On 05.02.2014 [13:28:03 -0600], Christoph Lameter wrote: > On Tue, 4 Feb 2014, Nishanth Aravamudan wrote: > > > > If the target node allocation fails (for whatever reason) then I would > > > recommend for simplicities sake to change the target node to > > > NUMA_NO_NODE and just take whatever is in the current cpu slab. A more > > > complex solution would be to look through partial lists in increasing > > > distance to find a partially used slab that is reasonable close to the > > > current node. Slab has logic like that in fallback_alloc(). Slubs > > > get_any_partial() function does something close to what you want. > > > > I apologize for my own ignorance, but I'm having trouble following. > > Anton's original patch did fallback to the current cpu slab, but I'm not > > sure any NUMA_NO_NODE change is necessary there. At the point we're > > deactivating the slab (in the current code, in __slab_alloc()), we have > > successfully allocated from somewhere, it's just not on the node we > > expected to be on. > > Right so if we are ignoring the node then the simplest thing to do is to > not deactivate the current cpu slab but to take an object from it. Ok, that's what Anton's patch does, I believe. Are you ok with that patch as it is? > > So perhaps you are saying to make a change lower in the code? I'm not > > sure where it makes sense to change the target node in that case. I'd > > appreciate any guidance you can give. > > This not an easy thing to do. If the current slab is not the right node > but would be the node from which the page allocator would be returning > memory then the current slab can still be allocated from. If the fallback > is to another node then the current cpu slab needs to be deactivated and > the allocation from that node needs to proceeed. Have a look at > fallback_alloc() in the slab allocator. > > A allocation attempt from the page allocator can be restricted to a > specific node through GFP_THIS_NODE. Thanks for the pointers, I will try and take a look. Thanks, Nish -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>