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>
This commit is contained in:
Pavel Begunkov 2021-10-04 20:02:46 +01:00 committed by Jens Axboe
parent 6224590d24
commit 7e3709d576

View File

@ -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;
};