[liburing,1/1] man/io_uring_setup.2: document IORING_SETUP_SINGLE_ISSUER

Commit Message

Pavel Begunkov July 22, 2022, 11:49 a.m. UTC

Signed-off-by: Pavel Begunkov <[e-mail]>
---
 man/io_uring_setup.2 | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

Comments

Jens Axboe July 22, 2022, 3:21 p.m. UTC | #1

On Fri, 22 Jul 2022 12:49:02 +0100, Pavel Begunkov wrote:
> 


Applied, thanks!

[1/1] man/io_uring_setup.2: document IORING_SETUP_SINGLE_ISSUER
      commit: 02adcf497c9f4ca20175b291f8269faff4da958c

Best regards,

Patch

diff --git a/man/io_uring_setup.2 b/man/io_uring_setup.2
index 75c69ff..0f57d8f 100644
--- a/man/io_uring_setup.2
+++ b/man/io_uring_setup.2
@@ -239,6 +239,24 @@  variant. This is a requirement for using certain request types, as of 5.19
 only the
 .B IORING_OP_URING_CMD
 passthrough command for NVMe passthrough needs this. Available since 5.19.
+.TP
+.B IORING_SETUP_SINGLE_ISSUER
+A hint to the kernel that only a single task can submit requests, which is used
+for internal optimisations. The kernel enforces the rule, which only affects
+.I
+io_uring_enter(2)
+calls submitting requests and will fail them with
+.B -EEXIST
+if the restriction is violated.
+The submitter task may differ from the task that created the ring.
+Note that when
+.B IORING_SETUP_SQPOLL
+is set it is considered that the polling task is doing all submissions
+on behalf of the userspace and so it always complies with the rule disregarding
+how many userspace tasks do
+.I
+io_uring_enter(2).
+Available since 5.20.
 .PP
 If no flags are specified, the io_uring instance is setup for
 interrupt driven I/O.  I/O may be submitted using