Re: 2.6.1 and irq balancing

[Bill Davidsen]

Nakajima, Jun wrote:

> 2.6 kernels don't need a patch to it as far as I understand. Are you
> saying that with significant amount of load, you did not see any
> distribution of interrupts? Today's threshold in the kernel is high
> because we found moving around interrupts frequently rather hurt the
> cache and thus lower the performance compared to "do nothing". Can you
> try to create significant load with your network (eth0 and eh1) and see
> what happens? 

How much is significant? The term doesn't really help much. I will say 
that with one NIC taking 120MB/sec of data to a TB database and copying 
to two other machine (~220MB)  my interrupts got up in in the 5k-12k 
range with essentially CPU0 doing the work, some few percent going to CPU2.

I'm not sure this is a problem in any way, but some serious load is 
needed to trigger sharing, if indeed the NIC was the source of the ints 
on CPU2.

2x Xeon-2.4GHz, HT enabled. "CPU2" from memory, it was the other 
physical CPU, not another sibling. Worked fine, didn't break, don't 
regard it as a problem.

--
bill davidsen <davidsen@xxxxxxx>
  CTO TMR Associates, Inc
  Doing interesting things with small computers since 1979
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