Use generic io accounting functions to manage io stats. There was an
attempt to do this earlier in commit 18c0b223cf99 ("md: use generic io
stats accounting functions to simplify io stat accounting"), but it did
not include a call to generic_end_io_acct() and caused issues with
tracking in-flight IOs, so it was later removed in commit 74672d069b29
("md: fix md io stats accounting broken").
This patch attempts to fix this by using both disk_start_io_acct() and
disk_end_io_acct(). To make it possible, a struct md_io is allocated for
every new md bio, which includes the io start_time. A new mempool is
introduced for this purpose. We override bio->bi_end_io with our own
callback and call disk_start_io_acct() before passing the bio to
md_handle_request(). When it completes, we call disk_end_io_acct() and
the original bi_end_io callback.
This adds correct statistics about in-flight IOs and IO processing time,
interpreted e.g. in iostat as await, svctm, aqu-sz and %util.
It also fixes a situation where too many IOs where reported if a bio was
re-submitted to the mddev, because io accounting is now performed only
on newly arriving bios.
Signed-off-by: Artur Paszkiewicz <artur.paszkiewicz@xxxxxxxxx>
---
v4:
- Use disk_{start,end}_io_acct() instead of bio_{start,end}_io_acct() to
pass mddev->gendisk directly, not bio->bi_disk which gets modified by
some personalities.
v3:
- Use bio_start_io_acct() return value for md_io->start_time (thanks
Guoqing!)
v2:
- Just override the bi_end_io without having to clone the original bio.
- Rebased onto latest md-next.
drivers/md/md.c | 57 ++++++++++++++++++++++++++++++++++++++-----------
drivers/md/md.h | 1 +
2 files changed, 46 insertions(+), 12 deletions(-)
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 8bb69c61afe0..63aeebd9266b 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -463,12 +463,33 @@ void md_handle_request(struct mddev *mddev, struct bio *bio)
}
EXPORT_SYMBOL(md_handle_request);
+struct md_io {
+ struct mddev *mddev;
+ bio_end_io_t *orig_bi_end_io;
+ void *orig_bi_private;
+ unsigned long start_time;
+};
+
+static void md_end_io(struct bio *bio)
+{
+ struct md_io *md_io = bio->bi_private;
+ struct mddev *mddev = md_io->mddev;
+
+ disk_end_io_acct(mddev->gendisk, bio_op(bio), md_io->start_time);
+
+ bio->bi_end_io = md_io->orig_bi_end_io;
+ bio->bi_private = md_io->orig_bi_private;
+
+ mempool_free(md_io, &mddev->md_io_pool);
+
+ if (bio->bi_end_io)
+ bio->bi_end_io(bio);
+}
+
static blk_qc_t md_submit_bio(struct bio *bio)
{
const int rw = bio_data_dir(bio);
- const int sgrp = op_stat_group(bio_op(bio));
struct mddev *mddev = bio->bi_disk->private_data;
- unsigned int sectors;
if (unlikely(test_bit(MD_BROKEN, &mddev->flags)) && (rw == WRITE)) {
bio_io_error(bio);
@@ -488,21 +509,27 @@ static blk_qc_t md_submit_bio(struct bio *bio)
return BLK_QC_T_NONE;
}
- /*
- * save the sectors now since our bio can
- * go away inside make_request
- */
- sectors = bio_sectors(bio);
+ if (bio->bi_end_io != md_end_io) {
+ struct md_io *md_io;
+
+ md_io = mempool_alloc(&mddev->md_io_pool, GFP_NOIO);
+ md_io->mddev = mddev;
+ md_io->orig_bi_end_io = bio->bi_end_io;
+ md_io->orig_bi_private = bio->bi_private;
+
+ bio->bi_end_io = md_end_io;
+ bio->bi_private = md_io;
+
+ md_io->start_time = disk_start_io_acct(mddev->gendisk,
+ bio_sectors(bio),
+ bio_op(bio));
+ }
+
/* bio could be mergeable after passing to underlayer */
bio->bi_opf &= ~REQ_NOMERGE;
md_handle_request(mddev, bio);
- part_stat_lock();
- part_stat_inc(&mddev->gendisk->part0, ios[sgrp]);
- part_stat_add(&mddev->gendisk->part0, sectors[sgrp], sectors);
- part_stat_unlock();
-
return BLK_QC_T_NONE;
}
@@ -5545,6 +5572,7 @@ static void md_free(struct kobject *ko)
bioset_exit(&mddev->bio_set);
bioset_exit(&mddev->sync_set);
+ mempool_exit(&mddev->md_io_pool);
kfree(mddev);
}
@@ -5640,6 +5668,11 @@ static int md_alloc(dev_t dev, char *name)
*/
mddev->hold_active = UNTIL_STOP;
+ error = mempool_init_kmalloc_pool(&mddev->md_io_pool, BIO_POOL_SIZE,
+ sizeof(struct md_io));
+ if (error)
+ goto abort;
+
error = -ENOMEM;
mddev->queue = blk_alloc_queue(NUMA_NO_NODE);
if (!mddev->queue)
diff --git a/drivers/md/md.h b/drivers/md/md.h
index 612814d07d35..c26fa8bd41e7 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -481,6 +481,7 @@ struct mddev {
struct bio_set sync_set; /* for sync operations like
* metadata and bitmap writes
*/
+ mempool_t md_io_pool;
/* Generic flush handling.
* The last to finish preflush schedules a worker to submit
--
2.26.0
