Commit 95b88f4d authored by Mikulas Patocka's avatar Mikulas Patocka Committed by Mike Snitzer
Browse files

dm writecache: pause writeback if cache full and origin being written directly 



Implementation reuses dm_io_tracker, that until now was only used by
dm-cache, to track if any writes were issued directly to the origin
(due to cache being full) within the last second. If so writeback is
paused for a second.

This change improves performance for when the cache is full and IO is
issued directly to the origin device (rather than through the cache).

Depends-on: d53f1faf ("dm writecache: do direct write if the cache is full")
Suggested-by: default avatarJoe Thornber <ejt@redhat.com>
Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
parent dc4fa29f

drivers/md/dm-writecache.c

+20 −1
Original line number Diff line number Diff line
@@ -15,6 +15,8 @@ 
#include <linux/dax.h>

#include <linux/pfn_t.h>

#include <linux/libnvdimm.h>

#include <linux/delay.h>

#include "dm-io-tracker.h"



#define DM_MSG_PREFIX "writecache"
@@ -183,6 +185,8 @@ struct dm_writecache { 
	struct work_struct writeback_work;

	struct work_struct flush_work;



	struct dm_io_tracker iot;



	struct dm_io_client *dm_io;



	raw_spinlock_t endio_list_lock;
@@ -1466,6 +1470,10 @@ static int writecache_map(struct dm_target *ti, struct bio *bio) 
	}



unlock_remap_origin:

	if (bio_data_dir(bio) != READ) {

		dm_iot_io_begin(&wc->iot, 1);

		bio->bi_private = (void *)2;

	}

	bio_set_dev(bio, wc->dev->bdev);

	wc_unlock(wc);

	return DM_MAPIO_REMAPPED;
@@ -1496,11 +1504,13 @@ static int writecache_end_io(struct dm_target *ti, struct bio *bio, blk_status_t 
{

	struct dm_writecache *wc = ti->private;



	if (bio->bi_private != NULL) {

	if (bio->bi_private == (void *)1) {

		int dir = bio_data_dir(bio);

		if (atomic_dec_and_test(&wc->bio_in_progress[dir]))

			if (unlikely(waitqueue_active(&wc->bio_in_progress_wait[dir])))

				wake_up(&wc->bio_in_progress_wait[dir]);

	} else if (bio->bi_private == (void *)2) {

		dm_iot_io_end(&wc->iot, 1);

	}

	return 0;

}
@@ -1827,6 +1837,13 @@ static void writecache_writeback(struct work_struct *work) 
		dm_kcopyd_client_flush(wc->dm_kcopyd);

	}



	if (!wc->writeback_all && !dm_suspended(wc->ti)) {

		while (!dm_iot_idle_for(&wc->iot, HZ)) {

			cond_resched();

			msleep(1000);

		}

	}



	wc_lock(wc);

restart:

	if (writecache_has_error(wc)) {
@@ -2140,6 +2157,8 @@ static int writecache_ctr(struct dm_target *ti, unsigned argc, char **argv) 
	INIT_WORK(&wc->writeback_work, writecache_writeback);

	INIT_WORK(&wc->flush_work, writecache_flush_work);



	dm_iot_init(&wc->iot);



	raw_spin_lock_init(&wc->endio_list_lock);

	INIT_LIST_HEAD(&wc->endio_list);

	wc->endio_thread = kthread_create(writecache_endio_thread, wc, "writecache_endio");