I''ve just pushed some changes to hg that seem to speed things up a bit for me. On one machine with 2 x dual core 2.4Ghz AMD cpu''s, testing with iperf from DomU to Dom0 I get: Windows (vcpus = 2) - ~500MBits/sec - ~66% cpu utilization (eg 100% on one, and 33% on the second cpu) Linux (vcpus = 1) - ~2200MBits/sec On another machine with 1 x dual core 1.8Ghz AMD cpu, testing as above I get: Windows (vcpus = 2) - ~65MBits/sec - ~100% cpu utilization (eg 100% on both cpu''s) Linux - can''t test as I don''t have any Linux DomU''s set up presently. I don''t think there is enough difference in raw CPU power to account for the 7x performance difference between the two physical machines... it must be something else. Anyway, on the second machine my performance is up from about 40MBits/sec so I think I''m making progress. James _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Sun, Mar 02, 2008 at 05:01:28PM +1100, James Harper wrote:> I''ve just pushed some changes to hg that seem to speed things up a bit > for me. > > On one machine with 2 x dual core 2.4Ghz AMD cpu''s, testing with iperf > from DomU to Dom0 I get: > Windows (vcpus = 2) - ~500MBits/sec - ~66% cpu utilization (eg 100% on > one, and 33% on the second cpu) > Linux (vcpus = 1) - ~2200MBits/sec >Was this Linux domU HVM (using PV drivers) or PV? In this box you have 4 physical cpus.. windows vm has 2 vcpus so your dom0 has 2 pcpus dedicated only for it..> On another machine with 1 x dual core 1.8Ghz AMD cpu, testing as above I > get: > Windows (vcpus = 2) - ~65MBits/sec - ~100% cpu utilization (eg 100% on > both cpu''s) > Linux - can''t test as I don''t have any Linux DomU''s set up presently. > > I don''t think there is enough difference in raw CPU power to account for > the 7x performance difference between the two physical machines... it > must be something else. >Hmm.. do these CPU''s have different sizes of caches? Then again it can''t cause that big difference.. Could it be some xen scheduling issue? You''re using 2 vcpus for windows, and in this second box you only have 2 pcpus.. and they''re both 100% used so no dedicated pcpus for dom0..> Anyway, on the second machine my performance is up from about > 40MBits/sec so I think I''m making progress. >Nice! -- Pasi _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
> > Was this Linux domU HVM (using PV drivers) or PV?I knew I''d forget something :) It''s a PV linux domain.> In this box you have 4 physical cpus.. windows vm has 2 vcpus so your dom0 > has 2 pcpus dedicated only for it..Well... there are 10 other DomU''s on the machine too, but none of them work particularly hard (which is why virtualisation is such a good thing!).> > On another machine with 1 x dual core 1.8Ghz AMD cpu, testing as above I > > get: > > Windows (vcpus = 2) - ~65MBits/sec - ~100% cpu utilization (eg 100% on > > both cpu''s) > > Linux - can''t test as I don''t have any Linux DomU''s set up presently. > > > > I don''t think there is enough difference in raw CPU power to account for > > the 7x performance difference between the two physical machines... it > > must be something else. > > > > Hmm.. do these CPU''s have different sizes of caches? Then again it can''t > cause that big difference..Probably yes they do.> Could it be some xen scheduling issue? You''re using 2 vcpus for windows, > and in this second box you only have 2 pcpus.. and they''re both 100% > used so no dedicated pcpus for dom0..There is probably something in that. The thing that is bugging me is the amount of CPU required... I am implementing checksum offload right now which might cut some of it down. I wonder if HVM supports page flipping as opposed to page copying. I don''t know much about page flipping but if it is what I think it is then we could actually implement zero copy. James _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Sun, Mar 02, 2008 at 11:57:16AM +0200, Pasi Kärkkäinen wrote:> > Could it be some xen scheduling issue? You''re using 2 vcpus for windows, and > in this second box you only have 2 pcpus.. and they''re both 100% used so no > dedicated pcpus for dom0.. >Maybe try windows with vcpus=1 in this box.. then you should have the other pcpu only for dom0 and see if that makes difference.. -- Pasi _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Sun, Mar 02, 2008 at 12:02:16PM +0200, Pasi Kärkkäinen wrote:> On Sun, Mar 02, 2008 at 11:57:16AM +0200, Pasi Kärkkäinen wrote: > > > > Could it be some xen scheduling issue? You''re using 2 vcpus for windows, and > > in this second box you only have 2 pcpus.. and they''re both 100% used so no > > dedicated pcpus for dom0.. > > > > Maybe try windows with vcpus=1 in this box.. then you should have the other > pcpu only for dom0 and see if that makes difference.. >You could also try setting xen credit scheduler weights for domains.. maybe giving more cpu for dom0 (bigger weigth) ? The big question is why all cpu is used on this second box when iperf is running on windows.. How big was the CPU usage on Linux PV domU ? -- Pasi _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users