cpuinfo, bogomips and duo core

[Gordan Bobic]

On 12/02/2013 00:42, Reindl Harald wrote:
>
>
> Am 12.02.2013 01:17, schrieb Robert Moskowitz:
>>
>> On 02/11/2013 06:07 PM, Reindl Harald wrote:
>>>
>>> Am 11.02.2013 23:43, schrieb Robert Moskowitz:
>>>> Do I have this right?
>>>>
>>>> since on a duo core system, /proc/cpuinfo reports both cores and a bogomips number for each, that number is the
>>>> value for a core.  Thus 'in theory' the bogomips for the unit is the sum of the two values (the same in every duo
>>>> core I have seen)
>>> practically i would say this value is hmm useless
>>>
>>> is it hardcoded in the CPU?
>>> is it measured?
>>>
>>> if it is measured at which moment of time
>>> which stepping had the CPU at the moment :-)
>>
>> I realize it is rather relative, but it helps me keep my various systems classified, like system 1 is probably
>> twice the speed of system 2 (given same # of cores and memory)
>
> not really :-)
>
> home machine (16 GB)
> model name: Intel(R) Core(TM) i7-3770 CPU @ 3.40GHz
> bogomips: 6784.31
>
> production VMware guest (10 GB)
> model name      : Intel(R) Xeon(R) CPU E5-2640 0 @ 2.50GHz
> bogomips        : 4987.50
>
> under real load the XEON is so much faster even
> with the virualization overhead which is small
> these days but still exists

Small as in un-noticeable if your VMs are largely idling. Not that small 
if you intend to push the hardware to it's actual limits. On a Core2 
class machine, the best hypervisors manage to do it with about a 25% 
performance drop. Many do worse.

http://www.altechnative.net/2012/08/04/virtual-performance-part-1-vmware/

> i have seen the XEON machine with a Load of 140 while a massive DDOS was running
> with ten thousands of connections and 100Mbit incoming traffic from always the
> same request on a mysql-driven website and ssh/lsof/ps aux was as fast as it would
> be idle, on the home-machine with a load over 40 you are done

It's not that clear cut - it depends on where the DOS bottlenecks the 
system. If you have a web server being DOS-ed and it's waiting for 
responses from MySQL which is on a different server, then yes, you'll 
have a very high load and very low CPU usage since most of the httpds 
are waiting for a response from the DB. Since CPU usage is low, the 
machine itself will be very responsive if you ssh into it. The web 
response, may well not be.

Gordan