Re: [Xen-users] Release 0.8.9 of GPL PV drivers for Windows

["Todd Deshane" <deshantm@xxxxxxxxx>]

On Tue, May 6, 2008 at 11:05 PM, jim burns <jim_burn@xxxxxxxxxxxxx> wrote:
> On Tuesday May 06 2008 03:21:29 am Pasi Kärkkäinen wrote:
>
> > OK. I think measuring pv domU is worth trying too :)
>
>  Ok, let's try a few things. Repeating my original 0.8.9 numbers, with the new
>  processor:
>
>
>  pattern 4k, 50% read, 0% random
>
>  dynamo on?  |   io/s   |  MB/s  | Avg. i/o time(ms} | max i/o time(ms) | %CPU
>  domu w/gplpv|   501.7  |   1.96 |        2.90       |       0          | 
> 31.68
>  domu w/qemu |   187.5  |   0.73 |        5.87       |       0          | 
> 29.89
>  dom0 w/4Gb  |  1102.3  |   4.31 |        0.91       |      445.5       |  0
>  dom0 w/4Gb  |  1125.8  |   4.40 |        0.89       |      332.1       |  0
>  (2nd dom0 numbers from when booted w/o /gplpv)
>
>  pattern 32k, 50% read, 0% random
>
>  domu w/gplpv|   238.3  |   7.45 |        4.09       |        0         | 
> 22.48
>  domu w/qemu |   157.4  |   4.92 |        6.35       |        0         | 
> 20.51
>  dom0 w/4Gb  |    52.5  |   1.64 |       19.05       |     1590.0       |  0
>  dom0 w/4Gb  |    87.8  |   2.74 |       11.39       |     1286.4       |  0
>
>  Now, that was with all workers running on domu and dom0 simultaneously. Let's
>  try one at a time. On hvm w/gplpv, first the 4k pattern, then later the 32k
>  pattern, with dom0 using the 'idle' task:
>
>   4k pattern |  1026.6  |   4.01 |       39.37       |       0          | 
> 49.70
>  32k pattern |   311.1  |   9.72 |       45.33       |       0          | 
> 26.21
>
>  Now test dom0, with the hvm running the 'idle' task:
>
>   4k pattern |  1376.7  |   5.38 |        0.73       |      365.7       |  0
>  32k pattern |   165.9  |   5.19 |        6.02       |      226.6       |  0
>
>  As expected, all numbers are significantly faster. Compare this to 'dd'
>  creating the 4GB /iobw.tst file on dom0 at a 22MB/s rate.
>
>  Now, to test a fedora pv, since space is tight on my fedora xen server, I
>  just 'xm block-attach'-ed dom0's /iobw.tst as a new partition on the domu,
>  and in the domu, did mkfs, mount, and created a new /iobw.tst on that
>  partition. Results:
>
>   4k pattern |  1160.5  |   4.53 |        0.86       |      247.1       |  0
>  32k pattern |   284.1  |   8.88 |        3.52       |      326.4       |  0
>
>  The numbers are very similar to the hvm, including the 32k pattern being
>  faster than dom0, which you pointed out is due to caching. This compares
>  to 'dd' creating the 3.7GB iobw.tst on the mounted new partition at an 18MB/s
>  rate.
>
>
>  > Configure dom0 for 1 vcpu and domU for 1 vcpu and pin the domains to have a
>  > dedicated core. This way you're not sharing any pcpu's between the domains.
>  > I think this is the "recommended" setup from xen developers for getting
>  > maximum performance.
>  >
>  > I think the performance will be worse when you have more vcpus in use than
>  > your actual pcpu count..
>
>  Now I rebooted dom0, after editing xend-config.sxp to include '(dom0-cpus 
> 1)',
>  and then did the following pins:
>
>  [576] > xm create winxp
>  Using config file "/etc/xen/winxp".
>  Started domain winxp
>  root@Insp6400 05/06/08 10:32PM:~
>  [577] > xm vcpu-pin 0 all 0
>  root@Insp6400 05/06/08 10:32PM:~
>  [578] > xm vcpu-pin winxp all 1
>  root@Insp6400 05/06/08 10:32PM:~
>  [579] > xm vcpu-list
>
> Name                               ID  VCPU   CPU State   Time(s) CPU Affinity
>  Domain-0                             0     0     0   r--     228.7 0
>  Domain-0                             0     1     -   --p      16.0 0
>  winxp                                5     0     1   r--      36.4 1
>
>  Note I also had to set vcpus=1, because with two, I was again getting that
>  extremely sluggish response in my hvm.
>
>  Going back to simultaneous execution of all workers, to compare against the
>  numbers at the top of this post, I got:
>
>
>  pattern 4k, 50% read, 0% random
>
>  dynamo on?  |   io/s   |  MB/s  | Avg. i/o time(ms} | max i/o time(ms) | %CPU
>  domu w/gplpv|   286.4  |   1.12 |        3.49       |      564.9       | 
> 36.97
>  dom0 w/4Gb  |  1173.9  |   4.59 |        0.85       |      507.3       |  0
>
>
>  pattern 32k, 50% read, 0% random
>
>  domu w/gplpv|   217.9  |   6.81 |        4.57       |     1633.5       | 
> 22.93
>  dom0 w/4Gb  |    63.3  |   1.97 |       15.85       |     1266.5       |  0
>
>  which is somewhat slower. Recommendations of the xen developers aside, my
>  experience is that allowing xen to schedule any vcpu on any pcpu is most
>  efficient.
>

I think that your experience (allowing Xen to do the scheduling itself is most
efficient and only try to tweak the scheduling in very special cases and/or you
really know what you are doing) should be considered conventional wisdom.

Can you refresh me on the recommendations of the Xen developers that you
are referring to?

Thanks,
Todd

>
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