netdev - Re: [PATCH] sch_htb: ix the deficit overflows

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Date:	Tue, 1 Dec 2009 10:32:26 +0800
From:	Changli Gao <xiaosuo@...il.com>
To:	Jarek Poplawski <jarkao2@...il.com>
Cc:	Jamal Hadi Salim <hadi@...erus.ca>,
	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	Martin Devera <martin.devera@....cz>
Subject: Re: [PATCH] sch_htb: ix the deficit overflows

On Mon, Nov 30, 2009 at 7:10 PM, Jarek Poplawski <jarkao2@...il.com> wrote:
> On Mon, Nov 30, 2009 at 12:26:33PM +0800, Changli Gao wrote:
>
> Users can control this with "r2q" and "quantum", and there is a hint
> on quantum size in the user's guide.

Yes. But I think most of users will ignore it like me.

>
>> And
>> if we use IMQ to shape traffic, the skb will be defragmented by
>> conntrack, and its size will be larger than MTU.
>
> IMQ is a very nice thing, but it's considered broken as well, so it
> can't be the reason for changing HTB.

I find IMQ is used by many network equipments Linux based. Why not fix
and integrate it into official Linux?

> And this patch is very similar, except ->peek()/dequeue(). Additional
> lookups are done instead of dequeuing the first found class, which
> might be quite long in some cases.

If the quantum is set correctly, there isn't difference except of a
comparison. In the other case, I think some additional CPU cycles are
better than overflow.

>
> It's not acceptable to me mainly because the real change done by this
> patch is different than you describe: preventing an overflow might be
> simple. You change the way DRR is implemented here, and even if it's
> right, it should be written explicitly and proved with tests results.
>

This way is used by CBQ.

> Anyway, I think you should rather care for the author's acceptance,
> because the way it's done doesn't look like accidental and has been
> heavily tested btw. (I added Martin to CC.)
>
> Regards,
> Jarek P.
>
> PS: Btw, this newer version of the patch is broken with spaces.
>

Thanks. It is why I ask for posting again.



-- 
Regards，
Changli Gao(xiaosuo@...il.com)
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