From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-1.mimecast.com (us-smtp-2.mimecast.com [207.211.31.81]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id 2234E3B29E for ; Fri, 8 May 2020 11:08:29 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1588950508; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=7H6VfEwMq+1G3yIBkc1pxGsFe64BjsrewGYNqYehMQc=; b=W859hb3sGUiv9Yk72yVQ9SiJReP7SbUo67UboQFqAGqgCHy4NFLy7wrOdiqNDF2ndIMAbK r24NfPd1YqaHMMAzQpPr1Vcl3yFmpxR3QoV12TDzDy99xaWVEWRTEFMXRTl2FSaW1o3V93 2Ku58eO74Hrr4gT+vtgog3StAW0hyYs= Received: from mail-lj1-f198.google.com (mail-lj1-f198.google.com [209.85.208.198]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-151-lBuVMXy9Mr-loTvIxEF17w-1; Fri, 08 May 2020 11:08:26 -0400 X-MC-Unique: lBuVMXy9Mr-loTvIxEF17w-1 Received: by mail-lj1-f198.google.com with SMTP id m4so340497lji.23 for ; Fri, 08 May 2020 08:08:26 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:in-reply-to:references:date :message-id:mime-version; bh=7H6VfEwMq+1G3yIBkc1pxGsFe64BjsrewGYNqYehMQc=; b=rGipnjeKgXPxYitgjXB8sZfhMiBPonJp4k4isj+4er64ZTwGWRX+yPzrMwzOFOQOyE M7r+nTriM6EoC51ob2nds/BNnz6xcFapwvvc5pffHLlIALYhNrFz5bvMU9DP60xMJDUc P5uupXfj+K7DX1BWrGy6csrmpbCNnMoLiYLWBDyozimxI4YJyXUaRNqVhgLnX+yPGKqm hWvx2Rbdhb4Ac0sPEyesSxH+ZZx+zZJuug8UvlfhMHRnLhoPn8VjKU/uEXbnrGjz3X/D VnHeNRHhI+wp19B3+EK75bFaHEqTktBcIVgK4UO/rXRVhKgT0oWeeGR3l6jmFDQRJ66J DlfA== X-Gm-Message-State: AOAM5309zYWKahWFkvqjITSaz28vVS5pjd95ZRdQ8JbGKRMvCBOi7J/r iHQABlRU3fjXAhMBJlLaQeVKE/qYNdOyAA9ZCadZ9GMsQt7N2PUNa7PYKtInkTnb4FteLb8yyq7 psKThukr/1FMf8EzXJwe4fQ== X-Received: by 2002:a2e:8693:: with SMTP id l19mr2012707lji.63.1588950505317; Fri, 08 May 2020 08:08:25 -0700 (PDT) X-Google-Smtp-Source: ABdhPJxuoF/BH65APo1w3UZsjwM8bnUZNo7ktZQwszzLH2AFpQBQVIkvmSIM9q4VDh9dM6innYsU7w== X-Received: by 2002:a2e:8693:: with SMTP id l19mr2012691lji.63.1588950505099; Fri, 08 May 2020 08:08:25 -0700 (PDT) Received: from alrua-x1.borgediget.toke.dk ([45.145.92.2]) by smtp.gmail.com with ESMTPSA id c2sm1406778ljk.97.2020.05.08.08.08.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 08 May 2020 08:08:23 -0700 (PDT) Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id 02E4818151A; Fri, 8 May 2020 17:08:21 +0200 (CEST) From: Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= To: Dave Taht , Avakash bhat Cc: Vybhav Pai , Shrinidhi Varna , Cake List , "Mohit P. Tahiliani" , Deepak K In-Reply-To: References: <87wo5okhbo.fsf@toke.dk> X-Clacks-Overhead: GNU Terry Pratchett Date: Fri, 08 May 2020 17:08:21 +0200 Message-ID: <875zd6h3bu.fsf@toke.dk> MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Subject: Re: [Cake] Query on ACK X-BeenThere: cake@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: Cake - FQ_codel the next generation List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 08 May 2020 15:08:29 -0000 Dave Taht writes: > On Thu, May 7, 2020 at 11:36 PM Avakash bhat wrote: >> >> Ok thanks so much for the clarifications. >> That cleared it up quite a bit. > > I note that there was something really subtle that could have been > done to improve cake's ack handling, and for all I know > it actually happened in the final codebase. > > so, please, go forth and duplicate the existing implementation, and > ignore me, cause looking at this hairy code gives me a > headache. > > anyway, to try and describe what I thought I saw an interaction with > the scheduler back in the day. > > The ack-filter runs, deleting all but one packet from the ack queue, > and delivers that. > the scheduler runs, serves a bunch of other flows, then returns to the > ack queue, which has accumulated a couple more packets, > the ack-filter runs, deleting all but one packet from the ack queue, > and delivers that, but doesn't exhaust its qauntum The ACK filter runs on enqueue, so if a queue has only ACKs in it, it will never accumulate anything in the first place... -Toke