Now that do have a nicer interface to work against we can add Linux native
AIO support. It's an extremly thing layer just setting up an iocb for
the io_submit system call in the submission path, and registering an
eventfd with the qemu poll handler to do complete the iocbs directly
from there.
This started out based on Anthony's earlier AIO patch, but after
estimated 42,000 rewrites and just as many build system changes
there's not much left of it.
To enable native kernel aio use the aio=native sub-command on the
drive command line. I have also added an option to qemu-io to
test the aio support without needing a guest.
Signed-off-by: Christoph Hellwig<address@hidden>
Index: qemu/Makefile
===================================================================
--- qemu.orig/Makefile 2009-08-19 22:49:08.789354196 -0300
+++ qemu/Makefile 2009-08-19 22:51:25.293352541 -0300
@@ -56,6 +56,7 @@ recurse-all: $(SUBDIR_RULES) $(ROMSUBDIR
block-obj-y = cutils.o cache-utils.o qemu-malloc.o qemu-option.o module.o
block-obj-y += nbd.o block.o aio.o aes.o
block-obj-$(CONFIG_POSIX) += posix-aio-compat.o
+block-obj-$(CONFIG_LINUX_AIO) += linux-aio.o
block-nested-y += cow.o qcow.o vdi.o vmdk.o cloop.o dmg.o bochs.o vpc.o
vvfat.o
block-nested-y += qcow2.o qcow2-refcount.o qcow2-cluster.o qcow2-snapshot.o
Index: qemu/block/raw-posix.c
===================================================================
--- qemu.orig/block/raw-posix.c 2009-08-19 22:49:08.793352540 -0300
+++ qemu/block/raw-posix.c 2009-08-19 23:00:21.157402768 -0300
@@ -115,6 +115,7 @@ typedef struct BDRVRawState {
int fd_got_error;
int fd_media_changed;
#endif
+ int use_aio;
uint8_t* aligned_buf;
} BDRVRawState;
@@ -159,6 +160,7 @@ static int raw_open_common(BlockDriverSt
}
s->fd = fd;
s->aligned_buf = NULL;
+
if ((bdrv_flags& BDRV_O_NOCACHE)) {
s->aligned_buf = qemu_blockalign(bs, ALIGNED_BUFFER_SIZE);
if (s->aligned_buf == NULL) {
@@ -166,9 +168,22 @@ static int raw_open_common(BlockDriverSt
}
}
- s->aio_ctx = paio_init();
- if (!s->aio_ctx) {
- goto out_free_buf;
+#ifdef CONFIG_LINUX_AIO
+ if ((bdrv_flags& (BDRV_O_NOCACHE|BDRV_O_NATIVE_AIO)) ==
+ (BDRV_O_NOCACHE|BDRV_O_NATIVE_AIO)) {
+ s->aio_ctx = laio_init();
+ if (!s->aio_ctx) {
+ goto out_free_buf;
+ }
+ s->use_aio = 1;
+ } else
+#endif
+ {
+ s->aio_ctx = paio_init();
+ if (!s->aio_ctx) {
+ goto out_free_buf;
+ }
+ s->use_aio = 0;
}
return 0;
@@ -524,8 +539,13 @@ static BlockDriverAIOCB *raw_aio_submit(
* boundary. Check if this is the case or telll the low-level
* driver that it needs to copy the buffer.
*/
- if (s->aligned_buf&& !qiov_is_aligned(qiov)) {
- type |= QEMU_AIO_MISALIGNED;
+ if (s->aligned_buf) {
+ if (!qiov_is_aligned(qiov)) {
+ type |= QEMU_AIO_MISALIGNED;
+ } else if (s->use_aio) {
+ return laio_submit(bs, s->aio_ctx, s->fd, sector_num, qiov,
+ nb_sectors, cb, opaque, type);
+ }
}
return paio_submit(bs, s->aio_ctx, s->fd, sector_num, qiov, nb_sectors,
Index: qemu/configure
===================================================================
--- qemu.orig/configure 2009-08-19 22:49:08.801352719 -0300
+++ qemu/configure 2009-08-19 22:51:25.305393736 -0300
@@ -197,6 +197,7 @@ build_docs="yes"
uname_release=""
curses="yes"
curl="yes"
+linux_aio="yes"
io_thread="no"
nptl="yes"
mixemu="no"
@@ -499,6 +500,8 @@ for opt do
;;
--enable-mixemu) mixemu="yes"
;;
+ --disable-linux-aio) linux_aio="no"
+ ;;
--enable-io-thread) io_thread="yes"
;;
--disable-blobs) blobs="no"
@@ -636,6 +639,7 @@ echo " --oss-lib path to
echo " --enable-uname-release=R Return R for uname -r in usermode emulation"
echo " --sparc_cpu=V Build qemu for Sparc architecture v7, v8, v8plus,
v8plusa, v9"
echo " --disable-vde disable support for vde network"
+echo " --disable-linux-aio disable Linux AIO support"
echo " --enable-io-thread enable IO thread"
echo " --disable-blobs disable installing provided firmware blobs"
echo " --kerneldir=PATH look for kernel includes in PATH"
@@ -1197,6 +1201,23 @@ if test "$pthread" = no; then
fi
##########################################
+# linux-aio probe
+AIOLIBS=""
+
+if test "$linux_aio" = "yes" ; then
+ linux_aio=no
+ cat> $TMPC<<EOF
+#include<libaio.h>
+#include<sys/eventfd.h>
+int main(void) { io_setup(0, NULL); io_set_eventfd(NULL, 0); eventfd(0, 0);
return 0; }
+EOF
+ if compile_prog "" "-laio" ; then
+ linux_aio=yes
+ LIBS="$LIBS -laio"
+ fi
+fi
+
+##########################################
# iovec probe
cat> $TMPC<<EOF
#include<sys/types.h>
@@ -1527,6 +1548,7 @@ echo "NPTL support $nptl"
echo "GUEST_BASE $guest_base"
echo "vde support $vde"
echo "IO thread $io_thread"
+echo "Linux AIO support $linux_aio"
echo "Install blobs $blobs"
echo -e "KVM support $kvm"
echo "fdt support $fdt"
@@ -1700,6 +1722,9 @@ fi
if test "$io_thread" = "yes" ; then
echo "CONFIG_IOTHREAD=y">> $config_host_mak
fi
+if test "$linux_aio" = "yes" ; then
+ echo "CONFIG_LINUX_AIO=y">> $config_host_mak
+fi
if test "$blobs" = "yes" ; then
echo "INSTALL_BLOBS=yes">> $config_host_mak
fi
Index: qemu/linux-aio.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ qemu/linux-aio.c 2009-08-20 10:54:10.924375300 -0300
@@ -0,0 +1,204 @@
+/*
+ * Linux native AIO support.
+ *
+ * Copyright (C) 2009 IBM, Corp.
+ * Copyright (C) 2009 Red Hat, Inc.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+#include "qemu-common.h"
+#include "qemu-aio.h"
+#include "block_int.h"
+#include "block/raw-posix-aio.h"
+
+#include<sys/eventfd.h>
+#include<libaio.h>
+
+/*
+ * Queue size (per-device).
+ *
+ * XXX: eventually we need to communicate this to the guest and/or make it
+ * tunable by the guest. If we get more outstanding requests at a time
+ * than this we will get EAGAIN from io_submit which is communicated to
+ * the guest as an I/O error.
+ */
+#define MAX_EVENTS 128