Re: [libvirt] PATCH: Disable QEMU drive caching
Anthony Liguori wrote:
Mark McLoughlin wrote:
And let's take a step back too. If people are really concerned about
this point, let's introduce a sync=on option that opens the image with
O_SYNC. This will effectively make the cache write-through without
the baggage associated with O_DIRECT.
I'm starting to slowly convince myself we should always open files with
O_SYNC. Barriers should just force ordering within the thread pool.
posix-aio has no interface for this but we could create one with our own
thread pool implementation.
Ryan: could you give the following patch a perf-run so we can see how
this would effect us?
Thanks,
Anthony Liguori
While I object to libvirt always setting cache=off, I think sync=on
for IDE and SCSI may be reasonable (you don't want it for virtio-blk
once we implement proper barriers with fdatasync I think).
Regards,
Anthony Liguori
> Cheers,
> Mark.
>
>
Attachments:
- o_sync.patch (text/x-patch — 411 bytes)