From owner-freebsd-arch@FreeBSD.ORG Wed Dec 26 01:19:19 2012 Return-Path: Delivered-To: arch@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 6D440D0B for ; Wed, 26 Dec 2012 01:19:19 +0000 (UTC) (envelope-from imp@bsdimp.com) Received: from mail-ie0-f179.google.com (mail-ie0-f179.google.com [209.85.223.179]) by mx1.freebsd.org (Postfix) with ESMTP id 236628FC0A for ; Wed, 26 Dec 2012 01:19:18 +0000 (UTC) Received: by mail-ie0-f179.google.com with SMTP id k14so10021913iea.24 for ; Tue, 25 Dec 2012 17:19:18 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=x-received:sender:subject:mime-version:content-type:from :in-reply-to:date:cc:content-transfer-encoding:message-id:references :to:x-mailer:x-gm-message-state; bh=IEo3d6P6SgB/ZDl4fjhC1uCFgaTEsBLnVKC41Qv46TY=; b=cRTXtiHh6WATvNinFCyhsIKdUTitOD11UAUGdZD99E9nw+Tx6rZJzYDBnQQu8rZwyG n5ThCz9dgxFDWK1qYZL6qBHNJoIUxD1Oucs5DG4vdWx+nJW7tps3pTIS9qidhzBfnG+C 7shWghK7RVeklNlKu+aPOPyJuSMhT749BZsMU8/HLPYQw0r+CFvdH2HSIhdKS2/nACwp Cji3ajQxplz9HUsBLcARM4zSE6JZWonmVQhUcFA8/itJtjlvjcrbTN4lHJ3RKc1Eeuow bNOEiI7fd7iccUT/sJ+YMBjd4Vsh8qoPILmWwanzvaURyMXxP1pF0zx5F7PZ01WqjveU +NYg== X-Received: by 10.50.196.138 with SMTP id im10mr17856423igc.83.1356484758053; Tue, 25 Dec 2012 17:19:18 -0800 (PST) Received: from 53.imp.bsdimp.com (50-78-194-198-static.hfc.comcastbusiness.net. [50.78.194.198]) by mx.google.com with ESMTPS id fv6sm25712024igc.17.2012.12.25.17.19.16 (version=TLSv1/SSLv3 cipher=OTHER); Tue, 25 Dec 2012 17:19:17 -0800 (PST) Sender: Warner Losh Subject: Re: Unmapped I/O Mime-Version: 1.0 (Apple Message framework v1085) Content-Type: text/plain; charset=us-ascii From: Warner Losh In-Reply-To: <20121225204854.GE82219@kib.kiev.ua> Date: Tue, 25 Dec 2012 18:19:15 -0700 Content-Transfer-Encoding: quoted-printable Message-Id: <58BA8294-A610-4474-A8B4-9AF69AD44779@bsdimp.com> References: <20121219135451.GU71906@kib.kiev.ua> <50D22EA6.1040501@rice.edu> <20121225204854.GE82219@kib.kiev.ua> To: Konstantin Belousov X-Mailer: Apple Mail (2.1085) X-Gm-Message-State: ALoCoQkCoZ4yp7A1l2aMtSyO2D2p+lUuCkZd317fShEGX23zpTPW1Zk6n+gE8RG0IQE6WLaxxNRH Cc: alc@freebsd.org, arch@freebsd.org, Robert Watson , Alan Cox X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 26 Dec 2012 01:19:19 -0000 On Dec 25, 2012, at 1:48 PM, Konstantin Belousov wrote: > On Tue, Dec 25, 2012 at 08:42:27PM +0000, Robert Watson wrote: >> On Wed, 19 Dec 2012, Alan Cox wrote: >>=20 >>>> Are the machines that don't have a direct map performance critical? = My=20 >>>> expectation is that they are legacy or embedded. This seems like a = great=20 >>>> project to do when the rest of the pieces are stable and fast. = Until then=20 >>>> they could just use something like pbufs? >>>=20 >>> I think the answer to your first question depends entirely on who = you are.=20 >>> :-) Also, at the low-end of the server space, there are many people = trying=20 >>> to promote arm-based systems. While FreeBSD may never run on your = arm-based=20 >>> phone, I think that ceding the arm-based server market to others = will be a=20 >>> strategic mistake. >>>=20 >>> Alan >>>=20 >>> P.S. I think we're moving the discussion to far away from kib's = original, so=20 >>> I suggest changing the subject line on any follow ups. >>=20 >> Despite moving the discussion a little further away: MIPS-based >> systems, a direct mapped map segment (e.g., kseg, xkphys, etc) is = part >> of the underlying design and doesn't rely on any TLB entries at all. >> We run much of the kernel from direct map regions to avoid causing = TLB >> pressure. > Yes, as it was noted already, 32bit mips kseg is not much usable on > the mips systems with more than 1GB of RAM. But Alan' another patch, > with, I believe, small modification, could provide the gain there too. Most mips move to 64-bit when they have more than 512MB or 1GB because = the direct map is just too handy... Warner=