Re: XEN 4.11 and 9.99.48 DOMU performance

[Greg Troxel <gdt%lexort.com@localhost>]

I wonder if the issue is that the dom0 is single threaded, serializing
all the IO.

Have you done dd bs=1m from the dom0 raw disk, the dom0 backing file,
and the domU ('raw disk')?   I used to see X, 0.9X, and (0.9)^2 X, ish,
on somewhat old Xen and older NetBSD.

I would run "systat vmstat" in the domU, to see the disk busy fraction
and transfer rate.

I also wonder if there is some sort of fsync in the domU leading to
virtual FUA leading to fsync in the dom0 going on.