[CentOS] measuring kernel speed

[Les Mikesell]

On 5/10/2010 8:56 AM, Ross Walker wrote:
>
>>
>> Would this also be suitable for testing efficiency loss from running
>> under
>> VMware or other virtualization methods?
>
> No because oprofile and latencytop's point of reference is just the
> running kernel and doesn't factor in CPU allocations, network/disk
> virualization/para-virtualization, bandwidth allocations, etc.
>
> Efficiency loss is a slippery slope and VERY configuration dependant.
>
> I have seen VMs perform better than physical machines and I have seen
> them perform worse, sometimes on the same physical host!
>
> Go with the "user experience" indicator (assuming it is properly
> configured for the workload). Does it seem fast? Then it's fast. Does
> it seem slow? Then it is slow.

Realistically, VM performance is going to depend mostly on how much 
contention you have between guests for common resources especially if 
you overcommit them.  But, I'd like to have some idea of how much effect 
running under VMware ESXi would have for a single guest, compared to 
running directly on the hardware.  If there's not a big loss (and it 
doesn't 'feel' like there is), I'd consider this worthwhile for servers 
doing oddball things where its not worth the trouble to script a 
re-install for every little app someone might have running as a means to 
deal with the usual pain of moving a working system to different 
hardware.  Plus, if there is extra capacity you can bring up another 
virtual machine or test the next version almost for free, and you get an 
almost-hardware level kvm too (after the base install works and you have 
an IP address...).  I'd just like to have a more objective measure of 
what it costs in performance.

-- 
   Les Mikesell
     lesmikesell at gmail.com