From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: [RFC PATCH] net: add additional lock to qdisc to increase
 enqueue/dequeue fairness
Date: Fri, 21 May 2010 19:40:43 +0200
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Cc: David Miller <davem@davemloft.net>, alexander.h.duyck@intel.com,
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Le vendredi 21 mai 2010 =C3=A0 18:44 +0200, Eric Dumazet a =C3=A9crit :

> We could use cmpxchg() and manipulate several bits at once in fast pa=
th.
> ( __QDISC_STATE_RUNNING, __QDISC_STATE_LOCKED ... ) but making the cr=
owd
> of cpus spin on the same bits/cacheline than dequeue worker would
> definitely slowdown the worker.
>=20
>=20

Maybe I am missing something, but __QDISC_STATE_RUNNING is always
manipulated with the lock held...

We might avoid two atomic ops when changing this state (if moved to a
separate container) in fast path (when a cpu sends only one packet and
returns)