From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: mail.toke.dk; spf=pass smtp.mailfrom=; dkim=pass header.d=gmx.de header.i=moeller0@gmx.de; arc=none (Message is not ARC signed); dmarc=pass (Used From Domain Record) header.from=gmx.de policy.dmarc=quarantine Received: from mout.gmx.net (mout.gmx.net [212.227.17.20]) by mail.toke.dk (Postfix) with ESMTPS id E176A70F87E for ; Tue, 30 Sep 2025 14:56:52 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmx.de; s=s31663417; t=1759237011; x=1759841811; i=moeller0@gmx.de; bh=IoXsDhhlyRIiUjsoem6Awm3bWWiNYnqh/YwLxaHybkA=; h=X-UI-Sender-Class:Content-Type:Mime-Version:Subject:From: In-Reply-To:Date:Cc:Content-Transfer-Encoding:Message-Id: References:To:cc:content-transfer-encoding:content-type:date:from: message-id:mime-version:reply-to:subject:to; b=mvaSFx+B/vHp7wHuXvH+H2sDNn7L1TaDbadDottE6k8sANHjkdn09a6CzpVWT7Lx vBVu2uRcK1KX9JP/GJY6QxlBa4xew8Xv5gUJCOKx+IbaDMvu3h9qgD9QyjMzE66HI 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3.3.10 Precedence: list Subject: [Cake] Re: help request for cake on a large network List-Id: Cake - FQ_codel the next generation Archived-At: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: Hi David, > On 30. Sep 2025, at 14:37, David Lang wrote: >=20 > Jonathan Morton wrote: >=20 >> On Sunday, 28 September 2025, David Lang wrote: >>> I'm starting to prepare for the next Scale conference and we are = switching from >>> Juniper routers to Linux routers. This gives me the ability to = implement cake. >>>=20 >>> One problem we have is classes that tell everyone 'go download this' = that >>> trigger hundreds of people to hammer the network at the same time = (this is both >>> a wifi and a network bandwidth issue, wifi is being worked on) >>>=20 >>> The network is pretty flat, a couple of subnets each on ipv4 and = ipv6. >>>=20 >>> Any suggestions on how to configure cake for this sort of = environment where >>> there are so many devices? >>=20 >> So far as Cake is concerned, the normal setup should work fine even = under stress conditions. If there are too many simultaneous flows to = achieve full flow isolation, it degrades gracefully to statistical = multiplexing, and you still have the AQM working to keep everything = responsive. Or rather, a thousand AQMs working in parallel... >=20 > what would need to be done to increase resources to allow for full = isolation of more flows? I believe editing net/sched/sch_cake.c and increase the number of = CAKE_QUEUES: #define CAKE_QUEUES (1024) to something larger... however I do not know what a realistic maximum is... and IIRC cake will = search through this repeatedly, 1024 is one full memory page (4k pages) = anything larger will require multiple pages (likely as single contiguous = allocation). I remember dimmly someone ages ago playing with this and = finding that the number can be increased, but not arbitrarily so at = least on your typical somewhat memory-poor router. But that should be = easy to figure out. Mind you, given Toke's reminder on the small number of concurrently = active flows and cake's 8-way associativity, maybe this is not necessary = at all. >=20 >> Of course, this only matters when Cake is set up to be the = bottleneck. If wifi is the bottleneck, you'll want a wifi stack with = integrated fq_codel, which I believe still applies to only some hardware = since it needs to manage the MAC queue which some devices don't expose. = This has the extra smarts needed to adapt gracefully to wifi's foibles, = and might already be enough to convert an effectively nonfunctional wifi = into one that feels, if not fast, then at least reliable. >=20 > I am doing everything I can to eliminate wifi as the bottleneck and = overload our uplink ;-p >=20 > mostly the wifi bottleneck is being eliminated by having lots of = separate APs for people to connect to. >=20 > David Lang > _______________________________________________ > Cake mailing list -- cake@lists.bufferbloat.net > To unsubscribe send an email to cake-leave@lists.bufferbloat.net