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io_uring: impose max limit on apoll cache

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Caches like this tend to grow to the peak size, and then never get any
smaller. Impose a max limit on the size, to prevent it from growing too
big.

A somewhat randomly chosen 512 is the max size we'll allow the cache
to get. If a batch of frees come in and would bring it over that, we
simply start kfree'ing the surplus.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2022-07-07 14:20:54 -06:00
parent 9b797a37c4
commit 9731bc9855
3 changed files with 17 additions and 3 deletions
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1
include/linux/io_uring_types.h
View file

@ -160,6 +160,7 @@ struct io_ev_fd {
struct io_alloc_cache {
struct hlist_head list;
unsigned int nr_cached;
};
struct io_ring_ctx {

16
io_uring/alloc_cache.h
View file

@ -1,14 +1,24 @@
#ifndef IOU_ALLOC_CACHE_H
#define IOU_ALLOC_CACHE_H
/*
* Don't allow the cache to grow beyond this size.
*/
#define IO_ALLOC_CACHE_MAX 512
struct io_cache_entry {
struct hlist_node node;
};
static inline void io_alloc_cache_put(struct io_alloc_cache *cache,
static inline bool io_alloc_cache_put(struct io_alloc_cache *cache,
struct io_cache_entry *entry)
{
hlist_add_head(&entry->node, &cache->list);
if (cache->nr_cached < IO_ALLOC_CACHE_MAX) {
cache->nr_cached++;
hlist_add_head(&entry->node, &cache->list);
return true;
}
return false;
}
static inline struct io_cache_entry *io_alloc_cache_get(struct io_alloc_cache *cache)
@ -26,6 +36,7 @@ static inline struct io_cache_entry *io_alloc_cache_get(struct io_alloc_cache *c
static inline void io_alloc_cache_init(struct io_alloc_cache *cache)
{
INIT_HLIST_HEAD(&cache->list);
cache->nr_cached = 0;
}
static inline void io_alloc_cache_free(struct io_alloc_cache *cache,
@ -37,5 +48,6 @@ static inline void io_alloc_cache_free(struct io_alloc_cache *cache,
hlist_del(node);
free(container_of(node, struct io_cache_entry, node));
}
cache->nr_cached = 0;
}
#endif

3
io_uring/io_uring.c
View file

@ -1181,7 +1181,8 @@ void io_free_batch_list(struct io_ring_ctx *ctx, struct io_wq_work_node *node)
if (apoll->double_poll)
kfree(apoll->double_poll);
io_alloc_cache_put(&ctx->apoll_cache, &apoll->cache);
if (!io_alloc_cache_put(&ctx->apoll_cache, &apoll->cache))
kfree(apoll);
req->flags &= ~REQ_F_POLLED;
}
if (req->flags & IO_REQ_LINK_FLAGS)