From 4e4d4e0962262c97ba4580716d11623384effdfd Mon Sep 17 00:00:00 2001 From: Coly Li Date: Sat, 25 Jul 2020 20:00:38 +0800 Subject: bcache: avoid extra memory consumption in struct bbio for large bucket size Bcache uses struct bbio to do I/Os for meta data pages like uuids, disk_buckets, prio_buckets, and btree nodes. Example writing a btree node onto cache device, the process is, - Allocate a struct bbio from mempool c->bio_meta. - Inside struct bbio embedded a struct bio, initialize bi_inline_vecs for this embedded bio. - Call bch_bio_map() to map each meta data page to each bv from the inlined bi_io_vec table. - Call bch_submit_bbio() to submit the bio into underlying block layer. - When the I/O completed, only release the struct bbio, don't touch the reference counter of the meta data pages. The struct bbio is defined as, 738 struct bbio { 739 unsigned int submit_time_us; [snipped] 748 struct bio bio; 749 }; Because struct bio is embedded at the end of struct bbio, therefore the actual size of struct bbio is sizeof(struct bio) + size of the embedded bio->bi_inline_vecs. Now all the meta data bucket size are limited to meta_bucket_pages(), if the bucket size is large than meta_bucket_pages()*PAGE_SECTORS, rested space in the bucket is unused. Therefore the most used space in meta bucket is (1<bio_meta as, mempool_init_kmalloc_pool(&c->bio_meta, 2, sizeof(struct bbio) + sizeof(struct bio_vec) * bucket_pages(c)) It is too large, neither the Linux buddy allocator cannot allocate so much continuous pages, nor the extra allocated pages are wasted. This patch replace bucket_pages() to meta_bucket_pages() in two places, - In bch_cache_set_alloc(), when initialize mempool c->bio_meta, uses sizeof(struct bbio) + sizeof(struct bio_vec) * bucket_pages(c) to set the allocating object size. - In bch_bbio_alloc(), when calling bio_init() to set inline bvec talbe bi_inline_bvecs, uses meta_bucket_pages() to indicate number of the inline bio vencs number. Now the maximum size of embedded bio inside struct bbio exactly matches the limit of meta_bucket_pages(), no extra page wasted. Signed-off-by: Coly Li Reviewed-by: Hannes Reinecke Signed-off-by: Jens Axboe --- drivers/md/bcache/io.c | 2 +- drivers/md/bcache/super.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) (limited to 'drivers/md') diff --git a/drivers/md/bcache/io.c b/drivers/md/bcache/io.c index b25ee33b0d0b..a14a445618b4 100644 --- a/drivers/md/bcache/io.c +++ b/drivers/md/bcache/io.c @@ -26,7 +26,7 @@ struct bio *bch_bbio_alloc(struct cache_set *c) struct bbio *b = mempool_alloc(&c->bio_meta, GFP_NOIO); struct bio *bio = &b->bio; - bio_init(bio, bio->bi_inline_vecs, bucket_pages(c)); + bio_init(bio, bio->bi_inline_vecs, meta_bucket_pages(&c->sb)); return bio; } diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c index c6b6276cada8..a46698f08483 100644 --- a/drivers/md/bcache/super.c +++ b/drivers/md/bcache/super.c @@ -1928,7 +1928,7 @@ struct cache_set *bch_cache_set_alloc(struct cache_sb *sb) if (mempool_init_kmalloc_pool(&c->bio_meta, 2, sizeof(struct bbio) + - sizeof(struct bio_vec) * bucket_pages(c))) + sizeof(struct bio_vec) * meta_bucket_pages(&c->sb))) goto err; if (mempool_init_kmalloc_pool(&c->fill_iter, 1, iter_size)) -- cgit v1.2.3