Commit e33fbb9c authored by Shaohua Li's avatar Shaohua Li
Browse files

md/raid5-cache: exclude reclaiming stripes in reclaim check 



stripes which are being reclaimed are still accounted into cached
stripes. The reclaim takes time. r5c_do_reclaim isn't aware of the
stripes and does unnecessary stripe reclaim. In practice, I saw one
stripe is reclaimed one time. This will cause bad IO pattern. Fixing
this by excluding the reclaing stripes in the check.

Cc: Song Liu <songliubraving@fb.com>
Signed-off-by: default avatarShaohua Li <shli@fb.com>
parent e8fd52ee

drivers/md/raid5-cache.c

+12 −2
Original line number Diff line number Diff line
@@ -1327,6 +1327,10 @@ static void r5c_flush_stripe(struct r5conf *conf, struct stripe_head *sh) 
	atomic_inc(&conf->active_stripes);

	r5c_make_stripe_write_out(sh);



	if (test_bit(STRIPE_R5C_PARTIAL_STRIPE, &sh->state))

		atomic_inc(&conf->r5c_flushing_partial_stripes);

	else

		atomic_inc(&conf->r5c_flushing_full_stripes);

	raid5_release_stripe(sh);

}
@@ -1369,12 +1373,16 @@ static void r5c_do_reclaim(struct r5conf *conf) 
	unsigned long flags;

	int total_cached;

	int stripes_to_flush;

	int flushing_partial, flushing_full;



	if (!r5c_is_writeback(log))

		return;



	flushing_partial = atomic_read(&conf->r5c_flushing_partial_stripes);

	flushing_full = atomic_read(&conf->r5c_flushing_full_stripes);

	total_cached = atomic_read(&conf->r5c_cached_partial_stripes) +

		atomic_read(&conf->r5c_cached_full_stripes);

		atomic_read(&conf->r5c_cached_full_stripes) -

		flushing_full - flushing_partial;



	if (total_cached > conf->min_nr_stripes * 3 / 4 ||

	    atomic_read(&conf->empty_inactive_list_nr) > 0)
@@ -1384,7 +1392,7 @@ static void r5c_do_reclaim(struct r5conf *conf) 
		 */

		stripes_to_flush = R5C_RECLAIM_STRIPE_GROUP;

	else if (total_cached > conf->min_nr_stripes * 1 / 2 ||

		 atomic_read(&conf->r5c_cached_full_stripes) >

		 atomic_read(&conf->r5c_cached_full_stripes) - flushing_full >

		 R5C_FULL_STRIPE_FLUSH_BATCH)

		/*

		 * if stripe cache pressure moderate, or if there is many full
@@ -2601,11 +2609,13 @@ void r5c_finish_stripe_write_out(struct r5conf *conf, 


	if (test_and_clear_bit(STRIPE_R5C_PARTIAL_STRIPE, &sh->state)) {

		BUG_ON(atomic_read(&conf->r5c_cached_partial_stripes) == 0);

		atomic_dec(&conf->r5c_flushing_partial_stripes);

		atomic_dec(&conf->r5c_cached_partial_stripes);

	}



	if (test_and_clear_bit(STRIPE_R5C_FULL_STRIPE, &sh->state)) {

		BUG_ON(atomic_read(&conf->r5c_cached_full_stripes) == 0);

		atomic_dec(&conf->r5c_flushing_full_stripes);

		atomic_dec(&conf->r5c_cached_full_stripes);

	}

}

drivers/md/raid5.c

+2 −0
Original line number Diff line number Diff line
@@ -6838,6 +6838,8 @@ static struct r5conf *setup_conf(struct mddev *mddev) 
	INIT_LIST_HEAD(&conf->r5c_full_stripe_list);

	atomic_set(&conf->r5c_cached_partial_stripes, 0);

	INIT_LIST_HEAD(&conf->r5c_partial_stripe_list);

	atomic_set(&conf->r5c_flushing_full_stripes, 0);

	atomic_set(&conf->r5c_flushing_partial_stripes, 0);



	conf->level = mddev->new_level;

	conf->chunk_sectors = mddev->new_chunk_sectors;

drivers/md/raid5.h

+2 −0
Original line number Diff line number Diff line
@@ -663,6 +663,8 @@ struct r5conf { 
	struct list_head	r5c_full_stripe_list;

	atomic_t		r5c_cached_partial_stripes;

	struct list_head	r5c_partial_stripe_list;

	atomic_t		r5c_flushing_full_stripes;

	atomic_t		r5c_flushing_partial_stripes;



	atomic_t		empty_inactive_list_nr;

	struct llist_head	released_stripes;

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