Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Mon, 3 Dec 2001 19:21:00 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Mon, 3 Dec 2001 19:16:41 -0500 Received: from deimos.hpl.hp.com ([192.6.19.190]:39402 "EHLO deimos.hpl.hp.com") by vger.kernel.org with ESMTP id ; Mon, 3 Dec 2001 16:48:33 -0500 From: David Mosberger MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <15371.62205.231945.798891@napali.hpl.hp.com> Date: Mon, 3 Dec 2001 13:47:41 -0800 To: Arjan van de Ven Cc: linux-kernel@vger.kernel.org, linux-ia64@linuxia64.org, marcelo@conectiva.com.br, davem@redhat.com Subject: Re: [Linux-ia64] patch to no longer use ia64's software mmu In-Reply-To: <20011203160059.A2022@devserv.devel.redhat.com> In-Reply-To: <20011203160059.A2022@devserv.devel.redhat.com> X-Mailer: VM 6.76 under Emacs 20.4.1 Reply-To: davidm@hpl.hp.com X-URL: http://www.hpl.hp.com/personal/David_Mosberger/ Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Arjan> Hi, The patch below (against 2.4.16) makes the ia64 port no Arjan> longer use the (VERY slow) software IO mmu but makes it use Arjan> the same mechanism the x86 PAE port uses: it lets the higher Arjan> layers take care of the proper bouncing of PCI-unreachable Arjan> memory. The implemenation is pretty simple; instead of having Arjan> a 4Gb GFP_DMA zone and a GFP_KERNEL zone, the Arjan> ia64 port now has a 4Gb GFP_DMA zone and a Arjan> GFP_HIGH zone. Since the ia64 cpu can address all of this Arjan> memory directly, the kmap() and related functions are Arjan> basically nops. Arjan> The result: 100 mbit ethernet performance on a ia64 machine Arjan> with 32Gb of ram increased more than 4x (from 20 mbit to 95 Arjan> mbit).... Arjan> The only downside is that the current kernel will always Arjan> bounce buffer disk IO even if the scsi card is 64 bit PCI Arjan> capable; Jens Axboe's block highmem patch fixes that downside Arjan> nicely though. How soon will Jens' patch make it into the official tree? I think that would be a pre-requisite before switching to a highmem based implementation. Another concern I have is that, fundamentally, I dislike the idea of penalizing all IA-64 platforms due to one chipset that is, shall we say, "lacking" (i.e., doesn't have an I/O TLB). Could someone comment on whether the 870 will have I/O TLB support (private mail is fine, if you don't feel comfortable sending mail to all the lists...). Thanks, --david - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/