linux-kernel - [PATCH v2 2/2] io_uring: Create define to modify a SQPOLL parameter

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Date:   Wed, 23 Jun 2021 11:50:18 -0700
From:   Olivier Langlois <olivier@...llion01.com>
To:     Jens Axboe <axboe@...nel.dk>,
        Pavel Begunkov <asml.silence@...il.com>,
        io-uring@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Olivier Langlois <olivier@...llion01.com>
Subject: [PATCH v2 2/2] io_uring: Create define to modify a SQPOLL parameter

The magic number used to cap the number of entries extracted from an
io_uring instance SQ before moving to the other instances is an
interesting parameter to experiment with.

A define has been created to make it easy to change its value from a
single location.

Signed-off-by: Olivier Langlois <olivier@...llion01.com>
---
 fs/io_uring.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 7c545fa66f31..e7997f9bf879 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -89,6 +89,7 @@
 
 #define IORING_MAX_ENTRIES	32768
 #define IORING_MAX_CQ_ENTRIES	(2 * IORING_MAX_ENTRIES)
+#define IORING_SQPOLL_CAP_ENTRIES_VALUE 8
 
 /*
  * Shift of 9 is 512 entries, or exactly one page on 64-bit archs
@@ -6797,8 +6798,8 @@ static int __io_sq_thread(struct io_ring_ctx *ctx, bool cap_entries)
 
 	to_submit = io_sqring_entries(ctx);
 	/* if we're handling multiple rings, cap submit size for fairness */
-	if (cap_entries && to_submit > 8)
-		to_submit = 8;
+	if (cap_entries && to_submit > IORING_SQPOLL_CAP_ENTRIES_VALUE)
+		to_submit = IORING_SQPOLL_CAP_ENTRIES_VALUE;
 
 	if (!list_empty(&ctx->iopoll_list) || to_submit) {
 		unsigned nr_events = 0;
-- 
2.32.0