netdev - Re: [PATCH take 2] pkt_sched: Fix qdisc_watchdog() vs. dev

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Message-ID: <20080915061922.GA7262@gondor.apana.org.au>
Date:	Sun, 14 Sep 2008 23:19:22 -0700
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Jarek Poplawski <jarkao2@...il.com>
Cc:	Alexander Duyck <alexander.duyck@...il.com>,
	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	kaber@...sh.net
Subject: Re: [PATCH take 2] pkt_sched: Fix qdisc_watchdog() vs.
	dev_deactivate() race

On Mon, Sep 15, 2008 at 06:07:58AM +0000, Jarek Poplawski wrote:
>
> Well, it was only wondering, and probably you are right this is wrong.
> On the other hand, simple_tx_hash() choices are "probabilistic": user
> doesn't care if it goes through tx_queue #1 or #11. And here, in some
> cases, some tx_queues could be always full while other always empty,
> so some dynamic rehashing could be thought of, but I understand it's
> not trivial.

No that would be totally wrong.  One of the important constraints
on a TX hashing mechanism is to preserve packet ordering within
a flow.  If simple_tx_hash started placing the same packet in
different queues then it would do the same thing to flows which
is unacceptable.

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