From: Jens Axboe <axboe@kernel.dk>
Date: Sat, 20 Nov 2021 14:27:57 +0000 (-0700)
Subject: io_uring: clamp CQ size to SQ size
X-Git-Tag: fio-3.29~34
X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=1db268db68823f0fa4c4a4701d3deee88b4c1d84;p=fio.git

io_uring: clamp CQ size to SQ size

By default, io_uring uses twice as big a CQ ring as the SQ ring. That's
to help with cases where completions can come in unexpectedly. This is not
the case for storage IO, so just clamp the CQ size to save a bit of memory
on the CQEs and CQ ring.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---

diff --git a/engines/io_uring.c b/engines/io_uring.c
index 8b8f35f1..00ae3482 100644
--- a/engines/io_uring.c
+++ b/engines/io_uring.c
@@ -692,6 +692,13 @@ static int fio_ioring_queue_init(struct thread_data *td)
 		}
 	}
 
+	/*
+	 * Clamp CQ ring size at our SQ ring size, we don't need more entries
+	 * than that.
+	 */
+	p.flags |= IORING_SETUP_CQSIZE;
+	p.cq_entries = depth;
+
 	ret = syscall(__NR_io_uring_setup, depth, &p);
 	if (ret < 0)
 		return ret;
diff --git a/t/io_uring.c b/t/io_uring.c
index b79822d7..7bf215c7 100644
--- a/t/io_uring.c
+++ b/t/io_uring.c
@@ -384,6 +384,13 @@ static int io_uring_register_files(struct submitter *s)
 
 static int io_uring_setup(unsigned entries, struct io_uring_params *p)
 {
+	/*
+	 * Clamp CQ ring size at our SQ ring size, we don't need more entries
+	 * than that.
+	 */
+	p->flags |= IORING_SETUP_CQSIZE;
+	p->cq_entries = entries;
+
 	return syscall(__NR_io_uring_setup, entries, p);
 }