Re: [Xen-users] Give dom0 2 pinned vcpus, but share one with domU

[jumperalex <alex@xxxxxxxxxxxxxx>]

wow, I made the Todo list in my first thread :O  I'm not sure if that is an
honor or a scarlet letter?

Anyway thanks for the tips.  So apparently we (aka unRaid users) have had
some problems with cpu stalling when not pinned.  But we are also on kernel
3.10.24 (with an update to 3.14 coming soon) and Xen 4.3 (4.4 also coming
soon) so I won't go asking for help with that specifically.  But it is
another reason I had choosen to pin early on.

In any case thanks for the tips.  I'm probably going to just open all doms
to all vcpus do some testing and see what happens.  If I start seeing cpu
stalls I'll see if playing with credit scheduler helps.  

re: rsync ... it looks like "-asP --inplace" is giving us the best
performance which probably isn't new.  Thanks also for addressing that.


Ian Campbell-10 wrote
> On Tue, 2014-05-20 at 05:22 -0700, jumperalex wrote:
>> > How about NOT pinning / Why am I pinning?
>> 
>> In short because of this
>> http://wiki.xen.org/wiki/Xen_Project_Best_Practices#Dedicating_a_CPU_core.28s.29_only_for_dom0
>> I'm just doing what I'm told :O  But I'm obviously open to suggestion.
> 
> This is mentioned in http://wiki.xen.org/wiki/Tuning#Dom0_VCPUs and
> http://wiki.xen.org/wiki/Tuning#Vcpu_Pinning too. It does say "might"
> and "can", perhaps even those are a bit strong. Pinning is one tool in
> the performance tuning arsenal but it is very workload dependent on
> whether it will help or hurt (and it can be a lot in either direction).
> 
> I've made a note of this on
> http://wiki.xen.org/wiki/Xen_Document_Days/TODO . Hopefully someone who
> knows this tuning stuff better than I will improve things at some point.
> 
> Ian.





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