From owner-freebsd-net@freebsd.org Mon Oct 3 22:02:23 2016 Return-Path: Delivered-To: freebsd-net@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 8EF6CAF347A for ; Mon, 3 Oct 2016 22:02:23 +0000 (UTC) (envelope-from kmacybsd@gmail.com) Received: from mail-vk0-x241.google.com (mail-vk0-x241.google.com [IPv6:2607:f8b0:400c:c05::241]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4B766695; Mon, 3 Oct 2016 22:02:23 +0000 (UTC) (envelope-from kmacybsd@gmail.com) Received: by mail-vk0-x241.google.com with SMTP id b186so1587966vkb.3; Mon, 03 Oct 2016 15:02:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:sender:from:date:message-id:subject:to:cc; bh=M5GMiNtIab/Hiks5x4nu2Pm0aW8WivELAQIpBASTlmo=; b=qS9mSnCNN5abtPP8rOEFWXVA6AvN6bTlfql33vCI3y33q9EM8OhWk5kECPUXF/fUKl 1WKiccQjZIYSOc8bxwxVcJ9fBwqW54pOnNAdnSC+rBg6ebHnvkPBwcAVceBX+76LP5fu XiG7we/ME08wzltqpkXWpTf80V+AmNqmVok6fgSAAA3OvGdaDuYMz3DayKxA0d9MizEE Di6bWelTURZV1wK9oozbhVZzONr/7d4SIe1X319h/cSx3hl4Q9o6r1vpdIyiG05T4VzD vsvX7bILVS91FkiDs8iKVLBUoFOQ4OXuQz7D7P4kx6X92nXLEtVZVFU71zbk7WOfQCIs VtCw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:sender:from:date:message-id:subject :to:cc; bh=M5GMiNtIab/Hiks5x4nu2Pm0aW8WivELAQIpBASTlmo=; b=gZQFA1+9pI0x6LbGzzGx1Xm87EfwRJwLqxKH1/8Zpwb1wr9txX1vyGLmRJkBtv7GHG ye7PZCbNe1mVA8ewFbUSZ1qSsiFKNNvlfMOb5BpfUa4i1Ia7O6hoJ/cWfDMJIdAEl4+w eDjr/kRO5OQKgSnSxf781tyXIFV1ZNmVvyqg9yE3uKAm5xcpVH1tARBByhPQs1OZmg1M 3AH6A2U44o8dlfxhZ1xbRMwwNX5XaGFwreh6+ZBk/ZqRO1hC6u8mD2rLDx5fJWMNJ7bg /miJ5jR9HjbPCebkIundds28f9gWxIqCFgMHFSQVwTXjTLEwjfewJCZYHxWvtRhG3Ebd JIPg== X-Gm-Message-State: AA6/9RmqGjdl+SKPV+ND/23wg6olmQyKOOLlVGMKh/zz0lfcoa+oiXmYAxn9b5362hQR16HBhjCm4VaTs/onPA== X-Received: by 10.31.92.145 with SMTP id q139mr162051vkb.103.1475532142088; Mon, 03 Oct 2016 15:02:22 -0700 (PDT) MIME-Version: 1.0 Sender: kmacybsd@gmail.com Received: by 10.176.69.133 with HTTP; Mon, 3 Oct 2016 15:02:21 -0700 (PDT) From: "K. Macy" Date: Mon, 3 Oct 2016 15:02:21 -0700 X-Google-Sender-Auth: Dl4jCVaO_7b4rNgMMJP6MVCmN7w Message-ID: Subject: TCP_IGNOREIDLE revisited To: "freebsd-net@freebsd.org" Cc: John Baldwin Content-Type: text/plain; charset=UTF-8 X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 03 Oct 2016 22:02:23 -0000 I'm working with a 40GigE mesh where the average RTT is on the order of 10s of microseconds. Consequently, any application idle periods result in poor measured application latency because the congestion window is constantly being reset. I know that this isn't a common use case, but it's clear that there are cases where this is a problem. I think John's response to claims that the internet would melt sum it up best: "The problem with this argument is Linux has already had this as a tunable option for years and the Internet hasn't melted as a result." https://lists.freebsd.org/pipermail/freebsd-net/2013-January/034401.html