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Commit 6ded34d1 authored by Kent Overstreet's avatar Kent Overstreet
Browse files

bcache: Improve lazy sorting 



The old lazy sorting code was kind of hacky - rewrite in a way that
mathematically makes more sense; the idea is that the size of the sets
of keys in a btree node should increase by a more or less fixed ratio
from smallest to biggest.

Signed-off-by: default avatarKent Overstreet <koverstreet@google.com>
parent 85b1492e

drivers/md/bcache/bcache.h

+1 −0
Original line number Diff line number Diff line
@@ -828,6 +828,7 @@ struct cache_set { 
	 */

	struct mutex		sort_lock;

	struct bset		*sort;

	unsigned		sort_crit_factor;



	/* List of buckets we're currently writing data to */

	struct list_head	data_buckets;

drivers/md/bcache/bset.c

+23 −17
Original line number Diff line number Diff line
@@ -1092,33 +1092,39 @@ void bch_btree_sort_into(struct btree *b, struct btree *new) 
	new->sets->size = 0;

}



#define SORT_CRIT	(4096 / sizeof(uint64_t))



void bch_btree_sort_lazy(struct btree *b)

{

	if (b->nsets) {

		unsigned i, j, keys = 0, total;



		for (i = 0; i <= b->nsets; i++)

			keys += b->sets[i].data->keys;

	unsigned crit = SORT_CRIT;

	int i;



		total = keys;

	/* Don't sort if nothing to do */

	if (!b->nsets)

		goto out;



		for (j = 0; j < b->nsets; j++) {

			if (keys * 2 < total ||

			    keys < 1000) {

				bch_btree_sort_partial(b, j);

	/* If not a leaf node, always sort */

	if (b->level) {

		bch_btree_sort(b);

		return;

	}



			keys -= b->sets[j].data->keys;

	for (i = b->nsets - 1; i >= 0; --i) {

		crit *= b->c->sort_crit_factor;



		if (b->sets[i].data->keys < crit) {

			bch_btree_sort_partial(b, i);

			return;

		}

	}



		/* Must sort if b->nsets == 3 or we'll overflow */

		if (b->nsets >= (MAX_BSETS - 1) - b->level) {

	/* Sort if we'd overflow */

	if (b->nsets + 1 == MAX_BSETS) {

		bch_btree_sort(b);

		return;

	}

	}



out:

	bset_build_written_tree(b);

}

drivers/md/bcache/super.c

+2 −0
Original line number Diff line number Diff line
@@ -1375,6 +1375,8 @@ struct cache_set *bch_cache_set_alloc(struct cache_sb *sb) 
		c->btree_pages = max_t(int, c->btree_pages / 4,

				       BTREE_MAX_PAGES);



	c->sort_crit_factor = int_sqrt(c->btree_pages);



	mutex_init(&c->bucket_lock);

	mutex_init(&c->sort_lock);

	spin_lock_init(&c->sort_time_lock);