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From: | Denis V. Lunev |
Subject: | Re: [Qemu-devel] [PATCH v2 1/2] raw-posix: warn about BDRV_O_NATIVE_AIO if libaio is unavailable |
Date: | Thu, 23 Jul 2015 13:11:57 +0300 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.8.0 |
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 <address@hidden>had that myself on a freshly installed system without libaio-devel. Acked-by: Christian Borntraeger <address@hidden> 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; |
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