Messages in this thread | | | Date | Fri, 11 Jul 2014 10:55:59 -0500 (CDT) | From | Christoph Lameter <> | Subject | Re: [RFC Patch V1 07/30] mm: Use cpu_to_mem()/numa_mem_id() to support memoryless node |
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On Fri, 11 Jul 2014, Tejun Heo wrote:
> On Fri, Jul 11, 2014 at 11:21:56AM -0400, Tejun Heo wrote: > > Even if that's the case, there's no reason to burden everyone with > > this distinction. Most users just wanna say "I'm on this node. > > Please allocate considering that". There's nothing wrong with using > > numa_node_id() for that. > > Also, this is minor but don't we also lose fallback information by > doing this from the caller? Please consider the following topology > where each hop is the same distance. > > A - B - X - C - D > > Where X is the memless node. num_mem_id() on X would return either B > or C, right? If B or C can't satisfy the allocation, the allocator > would fallback to A from B and D for C, both of which aren't optimal. > It should first fall back to C or B respectively, which the allocator > can't do anymoe because the information is lost when the caller side > performs numa_mem_id().
True but the advantage is that the numa_mem_id() allows the use of a consitent sort of "local" node which increases allocator performance due to the abillity to cache objects from that node.
> Seems pretty misguided to me.
IMHO the whole concept of a memoryless node looks pretty misguided to me.
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