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.