From be4d234d7aebbfe0c233bc20b9cdef7ab3408ff4 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Mon, 8 Mar 2021 11:37:47 -0700 Subject: bio: add allocation cache abstraction Add a per-cpu bio_set cache for bio allocations, enabling us to quickly recycle them instead of going through the slab allocator. This cache isn't IRQ safe, and hence is only really suitable for polled IO. Very simple - keeps a count of bio's in the cache, and maintains a max of 512 with a slack of 64. If we get above max + slack, we drop slack number of bio's. Reviewed-by: Christoph Hellwig Signed-off-by: Jens Axboe --- block/bio.c | 134 +++++++++++++++++++++++++++++++++++++++++++++++++++++------- 1 file changed, 120 insertions(+), 14 deletions(-) (limited to 'block') diff --git a/block/bio.c b/block/bio.c index 6fa5c653283b..dbb0bc8e1ef7 100644 --- a/block/bio.c +++ b/block/bio.c @@ -25,6 +25,11 @@ #include "blk.h" #include "blk-rq-qos.h" +struct bio_alloc_cache { + struct bio_list free_list; + unsigned int nr; +}; + static struct biovec_slab { int nr_vecs; char *name; @@ -619,6 +624,53 @@ void guard_bio_eod(struct bio *bio) bio_truncate(bio, maxsector << 9); } +#define ALLOC_CACHE_MAX 512 +#define ALLOC_CACHE_SLACK 64 + +static void bio_alloc_cache_prune(struct bio_alloc_cache *cache, + unsigned int nr) +{ + unsigned int i = 0; + struct bio *bio; + + while ((bio = bio_list_pop(&cache->free_list)) != NULL) { + cache->nr--; + bio_free(bio); + if (++i == nr) + break; + } +} + +static int bio_cpu_dead(unsigned int cpu, struct hlist_node *node) +{ + struct bio_set *bs; + + bs = hlist_entry_safe(node, struct bio_set, cpuhp_dead); + if (bs->cache) { + struct bio_alloc_cache *cache = per_cpu_ptr(bs->cache, cpu); + + bio_alloc_cache_prune(cache, -1U); + } + return 0; +} + +static void bio_alloc_cache_destroy(struct bio_set *bs) +{ + int cpu; + + if (!bs->cache) + return; + + cpuhp_state_remove_instance_nocalls(CPUHP_BIO_DEAD, &bs->cpuhp_dead); + for_each_possible_cpu(cpu) { + struct bio_alloc_cache *cache; + + cache = per_cpu_ptr(bs->cache, cpu); + bio_alloc_cache_prune(cache, -1U); + } + free_percpu(bs->cache); +} + /** * bio_put - release a reference to a bio * @bio: bio to release reference to @@ -629,16 +681,23 @@ void guard_bio_eod(struct bio *bio) **/ void bio_put(struct bio *bio) { - if (!bio_flagged(bio, BIO_REFFED)) - bio_free(bio); - else { + if (unlikely(bio_flagged(bio, BIO_REFFED))) { BIO_BUG_ON(!atomic_read(&bio->__bi_cnt)); + if (!atomic_dec_and_test(&bio->__bi_cnt)) + return; + } - /* - * last put frees it - */ - if (atomic_dec_and_test(&bio->__bi_cnt)) - bio_free(bio); + if (bio_flagged(bio, BIO_PERCPU_CACHE)) { + struct bio_alloc_cache *cache; + + bio_uninit(bio); + cache = per_cpu_ptr(bio->bi_pool->cache, get_cpu()); + bio_list_add_head(&cache->free_list, bio); + if (++cache->nr > ALLOC_CACHE_MAX + ALLOC_CACHE_SLACK) + bio_alloc_cache_prune(cache, ALLOC_CACHE_SLACK); + put_cpu(); + } else { + bio_free(bio); } } EXPORT_SYMBOL(bio_put); @@ -1530,6 +1589,7 @@ int biovec_init_pool(mempool_t *pool, int pool_entries) */ void bioset_exit(struct bio_set *bs) { + bio_alloc_cache_destroy(bs); if (bs->rescue_workqueue) destroy_workqueue(bs->rescue_workqueue); bs->rescue_workqueue = NULL; @@ -1591,12 +1651,18 @@ int bioset_init(struct bio_set *bs, biovec_init_pool(&bs->bvec_pool, pool_size)) goto bad; - if (!(flags & BIOSET_NEED_RESCUER)) - return 0; - - bs->rescue_workqueue = alloc_workqueue("bioset", WQ_MEM_RECLAIM, 0); - if (!bs->rescue_workqueue) - goto bad; + if (flags & BIOSET_NEED_RESCUER) { + bs->rescue_workqueue = alloc_workqueue("bioset", + WQ_MEM_RECLAIM, 0); + if (!bs->rescue_workqueue) + goto bad; + } + if (flags & BIOSET_PERCPU_CACHE) { + bs->cache = alloc_percpu(struct bio_alloc_cache); + if (!bs->cache) + goto bad; + cpuhp_state_add_instance_nocalls(CPUHP_BIO_DEAD, &bs->cpuhp_dead); + } return 0; bad: @@ -1623,6 +1689,43 @@ int bioset_init_from_src(struct bio_set *bs, struct bio_set *src) } EXPORT_SYMBOL(bioset_init_from_src); +/** + * bio_alloc_kiocb - Allocate a bio from bio_set based on kiocb + * @kiocb: kiocb describing the IO + * @bs: bio_set to allocate from + * + * Description: + * Like @bio_alloc_bioset, but pass in the kiocb. The kiocb is only + * used to check if we should dip into the per-cpu bio_set allocation + * cache. The allocation uses GFP_KERNEL internally. + * + */ +struct bio *bio_alloc_kiocb(struct kiocb *kiocb, unsigned short nr_vecs, + struct bio_set *bs) +{ + struct bio_alloc_cache *cache; + struct bio *bio; + + if (!(kiocb->ki_flags & IOCB_ALLOC_CACHE) || nr_vecs > BIO_INLINE_VECS) + return bio_alloc_bioset(GFP_KERNEL, nr_vecs, bs); + + cache = per_cpu_ptr(bs->cache, get_cpu()); + bio = bio_list_pop(&cache->free_list); + if (bio) { + cache->nr--; + put_cpu(); + bio_init(bio, nr_vecs ? bio->bi_inline_vecs : NULL, nr_vecs); + bio->bi_pool = bs; + bio_set_flag(bio, BIO_PERCPU_CACHE); + return bio; + } + put_cpu(); + bio = bio_alloc_bioset(GFP_KERNEL, nr_vecs, bs); + bio_set_flag(bio, BIO_PERCPU_CACHE); + return bio; +} +EXPORT_SYMBOL_GPL(bio_alloc_kiocb); + static int __init init_bio(void) { int i; @@ -1637,6 +1740,9 @@ static int __init init_bio(void) SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); } + cpuhp_setup_state_multi(CPUHP_BIO_DEAD, "block/bio:dead", NULL, + bio_cpu_dead); + if (bioset_init(&fs_bio_set, BIO_POOL_SIZE, 0, BIOSET_NEED_BVECS)) panic("bio: can't allocate bios\n"); -- cgit v1.2.3