Re: [PATCH -next 3/3] block: update nsecs[] in part_get_stat()
From: yukuai (C)
Date: Fri Apr 08 2022 - 02:52:31 EST
在 2022/04/01 11:42, yukuai (C) 写道:
在 2022/03/17 19:26, Yu Kuai 写道:
commit 86d7331299fd("block: update io_ticks when io hang") fixed that
%util will be zero for iostat when io is hanged, however, avgqu-sz is
still zero while it represents the number of io that are hunged. On the
other hand, for some slow device, if an io is started before and done
after diskstats is read, the avgqu-sz will be miscalculated.
To fix the problem, update 'nsecs[]' when part_stat_show() or
diskstats_show() is called. In order to do that, add 'stat_time' in
struct block_device and 'rq_stat_time' in struct request to record the
time. And during iteration, update 'nsecs[]' for each inflight request.
Friendly ping... Does anyone have any suggestions on this apporch ?
friendlig ping ...
Thanks,
Kuai
Fixes: 5b18b5a73760 ("block: delete part_round_stats and switch to
less precise counting")
Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
---
block/bdev.c | 2 ++
block/blk-mq.c | 63 ++++++++++++++++++++++++++++++++++++++-
block/blk-mq.h | 2 ++
block/genhd.c | 25 ++++++++++++++--
include/linux/blk-mq.h | 2 ++
include/linux/blk_types.h | 5 ++++
6 files changed, 95 insertions(+), 4 deletions(-)
diff --git a/block/bdev.c b/block/bdev.c
index 13de871fa816..5dced478f190 100644
--- a/block/bdev.c
+++ b/block/bdev.c
@@ -487,9 +487,11 @@ struct block_device *bdev_alloc(struct gendisk
*disk, u8 partno)
bdev = I_BDEV(inode);
mutex_init(&bdev->bd_fsfreeze_mutex);
spin_lock_init(&bdev->bd_size_lock);
+ spin_lock_init(&bdev->bd_stat_lock);
bdev->bd_partno = partno;
bdev->bd_inode = inode;
bdev->bd_queue = disk->queue;
+ bdev->stat_time = 0;
bdev->bd_stats = alloc_percpu(struct disk_stats);
if (!bdev->bd_stats) {
iput(inode);
diff --git a/block/blk-mq.c b/block/blk-mq.c
index c33fb378b168..7a14d4058b14 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -149,6 +149,48 @@ unsigned int blk_mq_in_flight(struct
request_queue *q,
return mi.inflight[0] + mi.inflight[1];
}
+static bool blk_mq_check_inflight_stat(struct request *rq, void *priv,
+ bool reserved)
+{
+ struct mq_inflight *mi = priv;
+
+ if ((!mi->part->bd_partno || rq->part == mi->part) &&
+ blk_mq_rq_state(rq) == MQ_RQ_IN_FLIGHT) {
+ u64 stat_time;
+
+ mi->inflight[rq_data_dir(rq)]++;
+ if (!rq->part)
+ return true;
+
+ stat_time = READ_ONCE(rq->stat_time_ns);
+ /*
+ * This might fail if 'req->stat_time_ns' happen to be updated
+ * in blk_account_io_done().
+ */
+ if (likely(cmpxchg(&rq->stat_time_ns, stat_time,
+ rq->part->stat_time) == stat_time)) {
+ int sgrp = op_stat_group(req_op(rq));
+ u64 duation = stat_time ?
+ rq->part->stat_time - stat_time :
+ rq->part->stat_time - rq->start_time_ns;
+
+ part_stat_add(rq->part, nsecs[sgrp], duation);
+ }
+ }
+
+ return true;
+}
+
+unsigned int blk_mq_in_flight_stat(struct request_queue *q,
+ struct block_device *part)
+{
+ struct mq_inflight mi = { .part = part };
+
+ blk_mq_queue_tag_busy_iter(q, blk_mq_check_inflight_stat, &mi);
+
+ return mi.inflight[0] + mi.inflight[1];
+}
+
void blk_mq_in_flight_rw(struct request_queue *q, struct
block_device *part,
unsigned int inflight[2])
{
@@ -368,6 +410,7 @@ static struct request *blk_mq_rq_ctx_init(struct
blk_mq_alloc_data *data,
rq->start_time_ns = ktime_get_ns();
else
rq->start_time_ns = 0;
+ rq->stat_time_ns = 0;
rq->part = NULL;
#ifdef CONFIG_BLK_RQ_ALLOC_TIME
rq->alloc_time_ns = alloc_time_ns;
@@ -874,7 +917,25 @@ static void __blk_account_io_done(struct request
*req, u64 now)
part_stat_lock();
update_io_ticks(req->part, jiffies, true);
part_stat_inc(req->part, ios[sgrp]);
- part_stat_add(req->part, nsecs[sgrp], now - req->start_time_ns);
+
+ if (queue_is_mq(req->q)) {
+ u64 stat_time = READ_ONCE(req->stat_time_ns);
+
+ /*
+ * This might fail if 'req->stat_time_ns' happen to be updated
+ * in part_get_stat().
+ */
+ if (likely(cmpxchg(&req->stat_time_ns, stat_time, now) ==
+ stat_time)) {
+ u64 duation = stat_time ? now - stat_time :
+ now - req->start_time_ns;
+
+ part_stat_add(req->part, nsecs[sgrp], duation);
+ }
+ } else {
+ part_stat_add(req->part, nsecs[sgrp],
+ now - req->part->stat_time);
+ }
part_stat_unlock();
}
diff --git a/block/blk-mq.h b/block/blk-mq.h
index 7d1acf8e1e51..37941f5f1d08 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -189,6 +189,8 @@ static inline bool blk_mq_hw_queue_mapped(struct
blk_mq_hw_ctx *hctx)
unsigned int blk_mq_in_flight(struct request_queue *q,
struct block_device *part);
+unsigned int blk_mq_in_flight_stat(struct request_queue *q,
+ struct block_device *part);
void blk_mq_in_flight_rw(struct request_queue *q, struct
block_device *part,
unsigned int inflight[2]);
diff --git a/block/genhd.c b/block/genhd.c
index f2c7de2e7ca9..31603c7aff49 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -953,6 +953,19 @@ ssize_t part_size_show(struct device *dev,
return sprintf(buf, "%llu\n", bdev_nr_sectors(dev_to_bdev(dev)));
}
+static void part_set_stat_time(struct block_device *part)
+{
+ u64 now = ktime_get_ns();
+
+again:
+ part->stat_time = now;
+
+ if (part->bd_partno) {
+ part = bdev_whole(part);
+ goto again;
+ }
+}
+
static unsigned int part_get_stat(struct block_device *bdev,
struct disk_stats *stat)
@@ -960,10 +973,16 @@ static unsigned int part_get_stat(struct
block_device *bdev,
struct request_queue *q = bdev_get_queue(bdev);
unsigned int inflight;
- if (queue_is_mq(q))
- inflight = blk_mq_in_flight(q, bdev);
- else
+ if (queue_is_mq(q)) {
+ spin_lock(&bdev->bd_stat_lock);
+ part_stat_lock();
+ part_set_stat_time(bdev);
+ inflight = blk_mq_in_flight_stat(q, bdev);
+ part_stat_unlock();
+ spin_unlock(&bdev->bd_stat_lock);
+ } else {
inflight = part_in_flight(bdev);
+ }
if (inflight) {
part_stat_lock();
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index e512da636e0f..e98f07d1741c 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -108,6 +108,8 @@ struct request {
u64 start_time_ns;
/* Time that I/O was submitted to the device. */
u64 io_start_time_ns;
+ /* Time that I/O was accounted in part_get_stat() */
+ u64 stat_time_ns;
#ifdef CONFIG_BLK_WBT
unsigned short wbt_flags;
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index c6ed4a559e6a..5cd399b5670d 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -65,6 +65,11 @@ struct block_device {
struct super_block *bd_fsfreeze_sb;
struct partition_meta_info *bd_meta_info;
+
+ /* Prevent part_get_stat() to be called concurrently */
+ spinlock_t bd_stat_lock;
+ /* Will be set when part_stat_show() or diskstats_show() is
called */
+ u64 stat_time;
#ifdef CONFIG_FAIL_MAKE_REQUEST
bool bd_make_it_fail;
#endif