From owner-freebsd-current@FreeBSD.ORG Wed May 13 15:34:34 2015 Return-Path: Delivered-To: current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 37440BCE; Wed, 13 May 2015 15:34:34 +0000 (UTC) Received: from mail-ig0-x22a.google.com (mail-ig0-x22a.google.com [IPv6:2607:f8b0:4001:c05::22a]) (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 F1CAE1C03; Wed, 13 May 2015 15:34:33 +0000 (UTC) Received: by igbsb11 with SMTP id sb11so48296844igb.0; Wed, 13 May 2015 08:34:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:sender:in-reply-to:references:date:message-id:subject :from:to:cc:content-type; bh=6oMSv4gLDw6g7UwtrQBJAvrVnckOye68rLywhgLAX5I=; b=xgsQJtELMAW+ZtYNxgpxMoxBF7/xz7MbL6059sgLlGlK6DEVdi+z77NMaEIoKEicC9 B0VXvGChRn/apM774X5SYQ7yiLl7VyxLsfeMfooudweJDuijYkV83wtFrcf+AcyjFbg9 r//VEWBF0e64ubzbeEsb8OCgQyXb1IZKoKYBsKYk8bpeI0P3fYbq1zVF3/MjUIBRjjwo JFKPy1sRc3td2/pjL45Fw4jLuGhuWu2iEvB9h4WNeR12b1AWH2lVCbfKFbiih9gAdL77 926/V9wDZG3YwosNPnrINIq8BWiZO5aFGlVNFaQZSvLhmJ1+Ib3eZIWScDZwHOrMb9kN zLLw== MIME-Version: 1.0 X-Received: by 10.50.57.51 with SMTP id f19mr28762115igq.6.1431531273214; Wed, 13 May 2015 08:34:33 -0700 (PDT) Sender: adrian.chadd@gmail.com Received: by 10.36.38.133 with HTTP; Wed, 13 May 2015 08:34:33 -0700 (PDT) In-Reply-To: <1431528249.1221.15.camel@freebsd.org> References: <20150511230635.GA46991@ivaldir.etoilebsd.net> <20150512032307.GP37063@funkthat.com> <14994.1431412293@critter.freebsd.dk> <20150513080342.GE37063@funkthat.com> <55530CC3.1090204@selasky.org> <1431528249.1221.15.camel@freebsd.org> Date: Wed, 13 May 2015 08:34:33 -0700 X-Google-Sender-Auth: yqLUQBnfxmmTv18E6vUkyXqqGy4 Message-ID: Subject: Re: Increase BUFSIZ to 8192 From: Adrian Chadd To: Ian Lepore Cc: Hans Petter Selasky , David Chisnall , John-Mark Gurney , Poul-Henning Kamp , Baptiste Daroussin , "current@freebsd.org" Content-Type: text/plain; charset=UTF-8 X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 13 May 2015 15:34:34 -0000 [snip] The reason I ask about "why is it faster?" is because for embedded-y things with low RAM we may not want that to happen due to memory constraints. However, we may actually want to do some form of autotuning on some platforms. So, if it's underlying block size, maybe BUFSIZ isn't the thing to tweak, but based on disk io buffer size. If it's filling L1 or L2 cache with useful work, maybe auto-tune it based on that. If it's hiding interrupt latency over USB, then that should be addressed. etc, etc. Please don't take this as bikeshedding, I'd really like to see some "this is why it's faster" analysis rather than just numbers thrown around. -adrian