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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