viostor bad write performance compared to older version

[Tim-Co]

When using version 1.094, 1.02, or 1.110 of viostor.sys I get less than half the write performance compared to using version 1.074 and version 1.81.

I'm Windows 2012 R2 and Windows 8.1 instances with a host using qemu-kvm version 1.5.3 and a ceph version 0.94.3 storage backend. I have cache=writeback and rbd cache enabled as well.

When using 1.74 of viostor.sys I get the following numbers using crystaldiskmark

Test	Read MB/s	Write MB/s
Seq Q32T1	716.9	120.9
4K Q32T1	58.04	9.606
Seq	321.0	112.8
4K	5.697	11.88

When using 1.110 I get

Test	Read MB/s	Write MB/s
Seq Q32T1	820.4	41.78
4K Q32T1	64.08	0.543
Seq	448.3	38.80
4K	7.474	0.109

Version 1.094 and 1.102 have similar write numbers to 1.110

[vrozenfe]

Thank you for reporting this problem.

It's a know problem. For more information please visit
the following link:
https://bugzilla.redhat.com/show_bug.cgi?id=1238812

Best regards,
Vadim.

[vrozenfe]

We have completed performance testing cycle some time ago.
(https://bugzilla.redhat.com/show_bug.cgi?id=1023894#c11)
No issues have been found so far.

Closing this issue for now.

If anyone experiences the similar problems when running the resent virtio block or scsi drivers on the latest stable upstream qemu, please feel free to reopen it again or open a new issue.

Vadim.