[Qemu-devel] [PATCH v6 00/14] Add support for io_uring

[Qemu-devel] [PATCH v6 00/14] Add support for io_uring

[Aarushi Mehta]

This patch series adds support for the newly developed io_uring Linux AIO
interface. Linux io_uring is faster than Linux's AIO asynchronous I/O code,
offers efficient buffered asynchronous I/O support, the ability to do I/O
without performing a system call via polled I/O, and other efficiency enhancements.

Testing it requires a host kernel (5.1+) and the liburing library.
Use the option -drive aio=io_uring to enable it.

Benchmarks for the system at https://github.com/rooshm/benchmarks
io_uring has similar performance as libaio but supports cache=writeback.
Further performance enhancement will be implemented

There is currently an -EIO output when guests are booted from io_uring
disks for the second time with clean shutdowns that is being investigated.

v6:
- add slow path for short-read
- hooks up fsync
- enables qemu-iotests with aio options
- adds bdrv_parse_aio

v5:
- Adds completion polling
- Extends qemu-io
- Adds qemu-iotest

v4:
- Add error handling
- Add trace events
- Remove aio submission based code

Aarushi Mehta (14):
  configure: permit use of io_uring
  qapi/block-core: add option for io_uring
  block/block: add BDRV flag for io_uring
  block/io_uring: implements interfaces for io_uring
  stubs: add stubs for io_uring interface
  util/async: add aio interfaces for io_uring
  blockdev: accept io_uring as option
  block/file-posix.c: extend to use io_uring
  block: add trace events for io_uring
  block/io_uring: adds userspace completion polling
  qemu-io: adds option to use aio engine
  qemu-img: adds option to use aio engine
  qemu-nbd: adds option for aio engines
  tests/qemu-iotest: enable testing with qemu-io aio options

 MAINTAINERS                  |   8 +
 block.c                      |  22 ++
 block/Makefile.objs          |   3 +
 block/file-posix.c           |  99 ++++++--
 block/io_uring.c             | 439 +++++++++++++++++++++++++++++++++++
 block/trace-events           |  12 +
 blockdev.c                   |  12 +-
 configure                    |  27 +++
 include/block/aio.h          |  16 +-
 include/block/block.h        |   2 +
 include/block/raw-aio.h      |  12 +
 qapi/block-core.json         |   4 +-
 qemu-img.c                   |  11 +-
 qemu-io.c                    |  25 +-
 qemu-nbd.c                   |  12 +-
 stubs/Makefile.objs          |   1 +
 stubs/io_uring.c             |  32 +++
 tests/qemu-iotests/check     |  14 +-
 tests/qemu-iotests/common.rc |  10 +
 util/async.c                 |  36 +++
 20 files changed, 746 insertions(+), 51 deletions(-)
 create mode 100644 block/io_uring.c
 create mode 100644 stubs/io_uring.c

-- 
2.21.0

[Qemu-devel] [PATCH v6 01/14] configure: permit use of io_uring

[Aarushi Mehta]

Signed-off-by: Aarushi Mehta <mehta.aaru20@gmail.com>
---
 configure | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/configure b/configure
index eb635c3b9a..b0e2e2158e 100755
--- a/configure
+++ b/configure
@@ -370,6 +370,7 @@ xen=""
 xen_ctrl_version=""
 xen_pci_passthrough=""
 linux_aio=""
+linux_io_uring=""
 cap_ng=""
 attr=""
 libattr=""
@@ -1271,6 +1272,10 @@ for opt do
   ;;
   --enable-linux-aio) linux_aio="yes"
   ;;
+  --disable-linux-io-uring) linux_io_uring="no"
+  ;;
+  --enable-linux-io-uring) linux_io_uring="yes"
+  ;;
   --disable-attr) attr="no"
   ;;
   --enable-attr) attr="yes"
@@ -1789,6 +1794,7 @@ disabled with --disable-FEATURE, default is enabled if available:
   vde             support for vde network
   netmap          support for netmap network
   linux-aio       Linux AIO support
+  linux-io-uring  Linux io_uring support
   cap-ng          libcap-ng support
   attr            attr and xattr support
   vhost-net       vhost-net kernel acceleration support
@@ -3969,6 +3975,21 @@ EOF
     linux_aio=no
   fi
 fi
+##########################################
+# linux-io-uring probe
+
+if test "$linux_io_uring" != "no" ; then
+  if $pkg_config liburing; then
+    linux_io_uring_cflags=$($pkg_config --cflags liburing)
+    linux_io_uring_libs=$($pkg_config --libs liburing)
+    linux_io_uring=yes
+  else
+    if test "$linux_io_uring" = "yes" ; then
+      feature_not_found "linux io_uring" "Install liburing devel"
+    fi
+    linux_io_uring=no
+  fi
+fi
 
 ##########################################
 # TPM emulation is only on POSIX
@@ -6392,6 +6413,7 @@ echo "PIE               $pie"
 echo "vde support       $vde"
 echo "netmap support    $netmap"
 echo "Linux AIO support $linux_aio"
+echo "Linux io_uring support $linux_io_uring"
 echo "ATTR/XATTR support $attr"
 echo "Install blobs     $blobs"
 echo "KVM support       $kvm"
@@ -6878,6 +6900,11 @@ fi
 if test "$linux_aio" = "yes" ; then
   echo "CONFIG_LINUX_AIO=y" >> $config_host_mak
 fi
+if test "$linux_io_uring" = "yes" ; then
+  echo "CONFIG_LINUX_IO_URING=y" >> $config_host_mak
+  echo "LINUX_IO_URING_CFLAGS=$linux_io_uring_cflags" >> $config_host_mak
+  echo "LINUX_IO_URING_LIBS=$linux_io_uring_libs" >> $config_host_mak
+fi
 if test "$attr" = "yes" ; then
   echo "CONFIG_ATTR=y" >> $config_host_mak
 fi
-- 
2.21.0

[Qemu-devel] [PATCH v6 02/14] qapi/block-core: add option for io_uring

[Aarushi Mehta]

Only enumerates option for devices that support it

Signed-off-by: Aarushi Mehta <mehta.aaru20@gmail.com>
---
 qapi/block-core.json | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/qapi/block-core.json b/qapi/block-core.json
index 0d43d4f37c..0a3d4ae7d2 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -2792,11 +2792,13 @@
 #
 # @threads:     Use qemu's thread pool
 # @native:      Use native AIO backend (only Linux and Windows)
+# @io_uring:    Use linux io_uring (since 4.1)
 #
 # Since: 2.9
 ##
 { 'enum': 'BlockdevAioOptions',
-  'data': [ 'threads', 'native' ] }
+  'data': [ 'threads', 'native',
+            { 'name': 'io_uring', 'if': 'defined(CONFIG_LINUX_IO_URING)' } ] }
 
 ##
 # @BlockdevCacheOptions:
-- 
2.21.0

[Qemu-devel] [PATCH v6 01/14] configure: permit use of io_uring

[Aarushi Mehta]

Signed-off-by: Aarushi Mehta <mehta.aaru20@gmail.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Maxim Levitsky <maximlevitsky@gmail.com>
---
 configure | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/configure b/configure
index eb635c3b9a..b0e2e2158e 100755
--- a/configure
+++ b/configure
@@ -370,6 +370,7 @@ xen=""
 xen_ctrl_version=""
 xen_pci_passthrough=""
 linux_aio=""
+linux_io_uring=""
 cap_ng=""
 attr=""
 libattr=""
@@ -1271,6 +1272,10 @@ for opt do
   ;;
   --enable-linux-aio) linux_aio="yes"
   ;;
+  --disable-linux-io-uring) linux_io_uring="no"
+  ;;
+  --enable-linux-io-uring) linux_io_uring="yes"
+  ;;
   --disable-attr) attr="no"
   ;;
   --enable-attr) attr="yes"
@@ -1789,6 +1794,7 @@ disabled with --disable-FEATURE, default is enabled if available:
   vde             support for vde network
   netmap          support for netmap network
   linux-aio       Linux AIO support
+  linux-io-uring  Linux io_uring support
   cap-ng          libcap-ng support
   attr            attr and xattr support
   vhost-net       vhost-net kernel acceleration support
@@ -3969,6 +3975,21 @@ EOF
     linux_aio=no
   fi
 fi
+##########################################
+# linux-io-uring probe
+
+if test "$linux_io_uring" != "no" ; then
+  if $pkg_config liburing; then
+    linux_io_uring_cflags=$($pkg_config --cflags liburing)
+    linux_io_uring_libs=$($pkg_config --libs liburing)
+    linux_io_uring=yes
+  else
+    if test "$linux_io_uring" = "yes" ; then
+      feature_not_found "linux io_uring" "Install liburing devel"
+    fi
+    linux_io_uring=no
+  fi
+fi
 
 ##########################################
 # TPM emulation is only on POSIX
@@ -6392,6 +6413,7 @@ echo "PIE               $pie"
 echo "vde support       $vde"
 echo "netmap support    $netmap"
 echo "Linux AIO support $linux_aio"
+echo "Linux io_uring support $linux_io_uring"
 echo "ATTR/XATTR support $attr"
 echo "Install blobs     $blobs"
 echo "KVM support       $kvm"
@@ -6878,6 +6900,11 @@ fi
 if test "$linux_aio" = "yes" ; then
   echo "CONFIG_LINUX_AIO=y" >> $config_host_mak
 fi
+if test "$linux_io_uring" = "yes" ; then
+  echo "CONFIG_LINUX_IO_URING=y" >> $config_host_mak
+  echo "LINUX_IO_URING_CFLAGS=$linux_io_uring_cflags" >> $config_host_mak
+  echo "LINUX_IO_URING_LIBS=$linux_io_uring_libs" >> $config_host_mak
+fi
 if test "$attr" = "yes" ; then
   echo "CONFIG_ATTR=y" >> $config_host_mak
 fi
-- 
2.21.0