[netperf-talk] CPU utilization & tickless kernels?

[Andrew Gallatin]

On 12/07/12 17:26, Rick Jones wrote:

> Ostensibly, the 2.6.38 kernel used above is tickless:
> 
> raj at tardy:~$ uname -a
> Linux tardy 2.6.38-16-generic #67-Ubuntu SMP Thu Sep 6 17:58:38 UTC 2012
> x86_64 x86_64 x86_64 GNU/Linux
> raj at tardy:~$ grep HZ /boot/config-2.6.38-16-generic
> CONFIG_RCU_FAST_NO_HZ=y
> CONFIG_NO_HZ=y
> CONFIG_HZ_100=y
> # CONFIG_HZ_250 is not set
> # CONFIG_HZ_300 is not set
> # CONFIG_HZ_1000 is not set
> CONFIG_HZ=100
> CONFIG_MACHZ_WDT=m
> 
> and while my investigation wasn't exhaustive, my tests like those above
> seemed to show agreement between netperf and vmstat - it was showing
> about 79% idle in the overall.
> 
> You mentioned a "slow" system with 10 GbE networking.  In the past, at
> least a couple of platforms have had issues with not counting interrupt
> time accurately.  That would be a bigger problem when the interrupt time
> was a larger percentage of the total.  Any chance something along those
> lines is happening to you?

I'll try a different kernel to try to rule this out..
Maybe dtrace profile scripts will start working too :)

Thanks,

Drew