Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755232AbXF2Uqq (ORCPT ); Fri, 29 Jun 2007 16:46:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753580AbXF2Uqk (ORCPT ); Fri, 29 Jun 2007 16:46:40 -0400 Received: from smtp2.linux-foundation.org ([207.189.120.14]:59651 "EHLO smtp2.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753408AbXF2Uqj (ORCPT ); Fri, 29 Jun 2007 16:46:39 -0400 Date: Fri, 29 Jun 2007 13:45:29 -0700 From: Andrew Morton To: Alan Cox Cc: David Miller , clameter@sgi.com, hugh@veritas.com, James.Bottomley@steeleye.com, rmk+lkml@arm.linux.org.uk, linux-kernel@vger.kernel.org Subject: Re: [PATCH] Containment measures for slab objects on scatter gather lists Message-Id: <20070629134529.3e12a131.akpm@linux-foundation.org> In-Reply-To: <20070629131657.5ecc3baa@the-village.bc.nu> References: <20070628.220606.112621271.davem@davemloft.net> <20070628222424.4cbae90c.akpm@linux-foundation.org> <20070628.223734.21928089.davem@davemloft.net> <20070628224519.1a3319c3.akpm@linux-foundation.org> <20070629131657.5ecc3baa@the-village.bc.nu> X-Mailer: Sylpheed version 2.2.7 (GTK+ 2.8.6; i686-pc-linux-gnu) 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 Content-Length: 1097 Lines: 24 On Fri, 29 Jun 2007 13:16:57 +0100 Alan Cox wrote: > > If those operations involve modifying that slab page's pageframe then what > > stops concurrent dma'ers from stomping on each other's changes? As in: > > why aren't we already buggy? > > Or DMA operations falling out with CPU operations in the same memory > area. Not all platforms have hardware consistency and some will blat the > entire page out of cache. Is that just a performance problem, or can data be lost here? It depends on the meaning of "blat": writeback? invalidate? More details, please. I'm dyin here and nobody will talk to me. If the kernel is already doing these things, why aren't we already buggy? Is it because we don't actually modify the pageframes of these dma-to-from-kmalloced pages? But we were thinking of doing so in the future? - 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/