linux-kernel - Re: [RFC PATCH 1/4] softirq: Limit vector to a single iteration on IRQ tail

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Message-Id: <20180119.134727.512994648781037639.davem@davemloft.net>
Date:   Fri, 19 Jan 2018 13:47:27 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     torvalds@...ux-foundation.org
Cc:     frederic@...nel.org, linux-kernel@...r.kernel.org,
        alexander.levin@...izon.com, peterz@...radead.org,
        mchehab@...pensource.com, hannes@...essinduktion.org,
        paulmck@...ux.vnet.ibm.com, wanpeng.li@...mail.com,
        dima@...sta.com, tglx@...utronix.de, akpm@...ux-foundation.org,
        pabeni@...hat.com, rrendec@...sta.com, mingo@...nel.org,
        sgruszka@...hat.com, riel@...hat.com, edumazet@...gle.com
Subject: Re: [RFC PATCH 1/4] softirq: Limit vector to a single iteration on
 IRQ tail

From: Linus Torvalds <torvalds@...ux-foundation.org>
Date: Fri, 19 Jan 2018 10:25:03 -0800

> On Fri, Jan 19, 2018 at 8:16 AM, David Miller <davem@...emloft.net> wrote:
>>
>> So this "get requeued" condition I think will trigger always for
>> networking tunnel decapsulation.
> 
> Hmm. Interesting and a perhaps bit discouraging.
> 
> Will it always be just a _single_ level of indirection, or will double
> tunnels (I assume some people do that, just because the universe is
> out to get us) then result in this perhaps repeating several times?

Every level of tunnel encapsulation will trigger a new softirq.

So if you have an IP tunnel inside of an IP tunnel that will trigger
twice.