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;
