netdev - Re: [RFC] [PATCH] Avoid enqueuing skb for default qdiscs

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Message-Id: <20090803.205525.156945388.davem@davemloft.net>
Date:	Mon, 03 Aug 2009 20:55:25 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	herbert@...dor.apana.org.au
Cc:	krkumar2@...ibm.com, jarkao2@...il.com, kaber@...sh.net,
	netdev@...r.kernel.org
Subject: Re: [RFC] [PATCH] Avoid enqueuing skb for default qdiscs

From: Herbert Xu <herbert@...dor.apana.org.au>
Date: Tue, 4 Aug 2009 11:49:10 +0800

> On Mon, Aug 03, 2009 at 08:29:35PM -0700, David Miller wrote:
>>
>> Although PFIFO is not work-conserving, isn't it important to retain
>> ordering?  What if higher priority packets are in the queue when we
>> enqueue?  This new bypass will send the wrong packet, won't it?
> 
> The bypass only kicks in if the queue length is zero.

Thanks for explaining, makes sense now.

>> I'm beginning to think, if we want to make the default case go as fast
>> as possible, we should just bypass everything altogether.  The entire
>> qdisc layer, all of it.
> 
> Can you be more specific? AFAICS he's already bypassing the qdisc
> layer when it can be done safely.

Ignore this, it's based upon my missing the part where this
bypass only triggers when the qdisc is empty.
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