[Xen-devel] Re: 0/4 Xen Scheduling Groups - some microbenchmarks

["Mike D. Day" <ncmike@xxxxxxxxxx>]

On 10/05/07 17:33 -0400, Mike D. Day wrote:
> Scheduling Groups
>
> Scheduling groups provide the ability to combine domains into a group
> assocation. One domain is designated as the group master. The other
> domains are designated as group members. There may be only one master
> domain for each group, and one or more member domains. A single domain
> may be either a group master or group member, and never both at the
> same time.
I ran Rusty Russell's virtbench on xen-unstable without the scheduling
groups patches, and with the patches.

http://ozlabs.org/~rusty/virtbench/

Virtbench automatically creates four paravirtual guests and runs a
series of microbenchmarks, including some that test inter-guest
communication. I ran these benchmarks on an athlon x2 

Linux svm 2.6.18-xen #1 SMP Tue Apr 24 11:01:39 EDT 2007 x86_64 GNU/Linux

The results are mixed - the unpatched credit scheduler is faster on
some microbenchmarks and slower on others. 

Smaller == better

UNPATCHED RESULTS       

Bringing up machines..
Time for one context switch via pipe: 6082 (6014 - 6160)
Time for one Copy-on-Write fault: 5628 (5472 - 5783)
Time to exec client once: 581656 (562984 - 598656)
Time for one fork/exit/wait: 357625 (353625 - 365812)
Time to send 4 MB from host: 21401750 (20443000 - 31179250)
Time for one syscall via libc: 684 (684 - 685)
Time to walk linear 64 MB: 686312 (682437 - 689125)
Time to walk random 64 MB: 945250 (940750 - 948875)
Time for one outb PIO operation: 298 (298 - 300)
Time for two PTE updates: 5250 (5228 - 5264)
Time to read from disk (256 kB): 7879125 (5765500 - 18967062)
Time for one disk read: 25246 (24839 - 35062)
Time to send 4 MB between guests: 16729375 (14412437 - 30318562)
Time for inter-guest pingpong: 70152 (68960 - 104968)
Time to sendfile 4 MB between guests: 46993000 (16927000 - 380530000)
Time to receive 1000 1k UDPs between guests: 47102000 (11709000 - 3427813000)
mdday@svm:~/src/virtbench$                          

WITH SCHEDULING GROUP PATCHES

Bringing up machines..
Time for one context switch via pipe: 6117 (6016 - 6279)
Time for one Copy-on-Write fault: 5566 (5438 - 5740)
Time to exec client once: 584031 (569593 - 595093)
Time for one fork/exit/wait: 332406 (321125 - 350375)
Time to send 4 MB from host: 21453250 (20431500 - 29317750)
Time for one syscall via libc: 683 (683 - 690)
Time to walk linear 64 MB: 688312 (684000 - 691625)
Time to walk random 64 MB: 931125 (929250 - 933125)
Time for one outb PIO operation: 282 (282 - 292)
Time for two PTE updates: 5184 (5174 - 5204)
Time to read from disk (256 kB): 7963437 (5850375 - 17305687)
Time for one disk read: 25332 (24867 - 65437)
Time to send 4 MB between guests: 15529187 (13590187 - 34647875)
Time for inter-guest pingpong: 81570 (68687 - 98175)
Time to sendfile 4 MB between guests: 36325000 (16996000 - 503692000)
Time to receive 1000 1k UDPs between guests: 43529000 (10414000 - 228768000)


The only code that is in the fast patch is a conditional: 

static inline struct csched_dom *master_dom(struct csched_dom *d)
{
   if ( d->is_member )
       return d->master;
   return d;
}

I'm going to make a change to remove this conditional from the fast
path and retest. 

Mike

--
Mike D. Day
IBM LTC
Cell: 919 412-3900
Sametime: ncmike@xxxxxxxxxx AIM: ncmikeday  Yahoo: ultra.runner
PGP key: http://www.ncultra.org/ncmike/pubkey.asc

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