns;
+};
+
struct request_queue {
/*
* Together with queue_head for cacheline sharing
@@ -477,7 +483,7 @@ struct request_queue {
int poll_nsec;
struct blk_stat_callback *poll_cb;
- struct blk_rq_stat poll_stat[BLK_MQ_POLL_STATS_BKTS];
+ struct poll_info poll_info[BLK_MQ_POLL_STATS_BKTS];
struct timer_list timeout;
struct work_struct timeout_work;
--
2.21.0
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