linux-kernel - [PATCH v2 8/8] io_uring: optimise req bulk allocation cache

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Date:   Sat, 25 Jan 2020 22:53:45 +0300
From:   Pavel Begunkov <asml.silence@...il.com>
To:     Jens Axboe <axboe@...nel.dk>, io-uring@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 8/8] io_uring: optimise req bulk allocation cache

Traverse backward through @reqs in struct io_submit_state, so it's
possible to remove cur_req from it and easier to handle in general.

Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
---
 fs/io_uring.c | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 82df6171baae..744e8a90b543 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -206,7 +206,6 @@ struct io_submit_state {
 	 */
 	void			*reqs[IO_IOPOLL_BATCH];
 	unsigned int		free_reqs;
-	unsigned int		cur_req;
 
 	/*
 	 * File reference cache
@@ -839,9 +838,7 @@ static void io_init_submit_state(struct io_ring_ctx *ctx)
 	struct io_submit_state *state = &ctx->submit_state;
 
 	state->mm = (ctx->flags & IORING_SETUP_SQPOLL) ? NULL : ctx->sqo_mm;
-
 	state->free_reqs = 0;
-	state->cur_req = 0;
 }
 
 static void io_clear_submit_state(struct io_ring_ctx *ctx)
@@ -849,8 +846,7 @@ static void io_clear_submit_state(struct io_ring_ctx *ctx)
 	struct io_submit_state *state = &ctx->submit_state;
 
 	if (state->free_reqs)
-		kmem_cache_free_bulk(req_cachep, state->free_reqs,
-					&state->reqs[state->cur_req]);
+		kmem_cache_free_bulk(req_cachep, state->free_reqs, state->reqs);
 }
 
 static inline bool __req_need_defer(struct io_kiocb *req)
@@ -1167,12 +1163,10 @@ static struct io_kiocb *io_get_req(struct io_ring_ctx *ctx)
 			ret = 1;
 		}
 		state->free_reqs = ret - 1;
-		state->cur_req = 1;
-		req = state->reqs[0];
+		req = state->reqs[ret - 1];
 	} else {
-		req = state->reqs[state->cur_req];
 		state->free_reqs--;
-		state->cur_req++;
+		req = state->reqs[state->free_reqs];
 	}
 
 got_it:
-- 
2.24.0