From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sat, 29 Sep 2001 03:31:52 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sat, 29 Sep 2001 03:31:43 -0400 Received: from sproxy.gmx.de ([213.165.64.20]:27559 "HELO mail.gmx.net") by vger.kernel.org with SMTP id ; Sat, 29 Sep 2001 03:31:31 -0400 Message-ID: <3BB57915.7A702482@gmx.de> Date: Sat, 29 Sep 2001 09:32:37 +0200 From: Bernd Harries Reply-To: bha@gmx.de Organization: BHA Industries X-Mailer: Mozilla 4.75 [en] (X11; U; Linux 2.2.16 i586) X-Accept-Language: en MIME-Version: 1.0 CC: linux-kernel@vger.kernel.org Subject: Re: __get_free_pages(): is the MEM really mine? In-Reply-To: <356.1001580994@www46.gmx.net> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit To: unlisted-recipients:; (no To-header on input)@localhost.localdomain Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org "Eric W. Biederman" wrote: > Ouch. This is where I give you the standard recommendation. If you > do this scatter gatter (so you don't need megs of continuous memory) > you should be much better off, and your driver should be more > reliable. Yep, the firmware on the pixel DSP behind the PLX-9054 bridge wants the base address of a linear 2K * 1K * 2 picture buffer so that it can trigger the one of the 9054's DMA engines to transfer triangles line by line into my memory buffer. If I mmap the PCI space to userland, each read cycle costs 700-900 ns. The DMA engine can use bursts and then a cycle costs only 29.9 ns of PCI bandwidth. > All of the other techniques you have used like mmap should > still apply. > Also if you are exporting this data to user space, before your DMA > complets you want to zero the pages you have allocated, so you don't > have an information leak. The DMA engine in the PLX 9054 can at least do Write-and-Invalidate cycles to the Main RAM. :-) Ciao, -- Bernd Harries bha@gmx.de http://www.freeyellow.com/members/bharries bha@nikocity.de Tel. +49 421 809 7343 priv. | MSB First! harries@stn-atlas.de +49 421 457 3966 offi. | Linux-m68k bernd@linux-m68k.org 8.48'21" E 52.48'52" N | Medusa T40