netdev - Re: [PATCH] net/udp: do not touch skb->peeked unless really needed

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Message-ID: <1481133312.4930.44.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Wed, 07 Dec 2016 09:55:12 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Hannes Frederic Sowa <hannes@...essinduktion.org>
Cc:     David Laight <David.Laight@...LAB.COM>,
        Paolo Abeni <pabeni@...hat.com>,
        David Miller <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Willem de Bruijn <willemb@...gle.com>
Subject: Re: [PATCH] net/udp: do not touch skb->peeked unless really needed

On Wed, 2016-12-07 at 18:37 +0100, Hannes Frederic Sowa wrote:

> I had the same idea while discussing that with Paolo, merely using an
> *atomic_t = kmalloc(sizeof(atomic_t)) out of band of the socket.
> 
> My fear was that those could be aggregated by the slab cache into one
> cache line, causing even more heating on cachelines.

My exact idea was to let up to 4095 (or PAGE_SIZE - 1) increments being
done on the counter before switching to dynamically allocated memory.

( Some packets might be dropped by TCP sockets, not necessarily a sign
of an attack. just some spurious retransmits )