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From: Coly Li <colyli@suse.de>
To: linux-bcache@vger.kernel.org
Cc: linux-block@vger.kernel.org, Coly Li <colyli@suse.de>
Subject: [RFC PATCH 15/16] bcache: avoid extra memory allocation from mempool c->fill_iter
Date: Sun,  5 Jul 2020 23:56:00 +0800
Message-ID: <20200705155601.5404-16-colyli@suse.de> (raw)
In-Reply-To: <20200705155601.5404-1-colyli@suse.de>

Mempool c->fill_iter is used to allocate memory for struct btree_iter in
bch_btree_node_read_done() to iterate all keys of a read-in btree node.

The allocation size is defined in bch_cache_set_alloc() by,
  mempool_init_kmalloc_pool(&c->fill_iter, 1, iter_size))
where iter_size is defined by a calculation,
  (sb->bucket_size / sb->block_size + 1) * sizeof(struct btree_iter_set)

For 16bit width bucket_size the calculation is OK, but now the bucket
size is extended to 32bit, the bucket size can be 2GB. By the above
calculation, iter_size can be 2048 pages (order 11 is still accepted by
buddy allocator).

But the actual size holds the bkeys in meta data bucket is limited to
meta_bucket_pages() already, which is 16MB. By the above calculation,
if replace sb->bucket_size by meta_bucket_pages() * PAGE_SECTORS, the
result is 16 pages. This is the size large enough for the mempool
allocation to struct btree_iter.

Therefore in worst case every time mempool c->fill_iter allocates, at
most 4080 pages are wasted and won't be used. Therefore this patch uses
meta_bucket_pages() * PAGE_SECTORS to calculate the iter size in
bch_cache_set_alloc(), to avoid extra memory allocation from mempool
c->fill_iter.

Signed-off-by: Coly Li <colyli@suse.de>
---
 drivers/md/bcache/super.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 79bf6d9383bd..6766d426e933 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -1901,7 +1901,7 @@ struct cache_set *bch_cache_set_alloc(struct cache_sb *sb)
 	INIT_LIST_HEAD(&c->btree_cache_freed);
 	INIT_LIST_HEAD(&c->data_buckets);
 
-	iter_size = (sb->bucket_size / sb->block_size + 1) *
+	iter_size = ((meta_bucket_pages(sb) * PAGE_SECTORS) / sb->block_size + 1) *
 		sizeof(struct btree_iter_set);
 
 	c->devices = kcalloc(c->nr_uuids, sizeof(void *), GFP_KERNEL);
-- 
2.26.2

  parent reply index

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-05 15:55 [RFC PATCH 00/16] bcache: extend bucket size to 32bit width Coly Li
2020-07-05 15:55 ` [RFC PATCH 01/16] bcache: add comments to mark member offset of struct cache_sb_disk Coly Li
2020-07-05 15:55 ` [RFC PATCH 02/16] bcache: add read_super_basic() to read major part of super block Coly Li
2020-07-05 15:55   ` Coly Li
2020-07-05 15:55 ` [RFC PATCH 03/16] bcache: add more accurate error information in read_super_basic() Coly Li
2020-07-05 15:55   ` Coly Li
2020-07-05 15:55 ` [RFC PATCH 04/16] bcache: disassemble the big if() checks in bch_cache_set_alloc() Coly Li
2020-07-05 15:55   ` Coly Li
2020-07-05 15:55 ` [RFC PATCH 05/16] bcache: fix super block seq numbers comparision in register_cache_set() Coly Li
2020-07-05 15:55 ` [RFC PATCH 06/16] bcache: increase super block version for cache device and backing device Coly Li
2020-07-05 15:55 ` [RFC PATCH 07/16] bcache: move bucket related code into read_super_basic() Coly Li
2020-07-05 15:55 ` [RFC PATCH 08/16] bcache: struct cache_sb is only for in-memory super block now Coly Li
2020-07-05 15:55 ` [RFC PATCH 09/16] bcache: introduce meta_bucket_pages() related helper routines Coly Li
2020-07-05 15:55   ` Coly Li
2020-07-05 15:55 ` [RFC PATCH 10/16] bcache: handle c->uuids properly for bucket size > 8MB Coly Li
2020-07-05 15:55 ` [RFC PATCH 11/16] bcache: handle cache prio_buckets and disk_buckets " Coly Li
2020-07-05 15:55 ` [RFC PATCH 12/16] bcache: handle cache set verify_ondisk " Coly Li
2020-07-05 15:55   ` Coly Li
2020-07-05 15:55 ` [RFC PATCH 13/16] bcache: handle btree node memory allocation " Coly Li
2020-07-05 15:55   ` Coly Li
2020-07-05 15:55 ` [RFC PATCH 14/16] bcache: add bucket_size_hi into struct cache_sb_disk for large bucket Coly Li
2020-07-05 15:56 ` Coly Li [this message]
2020-07-05 15:56 ` [RFC PATCH 16/16] bcache: avoid extra memory consumption in struct bbio for large bucket size Coly Li

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