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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: Shaohua Li <shli@fb.com>
This commit is contained in:
Shaohua Li 2017-02-10 16:18:09 -08:00
parent e8fd52eec2
commit e33fbb9cc7
3 changed files with 16 additions and 2 deletions
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14
drivers/md/raid5-cache.c
View File

@ -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);
}
}

2
drivers/md/raid5.c
View File

@ -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;

2
drivers/md/raid5.h
View File

@ -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;