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block: use singly linked list for bio cache 

Pointless to maintain a head/tail for the list, as we never need to
access the tail. Entries are always LIFO for cache hotness reasons.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2021-12-01 16:19:18 -07:00
parent 5581a5ddfe
commit fcade2ce06
1 changed files with 8 additions and 5 deletions
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13
block/bio.c
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@ -26,7 +26,7 @@
#include "blk-rq-qos.h"
struct bio_alloc_cache {
struct bio_list free_list;
struct bio *free_list;
unsigned int nr;
};
@ -630,7 +630,8 @@ static void bio_alloc_cache_prune(struct bio_alloc_cache *cache,
unsigned int i = 0;
struct bio *bio;
while ((bio = bio_list_pop(&cache->free_list)) != NULL) {
while ((bio = cache->free_list) != NULL) {
cache->free_list = bio->bi_next;
cache->nr--;
bio_free(bio);
if (++i == nr)
@ -689,7 +690,8 @@ void bio_put(struct bio *bio)
bio_uninit(bio);
cache = per_cpu_ptr(bio->bi_pool->cache, get_cpu());
bio_list_add_head(&cache->free_list, bio);
bio->bi_next = cache->free_list;
cache->free_list = bio;
if (++cache->nr > ALLOC_CACHE_MAX + ALLOC_CACHE_SLACK)
bio_alloc_cache_prune(cache, ALLOC_CACHE_SLACK);
put_cpu();
@ -1704,8 +1706,9 @@ struct bio *bio_alloc_kiocb(struct kiocb *kiocb, unsigned short nr_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) {
if (cache->free_list) {
bio = cache->free_list;
cache->free_list = bio->bi_next;
cache->nr--;
put_cpu();
bio_init(bio, nr_vecs ? bio->bi_inline_vecs : NULL, nr_vecs);