[RFC PATCH v3 2/4] liburing: add documentation for new napi busy polling

[Stefan Roesch <shr@devkernel.io>]

This adds two man pages for the two new functions:
- io_uring_register_napi_busy_poll_timeout
- io_uring_unregister_napi_busy_poll_timeout

Signed-off-by: Stefan Roesch <shr@devkernel.io>
---
 ...io_uring_register_napi_busy_poll_timeout.3 | 35 +++++++++++++++++++
 man/io_uring_register_napi_prefer_busy_poll.3 | 35 +++++++++++++++++++
 ..._uring_unregister_napi_busy_poll_timeout.3 | 26 ++++++++++++++
 3 files changed, 96 insertions(+)
 create mode 100644 man/io_uring_register_napi_busy_poll_timeout.3
 create mode 100644 man/io_uring_register_napi_prefer_busy_poll.3
 create mode 100644 man/io_uring_unregister_napi_busy_poll_timeout.3

diff --git a/man/io_uring_register_napi_busy_poll_timeout.3 b/man/io_uring_register_napi_busy_poll_timeout.3
new file mode 100644
index 0000000..3acce60
--- /dev/null
+++ b/man/io_uring_register_napi_busy_poll_timeout.3
@@ -0,0 +1,35 @@
+.\" Copyright (C) 2022 Stefan Roesch <shr@devkernel.io>
+.\"
+.\" SPDX-License-Identifier: LGPL-2.0-or-later
+.\"
+.TH io_uring_register_napi_busy_poll_timeout 3 "November 10, 2022" "liburing-2.4" "liburing Manual"
+.SH NAME
+io_uring_register_napi_busy_poll_timeout \- register NAPI busy poll timeout
+.SH SYNOPSIS
+.nf
+.B #include <liburing.h>
+.PP
+.BI "int io_uring_register_napi_busy_poll_timeout(struct io_uring *" ring ","
+.BI "                                             unsigned int " timeout)
+.PP
+.fi
+.SH DESCRIPTION
+.PP
+The
+.BR io_uring_register_napi_busy_poll_timeout (3)
+function registers the NAPI busy poll
+.I timeout
+for subsequent operations.
+
+Registering a NAPI busy poll timeout is a requirement to be able to use
+NAPI busy polling. The other way to enable NAPI busy polling is to set the
+proc setting /proc/sys/net/core/busy_poll.
+
+NAPI busy poll can reduce the network roundtrip time.
+
+
+.SH RETURN VALUE
+On success
+.BR io_uring_register_napi_busy_poll_timeout (3)
+return 0. On failure they return
+.BR -errno .
diff --git a/man/io_uring_register_napi_prefer_busy_poll.3 b/man/io_uring_register_napi_prefer_busy_poll.3
new file mode 100644
index 0000000..713840e
--- /dev/null
+++ b/man/io_uring_register_napi_prefer_busy_poll.3
@@ -0,0 +1,35 @@
+.\" Copyright (C) 2022 Stefan Roesch <shr@devkernel.io>
+.\"
+.\" SPDX-License-Identifier: LGPL-2.0-or-later
+.\"
+.TH io_uring_register_napi_prefer_busy_poll 3 "November 11, 2022" "liburing-2.4" "liburing Manual"
+.SH NAME
+io_uring_register_napi_prefer_busy_poll \- register NAPI prefer busy poll setting
+.SH SYNOPSIS
+.nf
+.B #include <liburing.h>
+.PP
+.BI "int io_uring_register_napi_prefer_busy_poll(struct io_uring *" ring ","
+.BI "                                            bool " prefer_busy_poll)
+.PP
+.fi
+.SH DESCRIPTION
+.PP
+The
+.BR io_uring_register_napi_prefer_busy_poll (3)
+function registers the NAPI
+.I prefer_busy_poll
+for subsequent operations.
+
+Registering a NAPI prefer busy poll seeting sets the mode when calling the
+function napi_busy_loop and corresponds to the SO_PREFER_BUSY_POLL socket
+option.
+
+NAPI prefer busy poll can help in reducng the network roundtrip time.
+
+
+.SH RETURN VALUE
+On success
+.BR io_uring_register_napi_prefer_busy_poll (3)
+return 0. On failure they return
+.BR -errno .
diff --git a/man/io_uring_unregister_napi_busy_poll_timeout.3 b/man/io_uring_unregister_napi_busy_poll_timeout.3
new file mode 100644
index 0000000..666e006
--- /dev/null
+++ b/man/io_uring_unregister_napi_busy_poll_timeout.3
@@ -0,0 +1,26 @@
+.\" Copyright (C) 2022 Stefan Roesch <shr@devkernel.io>
+.\"
+.\" SPDX-License-Identifier: LGPL-2.0-or-later
+.\"
+.TH io_uring_unregister_napi_busy_poll_timeout 3 "November 10, 2022" "liburing-2.4" "liburing Manual"
+.SH NAME
+io_uring_unregister_napi_busy_poll_timeout \- unregister NAPI busy poll timeout
+.SH SYNOPSIS
+.nf
+.B #include <liburing.h>
+.PP
+.BI "int io_uring_unregister_napi_busy_poll_timeout(struct io_uring *" ring ")
+.PP
+.fi
+.SH DESCRIPTION
+.PP
+The
+.BR io_uring_unregister_napi_busy_poll_timeout (3)
+function unregisters the NAPI busy poll
+for subsequent operations.
+
+.SH RETURN VALUE
+On success
+.BR io_uring_unregister_napi_busy_poll_timeout (3)
+return 0. On failure they return
+.BR -errno .
-- 
2.30.2