netdev - Re: 100% CPU load when generating traffic to destination network that nexthop is not reachable

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Message-ID: <1502816253.4936.85.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Tue, 15 Aug 2017 09:57:33 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Paweł Staszewski <pstaszewski@...are.pl>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: 100% CPU load when generating traffic to destination network
 that nexthop is not reachable

On Tue, 2017-08-15 at 18:30 +0200, Paweł Staszewski wrote:
> Hi
> 
> 
> Doing some tests i discovered that when traffic is send by pktgen to 
> forwarding host where nexthop for destination network on forwarding 
> router is not reachable i have 100% cpu on all cores and perf top show 
> mostly:
> 
>      77.19%  [kernel]            [k] queued_spin_lock_slowpath
>      10.20%  [kernel]            [k] acpi_processor_ffh_cstate_enter
>       1.41%  [kernel]            [k] queued_write_lock_slowpath
> 

To the rescue (for us to help)

perf record -a -g sleep 10

perf report --stdio