Re: [Xen-users] vcpu performance : 1 vcpu for all guets or 4 vpcu ?

[Tim Post <tim.post@xxxxxxxxxxx>]

On Mon, 2007-06-11 at 06:59 +0200, Pascal wrote:
> Hi Tim 
> 
> Thanks a lot for this long answer  ;)
> 
> We've done some tests and it seems good to have 1 core reserved for
> dom0, the other balancing through vcpu to all guests.
> 
Or at least 1/2 of one core. It really depends on the I/O needs of your
guests.

I have one server that has nearly 50 load balancing guests running on
it. It uses software that never touches disk once resident and running.
It could easily hold 50 more. 

> Maybe one more question.

Sure :)

> We are working on a solution to count the guest trafic by month and
> maybe to limit the bandwidth used by every guests.
> 
> For the trafic, we are currently trying to play with rrdtool + a
> script that does something like this and write these data in a mysql
> database :
> ifconfig -a vif34.0 | grep 'RX bytes' | cut -d : -f 2 | cut -d ' ' -f
> 1
> 
> For the bandwidth limit there is of course TC 
> 
> Just by curiosity, did you implement one of these solutions ?
> Do you have others idea, is there some control panel or existing
> script which do that ?
> 
> Thanks
> 
> 
> Pascal

Try reading from /proc/net/dev directly. That pipe invokes many things
that allocate much more memory than is actually needed.

Line editors have *no* idea how big stdin is going to be, so they need
to allocate a lot of memory that is just wasted for 15 - 30 mins for
such a menial task.

Ideally, back end stuff on dom-0 tries its best not to do that, since
contiguous chunks of RAM can be hard to come by in such small spaces.

Ideally, such a solution would e-mail (or otherwise notify) your clients
when they reached about 80% of that quota. Floats in simple shell
scripts are a pain, I recommend you use C or python. Bash is very
bloated for this particular use. Every invocation of /bin/sh puts a
gazillion things in memory you'll never use. You could try other
bourne-ish shells, but most of them don't support arrays which you'd
want for this.

If you don't know python or C, try grawk.

http://dev1.netkinetics.net/hg/utils.hg/grawk.c

.. in place of grep / awk / cut

grawk "^\ \ eth0" '$2,$9' /proc/net/dev

produces the two values I think that you want with a single invocation. 

Of course, substitute eth0 for the vifname. That repo also contains non
blocking highly abuse-able http and ftp services you may find of use.

Please reply-to-all or CC the list so everyone can benefit from the
answers to your questions :) 

Best,
--Tim



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