netdev - Re: Quota in __qdisc

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Date:	Wed, 08 Oct 2014 10:38:45 -0700
From:	John Fastabend <john.fastabend@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	Jesper Dangaard Brouer <brouer@...hat.com>,
	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	therbert@...gle.com, hannes@...essinduktion.org, fw@...len.de,
	dborkman@...hat.com, jhs@...atatu.com, alexander.duyck@...il.com,
	john.r.fastabend@...el.com, dave.taht@...il.com, toke@...e.dk
Subject: Re: Quota in __qdisc_run()

On 10/07/2014 05:47 AM, Eric Dumazet wrote:
> On Tue, 2014-10-07 at 09:34 +0200, Jesper Dangaard Brouer wrote:
>> On Fri, 03 Oct 2014 16:30:44 -0700 Eric Dumazet <eric.dumazet@...il.com> wrote:
>>
>>> Another problem we need to address is the quota in __qdisc_run()
>>> is no longer meaningfull, if each qdisc_restart() can pump many packets.
>>
>> I fully agree. My earlier "magic" packet limit was covering/pampering
>> over this issue.
>
> Although quota was multiplied by 7 or 8 in worst case ?
>
>>
>>> An idea would be to use the bstats (or cpu_qstats if applicable)
>>
>> Please elaborate some more, as I don't completely follow (feel free to
>> show with a patch ;-)).
>>
>
> I was hoping John could finish the percpu stats before I do that.

What stats are you referring to? I assume the remaining stats in the
xmit path mostly in sch_generic.c? By the way I need to do another
review of the classifier code paths but I believe we could drop the
ingress qdisc lock now (finally)...

Also some clean up in sch_generic.c could help this. Notes for
myself mostly,

	dev_requeue_skb() can be a void its return value is always 0

	the users of handle_dev_cpu_collision and sch_direct_xmit
	don't use the qlen for anything returning any positive
	integer looks like it would work.


Thanks,
John


-- 
John Fastabend         Intel Corporation
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