On Wed, 29 Jan 2014, Nishanth Aravamudan wrote: > exactly what the caller intends. > > int searchnode = node; > if (node == NUMA_NO_NODE) > searchnode = numa_mem_id(); > if (!node_present_pages(node)) > searchnode = local_memory_node(node); > > The difference in semantics from the previous is that here, if we have a > memoryless node, rather than using the CPU's nearest NUMA node, we use > the NUMA node closest to the requested one?
The idea here is that the page allocator will do the fallback to other nodes. This check for !node_present should not be necessary. SLUB needs to accept the page from whatever node the page allocator returned and work with that. The problem is the check for having a slab from the "right" node may fall again after another attempt to allocate from the same node. SLUB will then push the slab from the *wrong* node back to the partial lists and may attempt another allocation that will again be successful but return memory from another node. That way the partial lists from a particular node are growing uselessly. One way to solve this may be to check if memory is actually allocated from the requested node and fallback to NUMA_NO_NODE (which will use the last allocated slab) for future allocs if the page allocator returned memory from a different node (unless GFP_THIS_NODE is set of course). Otherwise we end up replicating the page allocator logic in slub like in slab. That is what I wanted to avoid. _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
