Re: [Qemu-devel] [PATCH 1/2] linux aio: support flush operation

[Frediano Ziglio]

Il giorno 27/lug/2011, alle ore 20:31, Christoph Hellwig <address@hidden> ha 
scritto:

> Did you test this at all?
> 

Yes! Not at kernel level :-)
Usually I trust documentation and man pages.

> On Wed, Jul 27, 2011 at 08:25:25PM +0200, Frediano Ziglio wrote:
>> +    case QEMU_AIO_FLUSH:
>> +        io_prep_fdsync(iocbs, fd);
>> +        break;
> 
> Looks great, but doesn't work as expected.
> 
> Hint: grep for aio_fsync in the linux kernel.
> 

Thanks. I'll try to port misaligned access to Linux AIO. Also I'll add some 
comments on code to avoid somebody do the same mistache I did.
Mainly however -k qemu-img and aio=native in blockdev options are silently 
ignored if nocache is not enabled. Also I notice that combining XFS, Linux AIO, 
O_DIRECT and O_DSYNC give impressive performance but currently there is no way 
to specify all that flags together cause nocache enable O_DIRECT while O_DSYNC 
is enabled with writethrough.

Frediano