From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from westrelay02.boulder.ibm.com (westrelay02.boulder.ibm.com [9.17.195.11]) by e36.co.us.ibm.com (8.12.11/8.12.11) with ESMTP id jA1FXOkE021960 for ; Tue, 1 Nov 2005 10:33:24 -0500 Received: from d03av04.boulder.ibm.com (d03av04.boulder.ibm.com [9.17.195.170]) by westrelay02.boulder.ibm.com (8.12.10/NCO/VERS6.7) with ESMTP id jA1FXOXg407508 for ; Tue, 1 Nov 2005 08:33:24 -0700 Received: from d03av04.boulder.ibm.com (loopback [127.0.0.1]) by d03av04.boulder.ibm.com (8.12.11/8.13.3) with ESMTP id jA1FXON0030134 for ; Tue, 1 Nov 2005 08:33:24 -0700 Subject: Re: [Lhms-devel] [PATCH 0/7] Fragmentation Avoidance V19 From: Dave Hansen In-Reply-To: <45430000.1130858744@[10.10.2.4]> References: <20051030183354.22266.42795.sendpatchset@skynet.csn.ul.ie> <20051031055725.GA3820@w-mikek2.ibm.com><4365BBC4.2090906@yahoo.com.au> <20051030235440.6938a0e9.akpm@osdl.org> <27700000.1130769270@[10.10.2.4]> <4366A8D1.7020507@yahoo.com.au> <4366C559.5090504@yahoo.com.au> <45430000.1130858744@[10.10.2.4]> Content-Type: text/plain Date: Tue, 01 Nov 2005 16:33:13 +0100 Message-Id: <1130859193.14475.104.camel@localhost> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: "Martin J. Bligh" Cc: Nick Piggin , Mel Gorman , Andrew Morton , kravetz@us.ibm.com, linux-mm , Linux Kernel Mailing List , lhms , Ingo Molnar List-ID: On Tue, 2005-11-01 at 07:25 -0800, Martin J. Bligh wrote: > > I really don't think we *want* to say we support higher order allocations > > absolutely robustly, nor do we want people using them if possible. Because > > we don't. Even with your patches. > > > > Ingo also brought up this point at Ottawa. > > Some of the driver issues can be fixed by scatter-gather DMA *if* the > h/w supports it. But what exactly do you propose to do about kernel > stacks, etc? By the time you've fixed all the individual usages of it, > frankly, it would be easier to provide a generic mechanism to fix the > problem ... That generic mechanism is the kernel virtual remapping. However, it has a runtime performance cost, which is increased TLB footprint inside the kernel, and a more costly implementation of __pa() and __va(). I'll admit, I'm biased toward partial solutions without runtime cost before we start incurring constant cost across the entire kernel, especially when those partial solutions have other potential in-kernel users. -- Dave -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org