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 from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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