On Tue, Jan 07, 2014 at 06:31:56PM +0900, Joonsoo Kim wrote: >On Tue, Jan 07, 2014 at 05:21:45PM +0800, Wanpeng Li wrote: >> On Tue, Jan 07, 2014 at 06:10:16PM +0900, Joonsoo Kim wrote: >> >On Tue, Jan 07, 2014 at 04:48:40PM +0800, Wanpeng Li wrote: >> >> Hi Joonsoo, >> >> On Tue, Jan 07, 2014 at 04:41:36PM +0900, Joonsoo Kim wrote: >> >> >On Tue, Jan 07, 2014 at 01:21:00PM +1100, Anton Blanchard wrote: >> >> >> >> >> [...] >> >> >Hello, >> >> > >> >> >I think that we need more efforts to solve unbalanced node problem. >> >> > >> >> >With this patch, even if node of current cpu slab is not favorable to >> >> >unbalanced node, allocation would proceed and we would get the unintended memory. >> >> > >> >> >> >> We have a machine: >> >> >> >> [ 0.000000] Node 0 Memory: >> >> [ 0.000000] Node 4 Memory: 0x0-0x10000000 0x20000000-0x60000000 0x80000000-0xc0000000 >> >> [ 0.000000] Node 6 Memory: 0x10000000-0x20000000 0x60000000-0x80000000 >> >> [ 0.000000] Node 10 Memory: 0xc0000000-0x180000000 >> >> >> >> [ 0.041486] Node 0 CPUs: 0-19 >> >> [ 0.041490] Node 4 CPUs: >> >> [ 0.041492] Node 6 CPUs: >> >> [ 0.041495] Node 10 CPUs: >> >> >> >> The pages of current cpu slab should be allocated from fallback zones/nodes >> >> of the memoryless node in buddy system, how can not favorable happen? >> > >> >Hi, Wanpeng. >> > >> >IIRC, if we call kmem_cache_alloc_node() with certain node #, we try to >> >allocate the page in fallback zones/node of that node #. So fallback list isn't >> >related to fallback one of memoryless node #. Am I wrong? >> > >> >> Anton add node_spanned_pages(node) check, so current cpu slab mentioned >> above is against memoryless node. If I miss something? > >I thought following scenario. > >memoryless node # : 1 >1's fallback node # : 0 > >On node 1's cpu, > >1. kmem_cache_alloc_node (node 2) >2. allocate the page on node 2 for the slab, now cpu slab is that one. >3. kmem_cache_alloc_node (local node, that is, node 1) >4. It check node_spanned_pages() and find it is memoryless node. >So return node 2's memory. > >Is it impossible scenario? > Indeed, it can happen. Regards, Wanpeng Li >Thanks. -- 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>