From owner-freebsd-arch Sun Oct 13 19:14:42 2002 Delivered-To: freebsd-arch@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 71ED637B401 for ; Sun, 13 Oct 2002 19:14:41 -0700 (PDT) Received: from softweyr.com (softweyr.com [65.88.244.127]) by mx1.FreeBSD.org (Postfix) with ESMTP id DA0B343EC2 for ; Sun, 13 Oct 2002 19:14:40 -0700 (PDT) (envelope-from wes@softweyr.com) Received: from nextgig-11.access.nethere.net ([66.63.140.203] helo=softweyr.com) by softweyr.com with esmtp (Exim 3.35 #1) id 180ukD-0006cz-00; Sun, 13 Oct 2002 20:14:09 -0600 Message-ID: <3DAA2B4A.477A6BBE@softweyr.com> Date: Sun, 13 Oct 2002 19:26:18 -0700 From: Wes Peters Organization: Softweyr LLC X-Mailer: Mozilla 4.78 [en] (X11; U; Linux 2.4.2 i386) X-Accept-Language: en MIME-Version: 1.0 To: "M. Warner Losh" Cc: ticso@cicely.de, ticso@cicely8.cicely.de, hch@infradead.org, dillon@apollo.backplane.com, vova@sw.ru, nate@root.org, arch@FreeBSD.org Subject: Re: Database indexes and ram References: <20021012135245.A16453@infradead.org> <20021012.150616.129769790.imp@bsdimp.com> <20021013103538.GG17920@cicely8.cicely.de> <20021013.060648.93373269.imp@bsdimp.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-freebsd-arch@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG "M. Warner Losh" wrote: > > In message: <20021013103538.GG17920@cicely8.cicely.de> > Bernd Walter writes: > : On Sat, Oct 12, 2002 at 03:06:16PM -0600, M. Warner Losh wrote: > : > In message: <20021012135245.A16453@infradead.org> > : > Christoph Hellwig writes: > : > : On Wed, Oct 09, 2002 at 04:57:37PM -0700, Wes Peters wrote: > : > : > Linux solved this problem by refusing to do it. The candidates for DMA > : > : > transfers include skbufs and buffers from the disk buffer pool, both of > : > : > which are allocated from the lowest 4GB of physical ram when using PAE > : > : > mode. > : > : > : > : Umm, Linux _does_ DMA into any memory if the NIC/HBA/whatever supports > : > : it. > : > > : > Unless the card is 64bit, it can't DMA past 4G. > : > : Shouldn't all modern pci chips support two 32bit word addresses. > > I don't think so. There's only 32-bits on the bus for the address on > most pci cards (not the 64-bit pci cards, which are special), so I > don't see how they can go above 4G. Unless I'm being unusually dense > this morning. The PCI spec has a feature for doing two address word transfers so 32-bit cards can DMA/address 64-bit memory regions, but few if any chipsets support it. -- "Where am I, and what am I doing in this handbasket?" Wes Peters Softweyr LLC wes@softweyr.com http://softweyr.com/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message