netdev - Re: [PATCH net-next] sock: avoid dirtying sk

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Message-Id: <20170330.202924.1023519735753552178.davem@davemloft.net>
Date:   Thu, 30 Mar 2017 20:29:24 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     pabeni@...hat.com
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH net-next] sock: avoid dirtying sk_stamp, if possible

From: Paolo Abeni <pabeni@...hat.com>
Date: Thu, 30 Mar 2017 14:03:06 +0200

> sock_recv_ts_and_drops() unconditionally set sk->sk_stamp for
> every packet, even if the SOCK_TIMESTAMP flag is not set in the
> related socket.
> If selinux is enabled, this cause a cache miss for every packet
> since sk->sk_stamp and sk->sk_security share the same cacheline.
> With this change sk_stamp is set only if the SOCK_TIMESTAMP
> flag is set, and is cleared for the first packet, so that the user
> perceived behavior is unchanged.
> 
> This gives up to 5% speed-up under udp-flood with small packets.
> 
> Signed-off-by: Paolo Abeni <pabeni@...hat.com>

Applied, thanks.