[Devel] Re: [Vserver] Re: Container Test Campaign

[Herbert Poetzl]

On Wed, Jul 12, 2006 at 06:31:25PM +0200, Clément Calmels wrote:
> Le mardi 11 juillet 2006 à 13:18 +0400, Kirill Korotaev a écrit :
> > > Some updates on
> > > http://lxc.sourceforge.net/bench/
> > > 
> > > New design, results of the stable version of openvz added, clearer
> > > figures.
> > > 
> > 
> > 1. are 2.6.16 OVZ results still for CFQ disk scheduler?
> 
> This tests are currently in progress... for the moment, it seems that
> the anticipatory io scheduler improves performance a lot.
> 
> > 2. there is definetely something unclean in your testing as
> >   vserver and MCR makes dbench faster than vanilla :))

that's not really unusual ...

> Couldn't some test be faster inside a container than with a Vanilla? 

yes, they definitely can, and some very specific ones
are constantly faster regardless of how many tests
and/or setups you have ...

> For example if I want to dump all files in /proc, obviously inside a
> light container it will be faster because /proc visibility is limited
> to the container session. Just to be clear:
> 
> r3-21:~ # find /proc/ | wc -l
> 4213
> r3-21:~ # mcr-execute -j1 -- find /proc/ | wc -l
> 729
> 
> I'm not sure and I'm still investigating. I'm now adding Oprofile to all
> tests to have more information. If you know technical reasons that imply
> different results, let me know. Help welcome!

yes, the 'isolation' used in Linux-VServer already
gave that 'at first glance' strange behaviour that
some tests are 'faster' inside a guest than on the
real/vanilla system, so for us it is not really new
but probably it is still confusing, here are a few
reasons _why_ some tests are better than the 'original'

 - structures inside the kernel change, relations
   between certain structures change too, some of
   those changes cause 'better' behaviour, just
   because cache usage or memory placement is different

 - many checks walk huge lists to find a socket or
   process or whatever, some of them use hashes to
   speed up the search, the lightweight guests often
   provide faster access to 'related' structures

 - scheduler and memory management are tricky beasts
   sometimes it 'just happens' that certain operations
   and/or sequences are faster than other, although
   they give the same result

HTC,
Herbert

> -- 
> Clément Calmels <clement.calmels at fr.ibm.com>
> 
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