[Samba] Re: samba on quad core vs dual core

[Jeremy Allison]

On Tue, Dec 09, 2008 at 03:17:53PM -0500, Andy Liebman wrote:
>
>> Samba will use all the cores you can give it - so long as
>> you have at least more clients than cores.
>>
>> Jeremy.
>>   
> While I have found that to be true in my environment, I have also found  
> that MOST smbd's end up on Core 0 MOST of the time.  This is true even  
> if I am hammering a 10 Gigabit network adapter (i.e., sending out 700  
> MB/sec via Samba distributed to 30 users), with total CPU utilization  
> only about 70 percent of one core.
>
> Maybe this is optimal behavior.  I tried to start a thread on this  list  
> a while back about understanding what WOULD be optimal, and nobody had  
> much to say.
>
> I think it would be an interesting discussion. NFS seems to make use of  
> multicores in a more even way. That doesn't mean the NFS behavior is  
> better.

smbd is a userspace process, so we don't do anything
clever w.r.t. distributing ourselves across cores, only
let the OS do it's stuff.

I'm guessing in your case you're seeing the effects
of the OS accumulating the network interrupt traffic
on the one processor that's handling that card.

Jeremy.