netdev - Re: [RFC PATCH] ip: re-introduce fragments cache worker

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Message-ID: <b231fc9a-498d-f59f-0501-3dba62ddaf32@gmail.com>
Date:   Fri, 6 Jul 2018 07:37:36 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Paolo Abeni <pabeni@...hat.com>,
        Eric Dumazet <eric.dumazet@...il.com>, netdev@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Florian Westphal <fw@...len.de>, NeilBrown <neilb@...e.com>
Subject: Re: [RFC PATCH] ip: re-introduce fragments cache worker



On 07/06/2018 06:56 AM, Paolo Abeni wrote:
> With:
> 
> schedule_work_on(smp_processor_id(), #... )
> 
> We can be sure to run exclusively on the cpu handling the RX queue even with the worker.
> 

Make sure to test your patch with 16 RX queues (16 cpus) feeding the defrag unit.

In this (common) mode, then having one cpu trying to purge frags wont be enough.

Really the GC can not cope with DDOS, we tried that in the past (IPv4 route cache)
and failed miserably.