netdev - Re: [PATCH 3/3] pkt_sched: restore multiqueue prio scheduler

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Date:	Sat, 23 Aug 2008 15:12:25 +1000
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	alexander.duyck@...il.com (Alexander Duyck)
Cc:	davem@...emloft.net, jarkao2@...il.com, hadi@...erus.ca,
	jeffrey.t.kirsher@...el.com, jeff@...zik.org,
	netdev@...r.kernel.org, alexander.h.duyck@...el.com
Subject: Re: [PATCH 3/3] pkt_sched: restore multiqueue prio scheduler

Alexander Duyck <alexander.duyck@...il.com> wrote:
> 
> That issue led me to the thought of creating a redirect action that
> would take the packet from one qdisc to the correct qdisc for the
> transmit queue.  That setup has two issues.  First, all traffic would
> need to go to one queue by default to avoid a possible deadlock
> condition in the event that two queues try to enqueue packets on one
> another at the same time.  That combined with the fact that one packet

That looks like a problem but it isn't.  When you're overriding
the default queue selection you're breaking CPU affinity.  As such
cache-line bouncing is clearly not a concern or you wouldn't be
doing this (that is, you're doing this for QOS rather than CPU
scalability).  So having everything go through a single qdisc
shouldn't be a problem.

Cheers,
-- 
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Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
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