From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-x229.google.com (mail-wm0-x229.google.com [IPv6:2a00:1450:400c:c09::229]) (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 769303B2A0 for ; Tue, 19 Jul 2016 09:10:50 -0400 (EDT) Received: by mail-wm0-x229.google.com with SMTP id o80so25861278wme.1 for ; Tue, 19 Jul 2016 06:10:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=tieto.com; s=google; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=HZ94bh4dxxg7T9IehvuxQQPOXkt5282DhWbaaLVySRw=; b=C+lF7eRm98LM/uHDvsDkNcwHj82Ab6qEM6qbaM02WByRWtvkasuYfrC6B6Bj7LGdEq tPV1DOI/OH+HFYFoqEwRXjnQFtnwh6Mc5dNgRm/Ww0h05WiOybWKkI/fGs63w+Kqw4za uexAoDu638InbKn0g0h0GKA82EGJdPnzzvW0s= 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:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=HZ94bh4dxxg7T9IehvuxQQPOXkt5282DhWbaaLVySRw=; b=nJ/WzLQgiCgRbNQE+O1aZSdJmkCsQ4goTI55D2SZip3BpdHywpxLNuMEDM/UAfP5vm vPq8ezYasUuV2i0qy0GDo+lK0iD1J0IK4S7SB3v3IZerSBSmb52pJmHvNDWiASD91nV1 Ptd1TTO9SXKjbLezEpJ1NhKeLn4PNjg+ZXKJQwLXUqIlWfgRQdtdiQJFI3st5xOYLgvj wbAVv3wP92abFWPynIkIt/TitXnok7m4ohklI/MMWYG7PKr+cUEj2z5YRexNkJdB6mzH PbQMMbVwB4BEllFnWSeD5UOGlNwiV2zhdEltm1Be/q3pVDnL8dVLqWCR6MXI8/ekIIjA NkXA== X-Gm-Message-State: ALyK8tKzx78UycCCNjjUf8AR7zNcbIRkhYw+EqCwB+GyWViU/8EM33IKXkePM3otv4LWfliBB6ng9Vvyn4t5DzQ04uTzbJj/BAgnklbO7oGcCoYPFb1bRcKBXI1SmwR4yKY+qSDltmZnYLcXH8I7BxUef+br1QzCw5pSuQ== X-Received: by 10.28.60.136 with SMTP id j130mr4469040wma.93.1468933849519; Tue, 19 Jul 2016 06:10:49 -0700 (PDT) MIME-Version: 1.0 Received: by 10.194.172.4 with HTTP; Tue, 19 Jul 2016 06:10:48 -0700 (PDT) In-Reply-To: References: <11fa6d16-21e2-2169-8d18-940f6dc11dca@nbd.name> <097af8e4-5393-8e1b-1748-36233e605867@nbd.name> From: Michal Kazior Date: Tue, 19 Jul 2016 15:10:48 +0200 Message-ID: To: Dave Taht Cc: Felix Fietkau , make-wifi-fast@lists.bufferbloat.net, linux-wireless , =?UTF-8?B?VG9rZSBIw7hpbGFuZC1Kw7hyZ2Vuc2Vu?= Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-DomainID: tieto.com Subject: Re: [Make-wifi-fast] TCP performance regression in mac80211 triggered by the fq code 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: Tue, 19 Jul 2016 13:10:50 -0000 On 12 July 2016 at 16:02, Dave Taht wrote: [...] >>> tcp_limit_output_bytes is? >> 262144 > > I keep hoping to be able to reduce this to something saner like 4096 > one day. It got bumped to 64k based on bad wifi performance once, and > then to it's current size to make the Xen folk happier. Not sure if it's possible. You do need this to be at least as big as a single A-MPDU can get. In extreme 11ac cases it can be pretty big. I recall a discussion from a long time ago and the tcp limit output logic was/is coupled with the assumption that tx-completions always come max 1ms after tx submission. This is rather tricky to *guarantee* on wifi, especially with firmware blobs, big aggregates, lots of stations and retries. Micha=C5=82