On 7/15/20 4:30 PM, colyli@xxxxxxx wrote:
From: Coly Li <colyli@xxxxxxx>
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@xxxxxxx>
---
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 e0da52f8e8c9..90494c7dead8 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -1908,7 +1908,7 @@ 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);
Reviewed-by: Hannes Reinecke <hare@xxxxxxx>
Cheers,
Hannes
--
Dr. Hannes Reinecke Teamlead Storage & Networking
hare@xxxxxxx +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer
