Messages in this thread | | | Date | Tue, 28 Nov 2006 13:24:51 +0000 (GMT) | From | Mel Gorman <> | Subject | Re: [Patch1/4]: fake numa for x86_64 patch |
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On Mon, 27 Nov 2006, Rohit Seth wrote:
> Hi Mel, > > On Mon, 2006-11-27 at 13:18 +0000, Mel Gorman wrote: >> On Wed, 22 Nov 2006, Rohit Seth wrote: >> >>> This patch provides a IO hole size in a given address range. >>> >> >> Hi, >> >> This patch reintroduces a function that doubles up what >> absent_pages_in_range(start_pfn, end_pfn). I recognise you do this because >> you are interested in hole sizes before add_active_range() is called. > > Right. > >> >> However, what is not clear is why these patches are so specific to x86_64. >> > > Specifically in the fake numa case, we want to make sure that we don't > carve fake nodes that only have IO holes in it. Unlike the real NUMA > case, here we don't have SRAT etc. to know the memory layout beforehand. > > >> It looks possible to do the work of functions like split_nodes_equal() in >> an architecture-independent manner using early_node_map rather than >> dealing with the arch-specific nodes array. That would open the >> possibility of providing fake nodes on more than one architecture in the >> future. > > The functions like splti_nodes_equal etc. can be abstracted out to arch > independent part. I think the only API it needs from arch dependent > part is to find out how much real RAM is present in range without have > to first do add_active_range. >
That is a problem because the ranges must be registered with add_active_range() to work out how much real RAM is present.
> Though as a first step, let us fix the x86_64 (as it doesn't boot when > you have sizeable chunk of IO hole and nodes > 4). >
Ok.
> I'm also not sure if other archs actually want to have this > functionality. >
It's possible that the containers people are interested in the possibility of setting up fake nodes as part of a memory controller.
>> What I think can be done is that you register memory as normal and then >> split up the nodes into fake nodes. This would remove the need for having >> e820_hole_size() reintroduced. > > Are you saying first let the system find out real numa topology and then > build fake numa on top of it? >
Yes, there is nothing stopping you altering the early_node_map[] before free_area_init_node() initialises the node_mem_map. If you do hit a problem, it'll be because x86_64 allocates it's own node_mem_map with CONFIG_FLAT_NODE_MEM_MAP is set. Is that set when setting up fake nodes?
-- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab - 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/
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