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Re: [Xen-devel] [PATCH][RFC] open HVM backing storage with O_SYNC

  • To: xen-devel@xxxxxxxxxxxxxxxxxxx
  • From: Rik van Riel <riel@xxxxxxxxxx>
  • Date: Fri, 28 Jul 2006 16:21:29 -0400
  • Delivery-date: Fri, 28 Jul 2006 13:21:54 -0700
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>

Rik van Riel wrote:
Rik van Riel wrote:

Any comments on this patch?

I got some comments from Alan, who would like to see this behaviour
tunable with hdparm from inside the guest.  This requires larger
qemu changes though, to be specific an ->fsync callback into each
of the backing store drivers, so that is something for the qemu
mailing list.

Considering the AIO-based development going on in the qemu community,
I think we should stick with the O_SYNC band-aid.  The idea Alan
described would just be a fancier band-aid.

The current bottleneck seems to be that MAX_MULT_COUNT is only 16.

Upon closer inspection of the code, this seems to not be the case for LBA48 transfers.

"Debugging is twice as hard as writing the code in the first place.
Therefore, if you write the code as cleverly as possible, you are,
by definition, not smart enough to debug it." - Brian W. Kernighan

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