netdev - Re: [PATCH v4 net-next 1/1] net_sched: Introduce skbmod action

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Message-ID: <1473719192.18970.84.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Mon, 12 Sep 2016 15:26:32 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Jamal Hadi Salim <jhs@...atatu.com>
Cc:     davem@...emloft.net, netdev@...r.kernel.org,
        xiyou.wangcong@...il.com, daniel@...earbox.net,
        john.r.fastabend@...el.com
Subject: Re: [PATCH v4 net-next 1/1] net_sched: Introduce skbmod action

On Mon, 2016-09-12 at 18:14 -0400, Jamal Hadi Salim wrote:

> I noticed some very weird issues when I took that out.
> Running sufficiently large amount of traffic (ping -f is sufficient)
> I saw that when i did a dump it took anywhere between 6-15 seconds.
> With the read_lock in place response was immediate.
> I can go back and run things to verify - but it was very odd.

This was on uni processor ?

Looks like typical starvation caused by aggressive softirq.

Anyway, I suspect your kernel build has rcu_read_lock() and
rcu_read_unlock() as NOP ;)