Re: [Xen-devel] Can't always start 32 bit domains after 64 bit domains

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

On Mon, 2016-11-21 at 13:06 -0800, Sarah Newman wrote:
> On 11/21/2016 11:37 AM, Sarah Newman wrote:
> > 
> > If that's the reason not all the higher memory is being used first:
> > is a potential workaround to pin 64 bit domains to the second
> > physical core on
> > boot, and 32 bit domains to the first physical core on boot, and
> > then change the allowed cores with 'xl vcpu-pin' after the domain
> > is loaded?
> 
> Free memory on a test server with no domains:
> node:    memsize    memfree    distances
>    0:    148480     142983      10,21
>    1:    147456     144645      21,10
> 
> Free memory booting 116 256M 64-bit domains, limited to cpus='all,^0-
> 1' on boot:
> node:    memsize    memfree    distances
>    0:    148480     128416      10,21
>    1:    147456     129669      21,10
> 
> Free memory booting 116 256M 64-bit domains, limited to cpus='12-23'
> on boot:
> node:    memsize    memfree    distances
>    0:    148480     143397      10,21
>    1:    147456     114693      21,10
> 
> This looks like a viable workaround. Where should I document it?
> 
It's documented in here (although, the text can be improved a bit, I
think)... look for 'cpus' and 'cpus_soft' within the page:
https://xenbits.xen.org/docs/unstable/man/xl.cfg.5.html

A more clear mention to using "all" can perhaps be added to the wiki
pages I listed in my other email.

However, what I think is totally missing, is any documentation about
the fact that, in use cases like yours, domain creation should be done
in a certain order, for what reasons, which order is that, and the fact
that NUMA placement may interfere.

I'm not sure where and how to properly document all this [adding Lars],
but I'd say it probably deserves a dedicated wiki page.

Thoughts?

Regards,
Dario
-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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