From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-x241.google.com (mail-oi0-x241.google.com [IPv6:2607:f8b0:4003:c06::241]) (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 30C223B25E; Fri, 6 May 2016 14:43:55 -0400 (EDT) Received: by mail-oi0-x241.google.com with SMTP id f63so19378494oig.0; Fri, 06 May 2016 11:43:55 -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; bh=lqQYJuW61ucfEew+d6ar0GEfBOl6UK7oKZqt2ZXbV1g=; b=fLk2bcpXdsEoouHQ03NjcUALZBaH/sKbvhth9PVF+vk+u0w/xETBKmhCecmLovnsxv kJ27p4FyWGyMDMWfcK1fKEwz0le1P5M9cnJrOVMhX9Yze0rUaaa8gRazRtLpyfIDPY9Z gWcz8cJETOB4dwDN17fh4UUa23JoT9yu3xupdwxxjwwsyx6Rz4MCUmbxrLUuFFrcaI0E yegpBAbg14Wdn2M4tWVide4teDuM8QVhXH1fWaONTBYY+EIyE6XZ2JVhSnLGpxi66S4L z5myC3hnetBX6kmvydlE3JeGDV0n3LkkwlpOU94mfOkeW3zh2tQy10bDzEyCtEREJLyf xtrA== 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; bh=lqQYJuW61ucfEew+d6ar0GEfBOl6UK7oKZqt2ZXbV1g=; b=kQEe75baIDoo+GCAwR2F/BmuKBt7PBBKWPD+TxjaF6KEYDP5GMTPiPbbzWQO0CosH+ CfYa8CQ4+hUT0S9+MJFBbAoJCF9SyNfC7AiKj/+1ewuOWdSpb9YXWSSQFsxWM/+fKF53 3SWv0ZkXoqDtaD//q5Yq7wHJNlIp1Y2yPrvm7o02fGc34NdMJMKJLIstcArgesy7Ih/h 2Z7oRSm+4htjOIncKr1H5CRCJ9oxdwDMgOVyREii7qbB/kR7m5oaBE16RFikBGxc+ovZ WBR12r6W+tJJe6rilt32GFqRzAgtduX+siKMPjfxn2sniUQDSlz0YExZ5ol70eja/Rdn FLuA== X-Gm-Message-State: AOPr4FVrtt0luK2SAWRd1F82fkKwbeIaOiTmH9aEmCHfzGCWBVD+SrGru2lnqR+y6IcPOlH4+5pa/mAd/g4vAQ== MIME-Version: 1.0 X-Received: by 10.157.7.86 with SMTP id 80mr9711748ote.168.1462560234411; Fri, 06 May 2016 11:43:54 -0700 (PDT) Received: by 10.202.252.9 with HTTP; Fri, 6 May 2016 11:43:54 -0700 (PDT) In-Reply-To: <20160506144740.210901f5@redhat.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> <20160506114243.4eb4f95e@redhat.com> <20160506144740.210901f5@redhat.com> Date: Fri, 6 May 2016 21:43:54 +0300 Message-ID: From: Roman Yeryomin To: Jesper Dangaard Brouer Cc: Felix Fietkau , Dave Taht , Jonathan Morton , "codel@lists.bufferbloat.net" , ath10k , make-wifi-fast@lists.bufferbloat.net, =?UTF-8?B?UmFmYcWCIE1pxYJlY2tp?= , "netdev@vger.kernel.org" , OpenWrt Development List Content-Type: text/plain; charset=UTF-8 Subject: Re: [Make-wifi-fast] OpenWRT wrong adjustment of fq_codel defaults (Was: [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: Fri, 06 May 2016 18:43:55 -0000 On 6 May 2016 at 15:47, Jesper Dangaard Brouer wrote: > > I've created a OpenWRT ticket[1] on this issue, as it seems that someone[2] > closed Felix'es OpenWRT email account (bad choice! emails bouncing). > Sounds like OpenWRT and the LEDE https://www.lede-project.org/ project > is in some kind of conflict. > > OpenWRT ticket [1] https://dev.openwrt.org/ticket/22349 > > [2] http://thread.gmane.org/gmane.comp.embedded.openwrt.devel/40298/focus=40335 OK, so, after porting the patch to 4.1 openwrt kernel and playing a bit with fq_codel limits I was able to get 420Mbps UDP like this: tc qdisc replace dev wlan0 parent :1 fq_codel flows 16 limit 256 This is certainly better than 30Mbps but still more than two times less than before (900). TCP also improved a little (550 to ~590). Felix, others, do you want to see the ported patch, maybe I did something wrong? Doesn't look like it will save ath10k from performance regression. > > On Fri, 6 May 2016 11:42:43 +0200 > Jesper Dangaard Brouer wrote: > >> Hi Felix, >> >> This is an important fix for OpenWRT, please read! >> >> OpenWRT changed the default fq_codel sch->limit from 10240 to 1024, >> without also adjusting q->flows_cnt. Eric explains below that you must >> also adjust the buckets (q->flows_cnt) for this not to break. (Just >> adjust it to 128) >> >> Problematic OpenWRT commit in question: >> http://git.openwrt.org/?p=openwrt.git;a=patch;h=12cd6578084e >> 12cd6578084e ("kernel: revert fq_codel quantum override to prevent it from causing too much cpu load with higher speed (#21326)") >> >> >> I also highly recommend you cherry-pick this very recent commit: >> net-next: 9d18562a2278 ("fq_codel: add batch ability to fq_codel_drop()") >> https://git.kernel.org/davem/net-next/c/9d18562a227 >> >> This should fix very high CPU usage in-case fq_codel goes into drop mode. >> The problem is that drop mode was considered rare, and implementation >> wise it was chosen to be more expensive (to save cycles on normal mode). >> Unfortunately is it easy to trigger with an UDP flood. Drop mode is >> especially expensive for smaller devices, as it scans a 4K big array, >> thus 64 cache misses for small devices! >> >> The fix is to allow drop-mode to bulk-drop more packets when entering >> drop-mode (default 64 bulk drop). That way we don't suddenly >> experience a significantly higher processing cost per packet, but >> instead can amortize this. >> >> To Eric, should we recommend OpenWRT to adjust default (max) 64 bulk >> drop, given we also recommend bucket size to be 128 ? (thus the amount >> of memory to scan is less, but their CPU is also much smaller). >> >> --Jesper >> >> >> On Thu, 05 May 2016 12:23:27 -0700 Eric Dumazet wrote: >> >> > 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 packet, >> > > > 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 that. >> > >> > 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. > > -- > Best regards, > Jesper Dangaard Brouer > MSc.CS, Principal Kernel Engineer at Red Hat > Author of http://www.iptv-analyzer.org > LinkedIn: http://www.linkedin.com/in/brouer