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Message-ID: <1472734643.5019.9.camel@edumazet-glaptop3.roam.corp.google.com>
Subject: Re: [PATCH] softirq: let ksoftirqd do its job
From: Eric Dumazet <eric.dumazet@gmail.com>
To: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
        David Miller <davem@davemloft.net>, Rik van Riel <riel@redhat.com>,
        Paolo Abeni <pabeni@redhat.com>,
        Hannes Frederic Sowa <hannes@redhat.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        netdev <netdev@vger.kernel.org>, Jonathan Corbet <corbet@lwn.net>
Date: Thu, 01 Sep 2016 05:57:23 -0700
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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.