From: Eric Dumazet <eric.dumazet@gmail.com>
To: Jonathan Morton <chromatix99@gmail.com>
Cc: Dave Taht <dave.taht@gmail.com>,
make-wifi-fast@lists.bufferbloat.net,
"codel@lists.bufferbloat.net" <codel@lists.bufferbloat.net>,
ath10k <ath10k@lists.infradead.org>
Subject: Re: [Codel] fq_codel_drop vs a udp flood
Date: Sun, 01 May 2016 11:46:25 -0700 [thread overview]
Message-ID: <1462128385.5535.200.camel@edumazet-glaptop3.roam.corp.google.com> (raw)
In-Reply-To: <865DA393-262D-40B6-A9D3-1B978CD5F6C6@gmail.com>
On Sun, 2016-05-01 at 21:20 +0300, Jonathan Morton wrote:
> > On 1 May, 2016, at 20:59, Eric Dumazet <eric.dumazet@gmail.com> wrote:
> >
> > fq_codel_drop() could drop _all_ packets of the fat flow, instead of a
> > single one.
>
> Unfortunately, that could have bad consequences if the “fat flow”
> happens to be a TCP in slow-start on a long-RTT path. Such a flow is
> responsive, but on an order-magnitude longer timescale than may have
> been configured as optimum.
Are you trying to reinvent Hystart ? ;)
>
> The real problem is that fq_codel_drop() performs the same (excessive)
> amount of work to cope with a single unresponsive flow as it would for
> a true DDoS. Optimising the search function is sufficient.
Optimizing the search function is not possible, unless you slow down the
fast path. This was my design choice.
Just drop half backlog packets instead of 1, (maybe add a cap of 64
packets to avoid too big burts of kfree_skb() which might add cpu
spikes) and problem is gone.
TCP in slow start wont be hurt at all. A fat TCP flow is still fat.
Only bad CC could possibly be hurt.
next prev parent reply other threads:[~2016-05-01 18:46 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-01 3:41 Dave Taht
2016-05-01 4:46 ` [Codel] [Make-wifi-fast] " Jonathan Morton
2016-05-01 5:08 ` [Codel] " Ben Greear
2016-05-01 5:23 ` Dave Taht
2016-05-01 14:47 ` [Codel] [Make-wifi-fast] " dpreed
[not found] ` <CAJq5cE2woA3yb6i_7NLPpxjzvhsVk5uL8BnSTAY7Lp-M0KiPNg@mail.gmail.com>
[not found] ` <CAJq5cE2K0yrz6ALAoKWu23RSJZX9Y_P7Mqcy9ba8e-L3AVhOaA@mail.gmail.com>
2016-05-01 15:51 ` Jonathan Morton
[not found] ` <CACiydb+nNEWfO8XS63MnrW0LazORAGX+L+fF1xZ2_2sCLeRAsg@mail.gmail.com>
2016-05-02 18:40 ` Dave Taht
2016-05-02 20:17 ` Isaac Konikoff
2016-05-05 13:55 ` Roman Yeryomin
2016-05-05 14:55 ` Roman Yeryomin
2016-05-02 19:47 ` David Lang
2016-05-01 17:59 ` [Codel] " Eric Dumazet
2016-05-01 18:20 ` Jonathan Morton
2016-05-01 18:46 ` Eric Dumazet [this message]
2016-05-01 19:55 ` Eric Dumazet
2016-05-02 7:47 ` Jesper Dangaard Brouer
2016-05-01 20:35 ` Jonathan Morton
2016-05-01 20:55 ` Eric Dumazet
[not found] ` <CACiydbKUu11=zWitkDha0ddgk1-G_Z4-e1+=9ky776VktF5HHg@mail.gmail.com>
2016-05-02 15:07 ` Eric Dumazet
[not found] ` <CACiydbKeKUENncrc-NmYRcku-DGVeGqqzYMqsCqKdxPsR7yUOQ@mail.gmail.com>
2016-05-02 16:14 ` Eric Dumazet
2016-05-02 17:08 ` Dave Taht
2016-05-02 17:44 ` Eric Dumazet
2016-05-05 14:32 ` Roman Yeryomin
2016-05-05 14:53 ` Roman Yeryomin
2016-05-05 15:32 ` Dave Taht
2016-05-05 16:07 ` Roman Yeryomin
2016-05-05 16:59 ` Jonathan Morton
2016-05-05 17:39 ` Roman Yeryomin
2016-05-05 18:16 ` Dave Taht
2016-05-05 18:33 ` Dave Taht
2016-05-05 16:12 ` Eric Dumazet
2016-05-05 16:25 ` Roman Yeryomin
2016-05-05 16:42 ` Roman Yeryomin
2016-05-06 10:55 ` Roman Yeryomin
2016-05-05 19:23 ` Eric Dumazet
2016-05-05 19:41 ` Dave Taht
2016-05-06 8:41 ` moeller0
2016-05-06 11:33 ` Jesper Dangaard Brouer
2016-05-06 11:46 ` moeller0
2016-05-06 13:25 ` Eric Dumazet
2016-05-06 15:25 ` moeller0
2016-05-06 15:58 ` Eric Dumazet
2016-05-06 16:30 ` moeller0
2016-05-06 9:42 ` [Codel] OpenWRT wrong adjustment of fq_codel defaults (Was: fq_codel_drop vs a udp flood) Jesper Dangaard Brouer
2016-05-06 12:47 ` Jesper Dangaard Brouer
2016-05-06 18:43 ` Roman Yeryomin
2016-05-06 18:56 ` Roman Yeryomin
2016-05-06 19:43 ` Dave Taht
2016-05-15 22:34 ` Roman Yeryomin
2016-05-15 23:07 ` Eric Dumazet
2016-05-15 23:27 ` Roman Yeryomin
2016-05-16 8:12 ` [Codel] [Make-wifi-fast] " David Lang
2016-05-16 8:26 ` Roman Yeryomin
2016-05-16 8:46 ` David Lang
2016-05-16 10:34 ` [Codel] [OpenWrt-Devel] " Sebastian Moeller
2016-05-16 8:14 ` [Codel] " Roman Yeryomin
2016-05-16 14:23 ` [Codel] [Make-wifi-fast] " Eric Dumazet
2016-05-16 16:04 ` [Codel] " Dave Taht
2016-05-16 19:46 ` Roman Yeryomin
[not found] ` <572DBC21.10209@darbyshire-bryant.me.uk>
2016-05-15 22:47 ` Roman Yeryomin
2016-05-03 2:26 ` [Codel] fq_codel_drop vs a udp flood Dave Taht
2016-05-03 5:21 ` Dave Taht
2016-05-03 12:39 ` Agarwal, Anil
2016-05-03 12:50 ` Agarwal, Anil
2016-05-03 13:35 ` Eric Dumazet
2016-05-03 15:37 ` Agarwal, Anil
2016-05-03 17:37 ` Dave Taht
2016-05-03 17:54 ` Eric Dumazet
2016-05-03 18:11 ` Dave Taht
2016-05-01 18:26 ` Dave Taht
2016-05-01 22:30 ` Eric Dumazet
[not found] ` <CACiydbL0K2fQT4EXm4LjDaxDLC+AVj9szTpyHq2iUwuPVNNz+g@mail.gmail.com>
2016-05-02 15:04 ` Eric Dumazet
[not found] ` <CACiydbJStMOr0HKpw68zxDPgQRdwjR88aDis9fv12umzKAvWqw@mail.gmail.com>
2016-05-02 15:01 ` [Codel] [Make-wifi-fast] " Eric Dumazet
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