From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-x232.google.com (mail-oi0-x232.google.com [IPv6:2607:f8b0:4003:c06::232]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id 2070F3B260; Thu, 5 May 2016 15:41:23 -0400 (EDT) Received: by mail-oi0-x232.google.com with SMTP id v145so114703057oie.0; Thu, 05 May 2016 12:41:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-transfer-encoding; bh=Od+zDgBmEk3VcQyDGlLwUQT9ssCrsF1e+eF8GfgIcJ8=; b=fsEDrPFY8Jn0XNcYwUnCn1jT82naUrX2gMzCHvCQyj2vb/c382l7vykuIOdAFiqsOw 6dHQLcdo3KS5wT/UkZnoYlsCv6b83vT/F1ZxTRFrweeAOwQJEBmX/Wzo8sVF3pfHQjcY 78PWqBb9HhmjKya/o0d1tP0LMFSL9AqlhIyZWJr1cPEHzpJNksmwpdyR8ceDtvTdulbs mrEpCSnAALe/IGr5LTQwrAYQbKjg4P1Swot79Z3nD3n3hYEtHRMncFoXzp2bwBGHZngS s+PN4Fe/VFjXlv0vz0viIGtulZK3xAGz+JVD/bfp8sd6yHREP78xAFE2N5zxSjrSf+1V 6Icw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:date :message-id:subject:from:to:cc:content-transfer-encoding; bh=Od+zDgBmEk3VcQyDGlLwUQT9ssCrsF1e+eF8GfgIcJ8=; b=bsCeCmo17KOFOMLhYdTaVOV/LhWfohnWqS+ZcRiUfKggdRju93Bx1hNpP78Gzr7vIO 3qaBBuoP40W1brJFTXaMnsJuo0b0UpwcygM4IuLgzNbdWJpUjtdQMencEu+l0i3meSY+ BLQePlzEuNjSyBacddTqcJqAATHco+F2feC3kjn60BRIkwS9HVAUhSuzQDkhBD+TC7Gk YO9snJNCGqmb6ykbAUlKF1rQBQO3hoE/KD9usUJg50snAozgkEmrmcSvoWuUuJjKP4pq o013R8PVzni+G2c+MIHjasfZ4Hdbm+lMC6eQrkK1f72Jkhtd7geCDVVSzuIsMd2rWkj9 byHg== X-Gm-Message-State: AOPr4FXzKd2CLBBm9uWZSB3DZfWIqFoss67N7ZXRZR0MfqoltqJMTwkou82NnqWFPaRX3QQcnUHYD+K6CBOQLw== MIME-Version: 1.0 X-Received: by 10.202.185.214 with SMTP id j205mr7120990oif.68.1462477282510; Thu, 05 May 2016 12:41:22 -0700 (PDT) Received: by 10.202.81.76 with HTTP; Thu, 5 May 2016 12:41:22 -0700 (PDT) In-Reply-To: <1462476207.13075.20.camel@edumazet-glaptop3.roam.corp.google.com> References: <1462125592.5535.194.camel@edumazet-glaptop3.roam.corp.google.com> <865DA393-262D-40B6-A9D3-1B978CD5F6C6@gmail.com> <1462128385.5535.200.camel@edumazet-glaptop3.roam.corp.google.com> <1462136140.5535.219.camel@edumazet-glaptop3.roam.corp.google.com> <1462201620.5535.250.camel@edumazet-glaptop3.roam.corp.google.com> <1462205669.5535.254.camel@edumazet-glaptop3.roam.corp.google.com> <1462464776.13075.18.camel@edumazet-glaptop3.roam.corp.google.com> <1462476207.13075.20.camel@edumazet-glaptop3.roam.corp.google.com> Date: Thu, 5 May 2016 12:41:22 -0700 Message-ID: From: Dave Taht To: Eric Dumazet Cc: Roman Yeryomin , Jonathan Morton , make-wifi-fast@lists.bufferbloat.net, "codel@lists.bufferbloat.net" , ath10k Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [Make-wifi-fast] [Codel] fq_codel_drop vs a udp flood X-BeenThere: make-wifi-fast@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 05 May 2016 19:41:23 -0000 On Thu, May 5, 2016 at 12:23 PM, Eric Dumazet wrot= e: > On Thu, 2016-05-05 at 19:25 +0300, Roman Yeryomin wrote: >> On 5 May 2016 at 19:12, Eric Dumazet wrote: >> > On Thu, 2016-05-05 at 17:53 +0300, Roman Yeryomin wrote: >> > >> >> >> >> qdisc fq_codel 0: dev eth0 root refcnt 2 limit 1024p flows 1024 >> >> quantum 1514 target 5.0ms interval 100.0ms ecn >> >> Sent 12306 bytes 128 pkt (dropped 0, overlimits 0 requeues 0) >> >> backlog 0b 0p requeues 0 >> >> maxpacket 0 drop_overlimit 0 new_flow_count 0 ecn_mark 0 >> >> new_flows_len 0 old_flows_len 0 >> > >> > >> > Limit of 1024 packets and 1024 flows is not wise I think. >> > >> > (If all buckets are in use, each bucket has a virtual queue of 1 packe= t, >> > which is almost the same than having no queue at all) >> > >> > I suggest to have at least 8 packets per bucket, to let Codel have a >> > chance to trigger. >> > >> > So you could either reduce number of buckets to 128 (if memory is >> > tight), or increase limit to 8192. >> >> Will try, but what I've posted is default, I didn't change/configure tha= t. > > fq_codel has a default of 10240 packets and 1024 buckets. > > http://lxr.free-electrons.com/source/net/sched/sch_fq_codel.c#L413 > > If someone changed that in the linux variant you use, he probably should > explain the rationale. I guess that would be me. Openwrt has long shipped with the fq_codel default outer queue limit being lower than the default (e.g. 1024). Think: itty bitty 32MB routers. 10240 packets can =3D boom, particuarly while there were 4 fq_codel instances per wifi interface (and people in the habit of creating 2 or more wifi interfaces). back then: I viewed the probability of flooding all 1024 queues as low and thus the queue depth would be sufficient for any given set of flows to do well. (and long ago we gave codel a probability of working on all queues). And did not do enough udp flood testing. :( Totally not the right answer, I know. And the problem is even worse now, with 128MB arm boxes like the armada 385 (linksys 1200ac, turris omnia) using software GRO to be bulking up 64k packets at gigE and trying to ship them to an isp at 5mbit, or over wifi at some rate lower than that. cake switched to byte, rather than packet, accounting, for these reasons, and we're still trying various methods to peel apart superpackets at some load level efficiently. And routers are tending to ship with a lot more memory these days, overall. We are discussing changing the sqm system to dynamically size the packet limit by overall memory limits here, for example: https://github.com/tohojo/sqm-scripts/issues/42 AND: As sorta now implemented in the mac80211 fq_codel code, it's per radio, rather than per interface (or was, when I last thought about it), which is *vastly saner* than four fq_codel instances for each SSID. > > > --=20 Dave T=C3=A4ht Let's go make home routers and wifi faster! With better software! http://blog.cerowrt.org