Messages in this thread |  | | Date | Thu, 13 Feb 2014 14:41:04 -0800 (PST) | From | David Rientjes <> | Subject | Re: [RFC PATCH V5] mm readahead: Fix readahead fail for no local memory and limit readahead pages |
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On Thu, 13 Feb 2014, Raghavendra K T wrote:
> Thanks David, unfortunately even after applying that patch, I do not see > the improvement. > > Interestingly numa_mem_id() seem to still return the value of a > memoryless node. > May be per cpu _numa_mem_ values are not set properly. Need to dig out .... >
I believe ppc will be relying on __build_all_zonelists() to set numa_mem_id() to be the proper node, and that relies on the ordering of the zonelist built for the memoryless node. It would be very strange if local_memory_node() is returning a memoryless node because it is the first zone for node_zonelist(GFP_KERNEL) (why would a memoryless node be on the zonelist at all?).
I think the real problem is that build_all_zonelists() is only called at init when the boot cpu is online so it's only setting numa_mem_id() properly for the boot cpu. Does it return a node with memory if you toggle /proc/sys/vm/numa_zonelist_order? Do
echo node > /proc/sys/vm/numa_zonelist_order echo zone > /proc/sys/vm/numa_zonelist_order echo default > /proc/sys/vm/numa_zonelist_order
and check if it returns the proper value at either point. This will force build_all_zonelists() and numa_mem_id() to point to the proper node since all cpus are now online.
So the prerequisite for CONFIG_HAVE_MEMORYLESS_NODES is that there is an arch-specific set_numa_mem() that makes this mapping correct like ia64 does. If that's the case, then it's (1) completely undocumented and (2) Nishanth's patch is incomplete because anything that adds CONFIG_HAVE_MEMORYLESS_NODES needs to do the proper set_numa_mem() for it to be any different than numa_node_id().
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