netdev - Re: [net-next PATCH 2/3] qdisc: bulk dequeue support for qdiscs with TCQ_F

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Date:	Wed, 3 Sep 2014 12:23:10 +0200
From:	Florian Westphal <fw@...len.de>
To:	Jesper Dangaard Brouer <brouer@...hat.com>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	Florian Westphal <fw@...len.de>,
	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	Daniel Borkmann <dborkman@...hat.com>
Subject: Re: [net-next PATCH 2/3] qdisc: bulk dequeue support for qdiscs with
 TCQ_F_ONETXQUEUE

Jesper Dangaard Brouer <brouer@...hat.com> wrote:
> On Tue, 02 Sep 2014 08:22:42 -0700
> Eric Dumazet <eric.dumazet@...il.com> wrote:
> 
> > On Tue, 2014-09-02 at 16:35 +0200, Jesper Dangaard Brouer wrote:
> > 
> > > This is crazy fast. This measurement is actually "too-high" as
> > > 10Gbit/s wirespeed is 14,880,952 (11049 pps too fast).
> > > 
> > > Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com>
> > > ---
> > 
> > This looks buggy, you forgot about GSO.
> 
> The GSO check is (!skb->next), right(?)

No, you'd want to use skb_is_gso() helper.

> > Also, our idea was to use a byte count limit (aka BQL)
> 
> It makes sense. I will look into using the BQL limits.

Thanks Jesper.

> > If we dequeue 8 64KB packets, this patch adds head of line blocking,
> > which we fought hard.

Just to make sure: Using bql limits would resolve your HOL blocking
concerns, right?
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