io_uring/alloc_cache: switch to array based caching

Currently lists are being used to manage this, but best practice is
usually to have these in an array instead as that it cheaper to manage.

Outside of that detail, games are also played with KASAN as the list
is inside the cached entry itself.

Finally, all users of this need a struct io_cache_entry embedded in
their struct, which is union'ized with something else in there that
isn't used across the free -> realloc cycle.

Get rid of all of that, and simply have it be an array. This will not
change the memory used, as we're just trading an 8-byte member entry
for the per-elem array size.

This reduces the overhead of the recycled allocations, and it reduces
the amount of code code needed to support recycling to about half of
what it currently is.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 1 insertions, 1 deletions

diff --git a/include/linux/io_uring_types.h b/include/linux/io_uring_types.h
index 0f24fdad19c2..ef45b8bd1b35 100644
--- a/include/linux/io_uring_types.h
+++ b/include/linux/io_uring_types.h
@@ -220,7 +220,7 @@ struct io_ev_fd {
 };
 
 struct io_alloc_cache {
-	struct io_wq_work_node	list;
+	void			**entries;
 	unsigned int		nr_cached;
 	unsigned int		max_cached;
 	size_t			elem_size;