Re: [Qemu-devel] [PATCH v2 1/2] raw-posix: warn about BDRV_O_NATIVE_AIO if libaio is unavailable
Am 23.07.2015 um 12:09 hat Christian Borntraeger geschrieben: Am 17.07.2015 um 16:23 schrieb Stefan Hajnoczi: raw-posix.c silently ignores BDRV_O_NATIVE_AIO if libaio is unavailable. It is confusing when aio=native performance is identical to aio=threads because the binary was accidentally built without libaio. Print a deprecation warning if -drive aio=native is used with a binary that does not support libaio. There are probably users using aio=native who would be inconvenienced if QEMU suddenly refused to start their guests. In the future this will become an error. Signed-off-by: Stefan Hajnoczi stefa...@redhat.com had that myself on a freshly installed system without libaio-devel. Acked-by: Christian Borntraeger borntrae...@de.ibm.com Another thing. Would it make sense to change the default to aio=native somewhen? From what I can tell this seems to outperform aio=threads in most cases. aio=native requires cache.direct=on, which is not portable to all platforms that qemu supports, and also doesn't work with all filesystems on Linux (most notably tmpfs fails). Also recent benchmarks seem to suggest that currently there is no clear winner between aio=native and aio=threads, it depends too much on the host storage and the workload. When we discussed the default cache mode a while back (with the options cache=writeback and cache=none), it was considered more important to have a default setting that works everywhere and performs good for quick ad-hoc VMs and development/debugging work than one that performs best in enterprise setups that should use a management tool anyway. Kevin
Re: [Qemu-devel] [PATCH v2 1/2] raw-posix: warn about BDRV_O_NATIVE_AIO if libaio is unavailable
Am 17.07.2015 um 16:23 schrieb Stefan Hajnoczi:
raw-posix.c silently ignores BDRV_O_NATIVE_AIO if libaio is unavailable.
It is confusing when aio=native performance is identical to aio=threads
because the binary was accidentally built without libaio.
Print a deprecation warning if -drive aio=native is used with a binary
that does not support libaio. There are probably users using aio=native
who would be inconvenienced if QEMU suddenly refused to start their
guests. In the future this will become an error.
Signed-off-by: Stefan Hajnoczi stefa...@redhat.com
had that myself on a freshly installed system without libaio-devel.
Acked-by: Christian Borntraeger borntrae...@de.ibm.com
Another thing. Would it make sense to change the default to aio=native somewhen?
From what I can tell this seems to outperform aio=threads in most cases.
---
block/raw-posix.c | 11 ++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/block/raw-posix.c b/block/raw-posix.c
index 855febe..e09019c 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -519,7 +519,16 @@ static int raw_open_common(BlockDriverState *bs, QDict
*options,
future QEMU versions.\n,
bs-filename);
}
-#endif
+#else
+if (bdrv_flags BDRV_O_NATIVE_AIO) {
+error_printf(WARNING: aio=native was specified for '%s', but
+ is not supported in this build. Falling back to
+ aio=threads.\n
+ This will become an error condition in
+ future QEMU versions.\n,
+ bs-filename);
+}
+#endif /* !defined(CONFIG_LINUX_AIO) */
s-has_discard = true;
s-has_write_zeroes = true;
Re: [Qemu-devel] [PATCH v2 1/2] raw-posix: warn about BDRV_O_NATIVE_AIO if libaio is unavailable
On 07/23/2015 01:09 PM, Christian Borntraeger wrote:
Am 17.07.2015 um 16:23 schrieb Stefan Hajnoczi:
raw-posix.c silently ignores BDRV_O_NATIVE_AIO if libaio is unavailable.
It is confusing when aio=native performance is identical to aio=threads
because the binary was accidentally built without libaio.
Print a deprecation warning if -drive aio=native is used with a binary
that does not support libaio. There are probably users using aio=native
who would be inconvenienced if QEMU suddenly refused to start their
guests. In the future this will become an error.
Signed-off-by: Stefan Hajnoczi stefa...@redhat.com
had that myself on a freshly installed system without libaio-devel.
Acked-by: Christian Borntraeger borntrae...@de.ibm.com
Another thing. Would it make sense to change the default to aio=native somewhen?
From what I can tell this seems to outperform aio=threads in most cases.
this seems a good idea to me, we are always changing
from threads to native in our installations
---
block/raw-posix.c | 11 ++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/block/raw-posix.c b/block/raw-posix.c
index 855febe..e09019c 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -519,7 +519,16 @@ static int raw_open_common(BlockDriverState *bs, QDict
*options,
future QEMU versions.\n,
bs-filename);
}
-#endif
+#else
+if (bdrv_flags BDRV_O_NATIVE_AIO) {
+error_printf(WARNING: aio=native was specified for '%s', but
+ is not supported in this build. Falling back to
+ aio=threads.\n
+ This will become an error condition in
+ future QEMU versions.\n,
+ bs-filename);
+}
+#endif /* !defined(CONFIG_LINUX_AIO) */
s-has_discard = true;
s-has_write_zeroes = true;
[Qemu-devel] [PATCH v2 1/2] raw-posix: warn about BDRV_O_NATIVE_AIO if libaio is unavailable
raw-posix.c silently ignores BDRV_O_NATIVE_AIO if libaio is unavailable.
It is confusing when aio=native performance is identical to aio=threads
because the binary was accidentally built without libaio.
Print a deprecation warning if -drive aio=native is used with a binary
that does not support libaio. There are probably users using aio=native
who would be inconvenienced if QEMU suddenly refused to start their
guests. In the future this will become an error.
Signed-off-by: Stefan Hajnoczi stefa...@redhat.com
---
block/raw-posix.c | 11 ++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/block/raw-posix.c b/block/raw-posix.c
index 855febe..e09019c 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -519,7 +519,16 @@ static int raw_open_common(BlockDriverState *bs, QDict
*options,
future QEMU versions.\n,
bs-filename);
}
-#endif
+#else
+if (bdrv_flags BDRV_O_NATIVE_AIO) {
+error_printf(WARNING: aio=native was specified for '%s', but
+ is not supported in this build. Falling back to
+ aio=threads.\n
+ This will become an error condition in
+ future QEMU versions.\n,
+ bs-filename);
+}
+#endif /* !defined(CONFIG_LINUX_AIO) */
s-has_discard = true;
s-has_write_zeroes = true;
--
2.4.3
