On 10/15/2009 07:54 AM, Anthony Liguori wrote:
Christoph Hellwig wrote:
On Thu, Oct 15, 2009 at 01:56:40AM +0900, Avi Kivity wrote:
Does virtio say it has a write cache or not (and how does one say it?)?
Historically it didn't and the only safe way to use virtio was in
cache=writethrough mode.
It didn't say? So it's up to the default, which is what?
Which should be the default on Ubuntu's kvm that this report is
concerned with so I'm a bit confused.
Avi's patch is a performance optimization, not a correctness issue?
If filesystems do drain by default, it should be a no-op on
cache!=writeback.
However if lseek(0); write(1); fdatasync(); are faster than disk speed,
then something in our assumptions has to be wrong.
--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.
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