Re: [PATCH 2/4] mm/slub: Use mem_node to allocate a new slab
From: Vlastimil Babka <hidden>
Date: 2020-03-17 13:34:30
Also in:
linux-mm
On 3/17/20 2:17 PM, Srikar Dronamraju wrote:
Currently while allocating a slab for a offline node, we use its associated node_numa_mem to search for a partial slab. If we don't find a partial slab, we try allocating a slab from the offline node using __alloc_pages_node. However this is bound to fail. NIP [c00000000039a300] __alloc_pages_nodemask+0x130/0x3b0 LR [c00000000039a3c4] __alloc_pages_nodemask+0x1f4/0x3b0 Call Trace: [c0000008b36837f0] [c00000000039a3b4] __alloc_pages_nodemask+0x1e4/0x3b0 (unreliable) [c0000008b3683870] [c0000000003d1ff8] new_slab+0x128/0xcf0 [c0000008b3683950] [c0000000003d6060] ___slab_alloc+0x410/0x820 [c0000008b3683a40] [c0000000003d64a4] __slab_alloc+0x34/0x60 [c0000008b3683a70] [c0000000003d78b0] __kmalloc_node+0x110/0x490 [c0000008b3683af0] [c000000000343a08] kvmalloc_node+0x58/0x110 [c0000008b3683b30] [c0000000003ffd44] mem_cgroup_css_online+0x104/0x270 [c0000008b3683b90] [c000000000234e08] online_css+0x48/0xd0 [c0000008b3683bc0] [c00000000023dedc] cgroup_apply_control_enable+0x2ec/0x4d0 [c0000008b3683ca0] [c0000000002416f8] cgroup_mkdir+0x228/0x5f0 [c0000008b3683d10] [c000000000520360] kernfs_iop_mkdir+0x90/0xf0 [c0000008b3683d50] [c00000000043e400] vfs_mkdir+0x110/0x230 [c0000008b3683da0] [c000000000441ee0] do_mkdirat+0xb0/0x1a0 [c0000008b3683e20] [c00000000000b278] system_call+0x5c/0x68 Mitigate this by allocating the new slab from the node_numa_mem.
Are you sure this is really needed and the other 3 patches are not enough for the current SLUB code to work as needed? It seems you are changing the semantics here...
quoted hunk ↗ jump to hunk
--- a/mm/slub.c +++ b/mm/slub.c@@ -1970,14 +1970,8 @@ static void *get_partial(struct kmem_cache *s, gfp_t flags, int node, struct kmem_cache_cpu *c) { void *object; - int searchnode = node; - if (node == NUMA_NO_NODE) - searchnode = numa_mem_id(); - else if (!node_present_pages(node)) - searchnode = node_to_mem_node(node); - - object = get_partial_node(s, get_node(s, searchnode), c, flags); + object = get_partial_node(s, get_node(s, node), c, flags); if (object || node != NUMA_NO_NODE)> return object; return get_any_partial(s, flags, c);
I.e. here in this if(), now node will never equal NUMA_NO_NODE (thanks to the hunk below), thus the get_any_partial() call becomes dead code?
quoted hunk ↗ jump to hunk
@@ -2470,6 +2464,11 @@ static inline void *new_slab_objects(struct kmem_cache *s, gfp_t flags, WARN_ON_ONCE(s->ctor && (flags & __GFP_ZERO)); + if (node == NUMA_NO_NODE) + node = numa_mem_id(); + else if (!node_present_pages(node)) + node = node_to_mem_node(node); + freelist = get_partial(s, flags, node, c); if (freelist)@@ -2569,12 +2568,10 @@ 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); + node = node_to_mem_node(node); - if (unlikely(!node_match(page, searchnode))) { + if (unlikely(!node_match(page, node))) { stat(s, ALLOC_NODE_MISMATCH); deactivate_slab(s, page, c->freelist, c); goto new_slab;