Commit 41d2d848 authored by Artur Paszkiewicz's avatar Artur Paszkiewicz Committed by Song Liu
Browse files

md: improve io stats accounting 



Use generic io accounting functions to manage io stats. There was an
attempt to do this earlier in commit 18c0b223 ("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 74672d06
("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: default avatarGuoqing Jiang <guoqing.jiang@cloud.ionos.com>
Signed-off-by: default avatarArtur Paszkiewicz <artur.paszkiewicz@intel.com>
Signed-off-by: default avatarSong Liu <songliubraving@fb.com>
parent 9a5a8597

drivers/md/md.c

+45 −12
Original line number Diff line number Diff line
@@ -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)

drivers/md/md.h

+1 −0
Original line number Diff line number Diff line
@@ -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

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