2 x quad-core system is slower that 2 x dual core on FreeBSD

Kris Kennaway kris at FreeBSD.org
Tue Nov 20 01:50:51 PST 2007

Alexey Popov wrote:
> Hi.
> Kris Kennaway wrote:
>>>>> CPU states:  9.5% user,  0.0% nice, 82.0% system,  0.5% interrupt,  
>>>>> 8.0% idle
>>>> A wild idea that might not help: try reducing kern.hz in loader.conf to
>>>> something like 100 and see if something significant changes.
>>> Now it runs with hz=100, number of context switches became ~ 2 times
>>> less, but still there's 90% system CPU load (see attach).
>> System CPU usage doesn't tell you anything by itself, you need to look 
>> at how much work the system is actually doing (pages served/second, or 
>> whatever).  For example, when your kernel is getting more work done, 
>> system CPU usage will also be higher.
> Usually on PHP backends slow PHP code eats most of the CPU time. I have 
> %user much bigger than %system in CPU states.
> But now %system is much bigger than %user and I can conclude that on 
> 8-core server FreeBSD consumes more CPU time than PHP.

That is one possibility, but you still need to look at the actual 
throughput on these machines before making conclusions about which is 
performing better.  Can you please provide those numbers for 6.x, 7.x 
with ULE and 4BSD on the 4-core and 8-core systems?


More information about the freebsd-stable mailing list