From owner-freebsd-net@freebsd.org Fri Nov 6 19:15:50 2015 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 A47A3A2892E; Fri, 6 Nov 2015 19:15:50 +0000 (UTC) (envelope-from adrian.chadd@gmail.com) Received: from mail-io0-x230.google.com (mail-io0-x230.google.com [IPv6:2607:f8b0:4001:c06::230]) (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 6269B1D3B; Fri, 6 Nov 2015 19:15:50 +0000 (UTC) (envelope-from adrian.chadd@gmail.com) Received: by iodd200 with SMTP id d200so131936605iod.0; Fri, 06 Nov 2015 11:15:49 -0800 (PST) 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:content-type; bh=mtkFGAUVN2PuqJ3htuK+pKgdLYxSJCPo8ZqwZyvPZYw=; b=CUBsyTTxDFzxbEOFlNXaUdeMeMJcn/G+PZPTmHni1phlP7W2ucGxyJKowXi/zucc5T a3RHQ6wjqJG3DVrNtAZsILIEkusBVSOliMvZnxO7adPyFxFn6WXqGD26kiwWzE9KRK0W iCO99app/GpDxoi61mIGHXQzzp07Cvk+Jc0jtj9+XeH6EsOIWIyIN01QIcuOHpGC9Sq1 9V9XMnoq9jHjdOnCx/V413dBG4d7A5ko9k6P+Rx8ZoAtfQFIN8SCZGmBRDnj7ODi5tKX BNmjytW1xig2nGIYnuxUbSevKR4zTqsg/ERcd6LRl2HhZr0YLPiZNGqCLab4HuZUItWr LRhA== MIME-Version: 1.0 X-Received: by 10.107.152.2 with SMTP id a2mr16038481ioe.123.1446837349881; Fri, 06 Nov 2015 11:15:49 -0800 (PST) Received: by 10.36.217.196 with HTTP; Fri, 6 Nov 2015 11:15:49 -0800 (PST) In-Reply-To: <1446830585.91534.435.camel@freebsd.org> References: <6545444AE21C2749939E637E56594CEA3C0DCCC4@gsp-ex02.ds.swin.edu.au> <5638B7B5.3030802@selasky.org> <6545444AE21C2749939E637E56594CEA3C0DE7FF@gsp-ex02.ds.swin.edu.au> <563B2703.5080402@selasky.org> <6545444AE21C2749939E637E56594CEA3C0E0BD9@gsp-ex02.ds.swin.edu.au> <563C6864.2090907@selasky.org> <563C786C.1050305@selasky.org> <563CC186.9000807@selasky.org> <563CD533.2000909@selasky.org> <1446828229.91534.417.camel@freebsd.org> <563CDA8F.5010901@selasky.org> <563CDBF9.3090800@selasky.org> <1446830585.91534.435.camel@freebsd.org> Date: Fri, 6 Nov 2015 11:15:49 -0800 Message-ID: Subject: Re: Timing issue with Dummynet on high kernel timer interrupt From: Adrian Chadd To: Ian Lepore Cc: Hans Petter Selasky , Luigi Rizzo , Rasool Al-Saadi , "freebsd-net@freebsd.org" , Alexander Motin , FreeBSD Current Content-Type: text/plain; charset=UTF-8 X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 06 Nov 2015 19:15:50 -0000 Ideally there'd be both behaviours: * You'd specify whether a timer/sleep needs to be exact or can withstand some jitter (which is what linux provides); and * You can communicate to the kernel its aggressiveness for coalescing wakeups. Teaching powerd to flip on/off a sysctl for this isn't that tricky. I remember seeing someone else in #bsdmips having issues figuring out sleep-in-kernel durations and it being exactly this stuff (and it being you, Ian, that figured it out) - so I'd like to at least fix it in -head this time around! Also - I thought the other issue was that precise callouts (versus the default for callouts now which is "fuzzy" unless you specify precision) were still jittering. Is that the case? Thanks, -adrian