[PATCH 5.13 245/351] io_uring: dont bounce submit_state cachelines

Greg Kroah-Hartman
2021-07-19T17:51:08Z

From: Pavel Begunkov <asml.silence@gmail.com>

[ Upstream commit d0acdee296d42e700c16271d9f95085a9c897a53 ]

struct io_submit_state contains struct io_comp_state and so
locked_free_*, that renders cachelines around ->locked_free* being
invalidated on most non-inline completions, that may terrorise caches if
submissions and completions are done by different tasks.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/290cb5412b76892e8631978ee8ab9db0c6290dd5.1621201931.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/io_uring.c | 20 +++++++++-----------
1 file changed, 9 insertions(+), 11 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 5d685c92b8fd..bf3566ff9516 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -299,11 +299,8 @@ struct io_sq_data {
struct io_comp_state {
struct io_kiocb *reqs[IO_COMPL_BATCH];
unsigned int nr;
- unsigned int locked_free_nr;
/* inline/task_work completion list, under ->uring_lock */
struct list_head free_list;
- /* IRQ completion list, under ->completion_lock */
- struct list_head locked_free_list;
};

struct io_submit_link {
@@ -382,6 +379,9 @@ struct io_ring_ctx {
} ____cacheline_aligned_in_smp;

struct io_submit_state submit_state;
+ /* IRQ completion list, under ->completion_lock */
+ struct list_head locked_free_list;
+ unsigned int locked_free_nr;

struct io_rings *rings;

@@ -1193,7 +1193,7 @@ static struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
init_llist_head(&ctx->rsrc_put_llist);
INIT_LIST_HEAD(&ctx->tctx_list);
INIT_LIST_HEAD(&ctx->submit_state.comp.free_list);
- INIT_LIST_HEAD(&ctx->submit_state.comp.locked_free_list);
+ INIT_LIST_HEAD(&ctx->locked_free_list);
return ctx;
err:
kfree(ctx->dummy_ubuf);
@@ -1590,8 +1590,6 @@ static void io_req_complete_post(struct io_kiocb *req, long res,
* free_list cache.
*/
if (req_ref_put_and_test(req)) {
- struct io_comp_state *cs = &ctx->submit_state.comp;
-
if (req->flags & (REQ_F_LINK | REQ_F_HARDLINK)) {
if (req->flags & (REQ_F_LINK_TIMEOUT | REQ_F_FAIL_LINK))
io_disarm_next(req);
@@ -1602,8 +1600,8 @@ static void io_req_complete_post(struct io_kiocb *req, long res,
}
io_dismantle_req(req);
io_put_task(req->task, 1);
- list_add(&req->compl.list, &cs->locked_free_list);
- cs->locked_free_nr++;
+ list_add(&req->compl.list, &ctx->locked_free_list);
+ ctx->locked_free_nr++;
} else {
if (!percpu_ref_tryget(&ctx->refs))
req = NULL;
@@ -1658,8 +1656,8 @@ static void io_flush_cached_locked_reqs(struct io_ring_ctx *ctx,
struct io_comp_state *cs)
{
spin_lock_irq(&ctx->completion_lock);
- list_splice_init(&cs->locked_free_list, &cs->free_list);
- cs->locked_free_nr = 0;
+ list_splice_init(&ctx->locked_free_list, &cs->free_list);
+ ctx->locked_free_nr = 0;
spin_unlock_irq(&ctx->completion_lock);
}

@@ -1675,7 +1673,7 @@ static bool io_flush_cached_reqs(struct io_ring_ctx *ctx)
* locked cache, grab the lock and move them over to our submission
* side cache.
*/
- if (READ_ONCE(cs->locked_free_nr) > IO_COMPL_BATCH)
+ if (READ_ONCE(ctx->locked_free_nr) > IO_COMPL_BATCH)
io_flush_cached_locked_reqs(ctx, cs);

nr = state->free_reqs;
--
2.30.2