Re: AIO requests may be disordered by Qemu-kvm iothread with disk cache=writethrough, Bug or Feature?

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Thu, Oct 08, 2015 at 07:59:56PM +0800, charlie.song wrote:
>     We recently try to use Linux AIO from guest OS and find that the IOthread mechanism of Qemu-KVM will reorder I/O requests from guest OS 
> even when the AIO write requests are issued from a single thread in order. This does not happen on the host OS however.

I think you are describing a situation where a guest submits multiple
overlapping I/O requests at the same time.

virtio-blk does not guarantee a specific request ordering, so the
application needs to wait for request completion if ordering matters.

io_submit(2) also does not make guarantees about ordering.

Stefan
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html



[Index of Archives]     [KVM ARM]     [KVM ia64]     [KVM ppc]     [Virtualization Tools]     [Spice Development]     [Libvirt]     [Libvirt Users]     [Linux USB Devel]     [Linux Audio Users]     [Yosemite Questions]     [Linux Kernel]     [Linux SCSI]     [XFree86]
  Powered by Linux