io_uring: optimise kiocb layout
We want ->comp_list in the second cacheline, which is hotter comparing
to the 3rd. Swap the field with ->link, which is not as hot and
controlled by flags and so not accessed unless there is a link.
By the way add a couple of comments for io_kiocb fields.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/9d9dde31f8f62279a5f48c575bbc27b8290edc0c.1633373302.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 5b3b4f8..ab07a08 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -863,19 +863,22 @@ struct io_kiocb {
struct task_struct *task;
u64 user_data;
- struct io_kiocb *link;
struct percpu_ref *fixed_rsrc_refs;
- /* used with ctx->iopoll_list with reads/writes */
+ /* used by request caches, completion batching and iopoll */
struct io_wq_work_node comp_list;
+ struct io_kiocb *link;
struct io_task_work io_task_work;
/* for polled requests, i.e. IORING_OP_POLL_ADD and async armed poll */
struct hlist_node hash_node;
+ /* internal polling, see IORING_FEAT_FAST_POLL */
struct async_poll *apoll;
/* store used ubuf, so we can prevent reloading */
struct io_mapped_ubuf *imu;
struct io_wq_work work;
+ /* custom credentials, valid IFF REQ_F_CREDS is set */
const struct cred *creds;
+ /* stores selected buf, valid IFF REQ_F_BUFFER_SELECTED is set */
struct io_buffer *kbuf;
};
