From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 12 Sep 2006 10:53:56 -0700 (PDT) From: Christoph Lameter Subject: Re: [PATCH 0/8] Optional ZONE_DMA V1 In-Reply-To: <4506F2B9.5020600@google.com> Message-ID: References: <20060911222729.4849.69497.sendpatchset@schroedinger.engr.sgi.com> <20060912133457.GC10689@sgi.com> <4506F2B9.5020600@google.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Martin Bligh Cc: Jack Steiner , Linux Memory Management , Nick Piggin , Christoph Hellwig , linux-ia64@vger.kernel.org, Marcelo Tosatti , Arjan van de Ven , KAMEZAWA Hiroyuki , Andi Kleen List-ID: On Tue, 12 Sep 2006, Martin Bligh wrote: > > This is wrong. All memory should be in ZONE_NORMAL since we have no DMA > > restrictions on Altix. > > PPC64 works the same way, I believe. All memory is DMA'able, therefore > it all fits in ZONE_DMA. ZONE_DMA is for broken/limited DMA controllers not for DMA controllers that can reach all of memory. > The real problem is that there's no consistent definition of what the > zones actually mean. ZONE_DMA Special memory area for DMA controllers that can only do dma to a restricted memory area. ZONE_DMA32 Second special memory area for DMA controllers that can only do dma to a restricted memory area that is different from ZONE_DMA ZONE_NORMAL Regular memory ZONE_HIGHEM Memory requires being mapped into kernel address space. > 1. Is it DMA'able (this is stupid, as it doesn't say 'for what device' That is *not* what ZONE_DMA means. We have always supported DMA to regular memory. > What is really needed is to pass a physical address limit from the > caller, together with a flag that says whether the memory needs to be > mapped into the permanent kernel address space or not. The allocator > then finds the set of zones that will fulfill this criteria. > But I suspect this level of change will cause too many people to squeak > loudly. Actually we could do this with the proposed change of passing an allocation_control struct instead of gfpflags to the allocator functions. See the discussion on linux-mm. -- 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