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authorPavel Begunkov <asml.silence@gmail.com>2022-11-02 15:18:22 +0000
committerJens Axboe <axboe@kernel.dk>2022-11-16 09:44:26 -0700
commitb99182c501c3dedeba4c9e6c92a60df1a2fee119 (patch)
treeb2ef978e4ea4f3e7ea0ea551b5343afb95fc655d
parentf25cf75a452150c243f74ab1f1836822137d5d2c (diff)
bio: add pcpu caching for non-polling bio_put
This patch extends REQ_ALLOC_CACHE to IRQ completions, whenever currently it's only limited to iopoll. Instead of guarding the list with irq toggling on alloc, which is expensive, it keeps an additional irq-safe list from which bios are spliced in batches to ammortise overhead. On the put side it toggles irqs, but in many cases they're already disabled and so cheap. Signed-off-by: Pavel Begunkov <asml.silence@gmail.com> Link: https://lore.kernel.org/r/c2306de96b900ab9264f4428ec37768ddcf0da36.1667384020.git.asml.silence@gmail.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
-rw-r--r--block/bio.c70
1 files changed, 54 insertions, 16 deletions
diff --git a/block/bio.c b/block/bio.c
index 0d03b8d36447..14a7105231d2 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -25,9 +25,15 @@
#include "blk-rq-qos.h"
#include "blk-cgroup.h"
+#define ALLOC_CACHE_THRESHOLD 16
+#define ALLOC_CACHE_SLACK 64
+#define ALLOC_CACHE_MAX 512
+
struct bio_alloc_cache {
struct bio *free_list;
+ struct bio *free_list_irq;
unsigned int nr;
+ unsigned int nr_irq;
};
static struct biovec_slab {
@@ -408,6 +414,22 @@ static void punt_bios_to_rescuer(struct bio_set *bs)
queue_work(bs->rescue_workqueue, &bs->rescue_work);
}
+static void bio_alloc_irq_cache_splice(struct bio_alloc_cache *cache)
+{
+ unsigned long flags;
+
+ /* cache->free_list must be empty */
+ if (WARN_ON_ONCE(cache->free_list))
+ return;
+
+ local_irq_save(flags);
+ cache->free_list = cache->free_list_irq;
+ cache->free_list_irq = NULL;
+ cache->nr += cache->nr_irq;
+ cache->nr_irq = 0;
+ local_irq_restore(flags);
+}
+
static struct bio *bio_alloc_percpu_cache(struct block_device *bdev,
unsigned short nr_vecs, blk_opf_t opf, gfp_t gfp,
struct bio_set *bs)
@@ -417,8 +439,12 @@ static struct bio *bio_alloc_percpu_cache(struct block_device *bdev,
cache = per_cpu_ptr(bs->cache, get_cpu());
if (!cache->free_list) {
- put_cpu();
- return NULL;
+ if (READ_ONCE(cache->nr_irq) >= ALLOC_CACHE_THRESHOLD)
+ bio_alloc_irq_cache_splice(cache);
+ if (!cache->free_list) {
+ put_cpu();
+ return NULL;
+ }
}
bio = cache->free_list;
cache->free_list = bio->bi_next;
@@ -462,9 +488,6 @@ static struct bio *bio_alloc_percpu_cache(struct block_device *bdev,
* submit_bio_noacct() should be avoided - instead, use bio_set's front_pad
* for per bio allocations.
*
- * If REQ_ALLOC_CACHE is set, the final put of the bio MUST be done from process
- * context, not hard/soft IRQ.
- *
* Returns: Pointer to new bio on success, NULL on failure.
*/
struct bio *bio_alloc_bioset(struct block_device *bdev, unsigned short nr_vecs,
@@ -678,11 +701,8 @@ 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)
+static int __bio_alloc_cache_prune(struct bio_alloc_cache *cache,
+ unsigned int nr)
{
unsigned int i = 0;
struct bio *bio;
@@ -694,6 +714,17 @@ static void bio_alloc_cache_prune(struct bio_alloc_cache *cache,
if (++i == nr)
break;
}
+ return i;
+}
+
+static void bio_alloc_cache_prune(struct bio_alloc_cache *cache,
+ unsigned int nr)
+{
+ nr -= __bio_alloc_cache_prune(cache, nr);
+ if (!READ_ONCE(cache->free_list)) {
+ bio_alloc_irq_cache_splice(cache);
+ __bio_alloc_cache_prune(cache, nr);
+ }
}
static int bio_cpu_dead(unsigned int cpu, struct hlist_node *node)
@@ -732,6 +763,12 @@ static inline void bio_put_percpu_cache(struct bio *bio)
struct bio_alloc_cache *cache;
cache = per_cpu_ptr(bio->bi_pool->cache, get_cpu());
+ if (READ_ONCE(cache->nr_irq) + cache->nr > ALLOC_CACHE_MAX) {
+ put_cpu();
+ bio_free(bio);
+ return;
+ }
+
bio_uninit(bio);
if ((bio->bi_opf & REQ_POLLED) && !WARN_ON_ONCE(in_interrupt())) {
@@ -739,13 +776,14 @@ static inline void bio_put_percpu_cache(struct bio *bio)
cache->free_list = bio;
cache->nr++;
} else {
- put_cpu();
- bio_free(bio);
- return;
- }
+ unsigned long flags;
- if (cache->nr > ALLOC_CACHE_MAX + ALLOC_CACHE_SLACK)
- bio_alloc_cache_prune(cache, ALLOC_CACHE_SLACK);
+ local_irq_save(flags);
+ bio->bi_next = cache->free_list_irq;
+ cache->free_list_irq = bio;
+ cache->nr_irq++;
+ local_irq_restore(flags);
+ }
put_cpu();
}