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md: improve io stats accounting

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Use generic io accounting functions to manage io stats. There was an
attempt to do this earlier in commit 18c0b223cf ("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 74672d069b
("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.

Acked-by: Guoqing Jiang <guoqing.jiang@cloud.ionos.com>
Signed-off-by: Artur Paszkiewicz <artur.paszkiewicz@intel.com>
Signed-off-by: Song Liu <songliubraving@fb.com>
This commit is contained in:
Artur Paszkiewicz 2020-07-03 11:13:09 +02:00 committed by Song Liu
parent 9a5a85972c
commit 41d2d848e5
2 changed files with 46 additions and 12 deletions
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57
drivers/md/md.c
View File

@ -463,12 +463,33 @@ check_suspended:
}
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 (mddev == NULL || mddev->pers == NULL) {
bio_io_error(bio);
@ -489,21 +510,27 @@ 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;
}
@ -5546,6 +5573,7 @@ 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);
}
@ -5641,6 +5669,11 @@ 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)

1
drivers/md/md.h
View File

@ -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