netdev - Re: Quota in __qdisc_run() (was: qdisc: validate skb without holding lock)

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Message-ID: <1412686038.11091.111.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Tue, 07 Oct 2014 05:47:18 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Jesper Dangaard Brouer <brouer@...hat.com>
Cc:	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() (was: qdisc: validate skb without
 holding lock)

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.

Problem with q->bstats.packets is that TSO packets with 45 MSS add 45 to
this counter.

Using a time quota would be better, but : jiffies is too big, and
local_clock() might be too expensive.


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