From: Jamal Hadi Salim <jhs@mojatatu•com>
To: Jesper Dangaard Brouer <brouer@redhat•com>
Cc: "Tom Herbert" <therbert@google•com>,
"David Miller" <davem@davemloft•net>,
"Linux Netdev List" <netdev@vger•kernel.org>,
"Eric Dumazet" <eric.dumazet@gmail•com>,
"Hannes Frederic Sowa" <hannes@stressinduktion•org>,
"Florian Westphal" <fw@strlen•de>,
"Daniel Borkmann" <dborkman@redhat•com>,
"Alexander Duyck" <alexander.duyck@gmail•com>,
"John Fastabend" <john.r.fastabend@intel•com>,
"Dave Taht" <dave.taht@gmail•com>,
"Toke Høiland-Jørgensen" <toke@toke•dk>
Subject: Re: [net-next PATCH V5] qdisc: bulk dequeue support for qdiscs with TCQ_F_ONETXQUEUE
Date: Wed, 01 Oct 2014 14:55:09 -0400 [thread overview]
Message-ID: <542C4E0D.4050404@mojatatu.com> (raw)
In-Reply-To: <20141001192840.5679a671@redhat.com>
On 10/01/14 13:28, Jesper Dangaard Brouer wrote:
> Thus, code is activated only when q->qlen is >= 1. And I have already
> shown that we see a win with just bulking 2 packets:
If you can get 2 packets, indeed you win. If you can on average get >1
over a long period, you still win.
You have clearly demonstrated you can do that with traffic
generators (udp or in kernel pktgen). I was more worried about the
common use case scenario (handwaved as 1-24 TCP streams).
The key here is: *if you never hit bulking* then the cost is
_per packet_ for sch_direct_xmit bypass.
Question is what is that cost for the common case as defined above?
Can you hit a bulk level >1 on 1-24 TCP streams?
I would be happy if your answer is *yes*. If your answer is no (since
it is hard to achieve) - then how far off is it from before your
patches (since now you have added at minimal a branch check).
I think it is fair for you to quantify that, no?
Feature is still useful for the other cases.
Note:
This is what i referred to as the "no animals were hurt during the
making of these patches" statement. I am sorry again for raining on
the parade.
cheers,
jamal
next prev parent reply other threads:[~2014-10-01 18:55 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-30 8:53 [net-next PATCH V5] qdisc: bulk dequeue support for qdiscs with TCQ_F_ONETXQUEUE Jesper Dangaard Brouer
2014-09-30 11:07 ` Jamal Hadi Salim
2014-09-30 18:20 ` David Miller
2014-10-01 13:17 ` Jamal Hadi Salim
2014-10-01 14:55 ` Tom Herbert
2014-10-01 15:34 ` Jamal Hadi Salim
2014-10-01 17:28 ` Jesper Dangaard Brouer
2014-10-01 18:55 ` Jamal Hadi Salim [this message]
2014-10-01 19:47 ` Jesper Dangaard Brouer
2014-10-01 20:05 ` Jamal Hadi Salim
2014-10-01 20:32 ` Jesper Dangaard Brouer
2014-10-02 5:18 ` Dave Taht
2014-10-02 7:44 ` Jesper Dangaard Brouer
2014-10-02 10:08 ` Toke Høiland-Jørgensen
2014-10-02 13:02 ` Jamal Hadi Salim
2014-10-02 12:53 ` Jamal Hadi Salim
2014-10-01 19:47 ` David Miller
2014-09-30 11:48 ` Eric Dumazet
2014-09-30 12:25 ` Florian Westphal
2014-09-30 12:38 ` Eric Dumazet
2014-09-30 12:41 ` Florian Westphal
2014-09-30 22:07 ` Jesper Dangaard Brouer
2014-09-30 22:15 ` Eric Dumazet
2014-09-30 12:34 ` Eric Dumazet
2014-09-30 12:51 ` [net-next PATCH] dql: add a burst attribute Eric Dumazet
2014-09-30 13:46 ` Florian Westphal
2014-09-30 14:17 ` Eric Dumazet
2014-09-30 14:26 ` Tom Herbert
2014-09-30 14:49 ` Eric Dumazet
2014-09-30 15:05 ` Tom Herbert
2014-09-30 14:31 ` Florian Westphal
2014-09-30 14:55 ` Eric Dumazet
2014-09-30 21:46 ` Jesper Dangaard Brouer
2014-10-01 4:44 ` Tom Herbert
2014-09-30 15:26 ` Florian Westphal
2014-09-30 15:39 ` Dave Taht
2014-09-30 15:41 ` Eric Dumazet
2014-09-30 21:29 ` Jesper Dangaard Brouer
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