Re: inaccurate cpu idle time from top command

[Fred Fan]

Hi cocala:
    I have met same issue. And we found the total utilization
count(added by idle's utilization) is not 100% in detail processes
information fields.
   best Regards
Fred

2009/7/24 cocala <syy.wxd@xxxxxxxxx>:
> I saw one commit "3209ada8285a9fa6ab8f7a731d54031ec884c745 - sched: account
> system time properly"
> This commit is to take into account timer IRQ interrupting the idle task
> servicing a hard or soft irq.
>
> If a softirq is started in a tick, all the time in the tick will be counted
> as soft irq time even most time in the tick is idle.
> In our use case, one jiffy is 10ms and the 1G net driver will generate many
> software irq, so the "top" command will show high softare irq time and cpu
> idle time approaches to zero.
> If I change the jiffy to 1ms, the "top" command shows much higher cpu idle
> time. I think this algorithm is also not fair for some cases.
>
> Is there any better way to count the softare irq time?
>
> Thanks
> cocala
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