Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932929Ab0FQOu4 (ORCPT ); Thu, 17 Jun 2010 10:50:56 -0400 Received: from sh.osrg.net ([192.16.179.4]:50179 "EHLO sh.osrg.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932803Ab0FQOuw (ORCPT ); Thu, 17 Jun 2010 10:50:52 -0400 Date: Thu, 17 Jun 2010 23:50:36 +0900 To: mchan@broadcom.com Cc: JBottomley@novell.com, vapier@gentoo.org, netdev@vger.kernel.org, linux-parisc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: bnx2 fails to compile on parisc because of missing get_dma_ops() From: FUJITA Tomonori In-Reply-To: <20100617230435J.fujita.tomonori@lab.ntt.co.jp> References: <1276780336.2789.6.camel@mulgrave.site> <20100617230435J.fujita.tomonori@lab.ntt.co.jp> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-Id: <20100617234855R.fujita.tomonori@lab.ntt.co.jp> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-3.0 (sh.osrg.net [192.16.179.4]); Thu, 17 Jun 2010 23:50:36 +0900 (JST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2338 Lines: 56 Oops, some typos. On Thu, 17 Jun 2010 23:05:59 +0900 FUJITA Tomonori wrote: > On Thu, 17 Jun 2010 06:30:39 -0700 > "Michael Chan" wrote: > > > James Bottomley wrote: > > > > > On Thu, 2010-06-17 at 05:54 -0700, Michael Chan wrote: > > > > This prefetch improves performance noticeably when the driver is > > > > handling incoming 64-byte packets at a sustained rate. > > > > > > So why not do it unconditionally? The worst that can happen > > > is that you > > > pull in a stale cache line which will get cleaned in the > > > dma_sync, thus > > > slightly degrading performance on incoherent architectures. > > > > The original patch was an unconditional prefetch. There was > > some discussion that it might not be correct if the DMA wasn't > > sync'ed yet on some archs. If the concensus is that it is ok to > > do so, that would be the simplest solution. > > As James said, it just adds useless prefetch on incoherent > architectures. sync_single_for_cpu is called later so we can see the > correct data. One useless prefetch is unlikely to lead performance > drop. > > You might prefer this v2. > > = > From: FUJITA Tomonori > Subject: [PATCH v2] bnx2: fix dma_get_ops compilation breakage > > This removes dma_get_ops() prefetch optimization in bnx2. > > bnx2 uses dma_get_ops() to see if dma_sync_single_for_cpu() is > noop. bnx2 does prefetch if it's noop. > > But dma_get_ops() isn't available on all the architectures (only the > architectures that uses dma_map_ops struct have it). Using > dma_get_ops() in drivers leads to compilation breakage on many > archtectures. s/archtectures/architectures/ > This patch removes dma_get_ops() and changes bnx2 to do prefetch on > all the architectures. This adds useless prefetch on incoherent ~~~~~~~~~~ s/incoherent/non-coherent/ (thanks to Alan) > architectures but this is harmless. It is also unlikely to cause the > performance drop. -- 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/