netdev - Re: [PATCH v3 net-next 1/4] udp: add busylocks in RX path

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Message-ID: <1481227049.4930.132.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Thu, 08 Dec 2016 11:57:29 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Hannes Frederic Sowa <hannes@...essinduktion.org>
Cc:     Eric Dumazet <edumazet@...gle.com>,
        "David S . Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>, Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH v3 net-next 1/4] udp: add busylocks in RX path

On Thu, 2016-12-08 at 20:45 +0100, Hannes Frederic Sowa wrote:
> Hi Eric,
> 

> This patch mostly improves situation for non-connected sockets. Do you
> think it makes sense to acquire the spinlock depending on the sockets
> state? Connected UDP sockets flow in on one CPU anyway?

We could do that, definitely.

However I could not measure any difference with a conditional test here
for connected socket.

Maybe it would show up if we are unlucky and multiple cpus compete on
the same cache line because of the hashed spinlock array.