Re: [Qemu-devel] [PATCH v2] rbd: add an asynchronous flush

[Kevin Wolf]

Am 11.04.2013 um 19:19 hat Josh Durgin geschrieben:
> On 04/11/2013 01:48 AM, Kevin Wolf wrote:
> >Am 11.04.2013 um 10:02 hat Stefan Hajnoczi geschrieben:
> >>On Wed, Apr 10, 2013 at 07:03:39AM -0700, Josh Durgin wrote:
> >>>On 04/02/2013 07:10 AM, Kevin Wolf wrote:
> >>>>Am 29.03.2013 um 21:03 hat Josh Durgin geschrieben:
> >>>>>The existing bdrv_co_flush_to_disk implementation uses rbd_flush(),
> >>>>>which is sychronous and causes the main qemu thread to block until it
> >>>>>is complete. This results in unresponsiveness and extra latency for
> >>>>>the guest.
> >>>>>
> >>>>>Fix this by using an asynchronous version of flush.  This was added to
> >>>>>librbd with a special #define to indicate its presence, since it will
> >>>>>be backported to stable versions. Thus, there is no need to check the
> >>>>>version of librbd.
> >>>>
> >>>>librbd is linked dynamically and the version on the build host isn't
> >>>>necessarily the same as the version qemu is run with. So shouldn't this
> >>>>better be a runtime check?
> >>>
> >>>While we discuss runtime loading separately, would you mind taking this
> >>>patch as-is for now?
> >>
> >>Hi Josh,
> >>I'm happy with Patch v3 1/2.  Does that work for you?
> >
> >Only patch 1/2 would add dead code as .bdrv_aio_flush would never be
> >called. I think we should rather take v1 of the series then, with the
> >#ifdefs at build time.
> 
> Yes, that would be a problem with only v3 1/2. v2 of the original
> series is fine, but v1 was accidentally missing a hunk. To be clear,
> I think just http://patchwork.ozlabs.org/patch/232489/ would be good.

Yes, sorry, I should have checked before posting this. v2 I meant.

Kevin