On 3/18/20 5:06 PM, Bharata B Rao wrote: > On Wed, Mar 18, 2020 at 03:42:19PM +0100, Vlastimil Babka wrote: >> This is a PowerPC platform with following NUMA topology: >> >> available: 2 nodes (0-1) >> node 0 cpus: >> node 0 size: 0 MB >> node 0 free: 0 MB >> node 1 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 >> node 1 size: 35247 MB >> node 1 free: 30907 MB >> node distances: >> node 0 1 >> 0: 10 40 >> 1: 40 10 >> >> possible numa nodes: 0-31 >> >> A related issue was reported by Bharata [3] where a similar PowerPC >> configuration, but without patch [2] ends up allocating large amounts of pages >> by kmalloc-1k kmalloc-512. This seems to have the same underlying issue with >> node_to_mem_node() not behaving as expected, and might probably also lead >> to an infinite loop with CONFIG_SLUB_CPU_PARTIAL. > > This patch doesn't fix the issue of kmalloc caches consuming more > memory for the above mentioned topology. Also CONFIG_SLUB_CPU_PARTIAL is set > here and I have not observed infinite loop till now. OK that means something is wrong with my analysis. > Or, are you expecting your fix to work on top of Srikar's other patchset > https://lore.kernel.org/linuxppc-dev/20200311110237.5731-1-srikar@xxxxxxxxxxxxxxxxxx/t/#u ? No, I hoped it would work on mainline. > With the above patchset, no fix is required to address increased memory > consumption of kmalloc caches because this patchset prevents such > topology from occuring thereby making it impossible for the problem > to surface (or at least impossible for the specific topology that I > mentioned) Right, I hope to fix it nevertheless. >> diff --git a/mm/slub.c b/mm/slub.c >> index 17dc00e33115..4d798cacdae1 100644 >> --- a/mm/slub.c >> +++ b/mm/slub.c >> @@ -1511,7 +1511,7 @@ static inline struct page *alloc_slab_page(struct kmem_cache *s, >> struct page *page; >> unsigned int order = oo_order(oo); >> >> - if (node == NUMA_NO_NODE) >> + if (node == NUMA_NO_NODE || !node_online(node)) >> page = alloc_pages(flags, order); >> else >> page = __alloc_pages_node(node, flags, order); >> @@ -1973,8 +1973,6 @@ static void *get_partial(struct kmem_cache *s, gfp_t flags, int node, >> >> if (node == NUMA_NO_NODE) >> searchnode = numa_mem_id(); >> - else if (!node_present_pages(node)) >> - searchnode = node_to_mem_node(node); > > We still come here with memory-less node=0 (and not NUMA_NO_NODE), fail to > find partial slab, go back and allocate a new one thereby continuosly > increasing the number of newly allocated slabs. > >> >> object = get_partial_node(s, get_node(s, searchnode), c, flags); >> if (object || node != NUMA_NO_NODE) >> @@ -2568,12 +2566,15 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, >> redo: >> >> if (unlikely(!node_match(page, node))) { >> - int searchnode = node; >> - >> - if (node != NUMA_NO_NODE && !node_present_pages(node)) >> - searchnode = node_to_mem_node(node); >> - >> - if (unlikely(!node_match(page, searchnode))) { >> + /* >> + * node_match() false implies node != NUMA_NO_NODE >> + * but if the node is not online or has no pages, just >> + * ignore the constraint >> + */ >> + if ((!node_online(node) || !node_present_pages(node))) { >> + node = NUMA_NO_NODE; >> + goto redo; > > Many calls for allocating slab object from memory-less node 0 in my case > don't even hit the above check because they get short circuited by > goto new_slab label which is present a few lines above. Hence I don't see > any reduction in the amount of slab memory with this fix. Thanks a lot for the info, I will try again :) > Regards, > Bharata. >
