netdev - Re: [RFC] net: remove busylock

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Date:	Thu, 19 May 2016 11:44:10 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org, aduyck@...antis.com
Subject: Re: [RFC] net: remove busylock

On Thu, 2016-05-19 at 11:12 -0700, David Miller wrote:
> From: Eric Dumazet <eric.dumazet@...il.com>
> Date: Thu, 19 May 2016 10:08:36 -0700
> 
> > busylock was added at the time we had expensive ticket spinlocks
> > 
> > (commit 79640a4ca6955e3ebdb7038508fa7a0cd7fa5527 ("net: add additional
> > lock to qdisc to increase throughput")
> > 
> > Now kernel spinlocks are MCS, this busylock things is no longer
> > relevant. It is slowing down things a bit.
>  ...
> > That would be a 8 % increase.
> 
> Presumably only for x86-64 and other platforms that actually are using
> the ticket spinlocks.
> 
> For others it would be a regression.

Ticket spinlocks are actually gone, these are now MCS.

But yes, point taken ;)