On 01.09.2016 14:57, Eric Dumazet wrote:
> On Thu, 2016-09-01 at 14:38 +0200, Jesper Dangaard Brouer wrote:
>
>> Correction, on the server-under-test, I'm actually running RHEL7.2
>>
>>
>>> How do I verify/check if I have enabled a cpu-cgroup?
>>
>> Hannes says I can look in "/proc/self/cgroup"
>>
>> $ cat /proc/self/cgroup
>> 7:net_cls:/
>> 6:blkio:/
>> 5:devices:/
>> 4:perf_event:/
>> 3:cpu,cpuacct:/
>> 2:cpuset:/
>> 1:name=systemd:/user.slice/user-1000.slice/session-c1.scope
>>
>> And that "/" indicate I've not enabled cgroups, right?
>>
>
> In my experience, I found that times displayed by top are often off for
> softirq processing.
>
> Before applying my patch, top shows very small amount of cpu time for
> udp_rcv and ksoftirqd/0 , while obviously cpu 0 is completely busy.
>
> Make sure to try latest Linus tree, as I did yesterday, because
> apparently things are better than a few weeks back.
>
> BTW, even 'perf top' has sometimes problems showing me cycles spent in
> softirq. I need to make sure the cpu processing NIC interrupts also
> spend cycles in some user space program to get meaningful results.
I think that ksoftirqd time is actually accounted to system:
excerpt from irqtime_account_process_tick in kernel/sched/cputime.c
if (this_cpu_ksoftirqd() == p) {
/*
* ksoftirqd time do not get accounted in cpu_softirq_time.
* So, we have to handle it separately here.
* Also, p->stime needs to be updated for ksoftirqd.
*/
__account_system_time(p, cputime, scaled, CPUTIME_SOFTIRQ);
} else if (user_tick) {
