Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Thu, 13 Jun 2002 04:51:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Thu, 13 Jun 2002 04:51:31 -0400 Received: from pizda.ninka.net ([216.101.162.242]:4059 "EHLO pizda.ninka.net") by vger.kernel.org with ESMTP id ; Thu, 13 Jun 2002 04:51:29 -0400 Date: Thu, 13 Jun 2002 01:47:00 -0700 (PDT) Message-Id: <20020613.014700.26430433.davem@redhat.com> To: saw@saw.sw.com.sg Cc: fxzhang@ict.ac.cn, linux-mips@oss.sgi.com, linux-kernel@vger.kernel.org, netdev@oss.sgi.com, jgarzik@mandrakesoft.com Subject: Re: NAPI for eepro100 From: "David S. Miller" In-Reply-To: <20020613125753.A23693@castle.nmd.msu.ru> X-Mailer: Mew version 2.1 on Emacs 21.1 / Mule 5.0 (SAKAKI) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org From: Andrey Savochkin Date: Thu, 13 Jun 2002 12:57:53 +0400 On Wed, Jun 12, 2002 at 04:05:32PM -0700, David S. Miller wrote: > No, it's worse than that. > > See how non-consistent memory is used by the eepro100 driver > for descriptor bits? The skb->tail bits? > > That is very problematic. What's the problem? If it isn't allowed to do, then what is the meaning of PCI_DMA_BIDIRECTIONAL mappings? It's slow. Not wrong, just inefficient. Descriptors were meant to be done using consistent mappings, not "pci_map_*()"'d memory. The latter is meant to be used for long linear DMA transfers to/from the device. It is not meant for things the cpu pokes small bits of data in and out of, that is what consistent DMA memory is for. - 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/