On 05/24/2017 05:20 PM, Alberto Garcia wrote:
On Tue 23 May 2017 04:36:52 PM CEST, Eric Blake wrote:
here's a patch series that rewrites the copy-on-write code in the
qcow2 driver to reduce the number of I/O operations.
And it competes with Denis and Anton's patches:
https://lists.gnu.org/archive/html/qemu-devel/2017-05/msg04547.html
What plan of attack should we take on merging the best parts of these
two series?
I took a look at that series and unless I overlooked something important
it seems that there's actually not that much overlap. Denis and Anton's
series deals with cluster preallocation and mine reduces the number of
I/O operations when there's a COW scenario. Most of my modifications are
in the peform_cow() function, but they barely touch that one.
I think we can review both separately, either of us can rebase our
series on top of the other, I don't expect big changes or conflicts.
Berto
I agree; as mentioned we have similar patches and they don't conflict much.
We noticed a performance regression on HDD though, for the presumably
optimized case (random 4k write over a large backed image); so the
patches were put on hold.
SSD looked fine though.
/Anton
