Messages in this thread | | | Subject | Re: [RFC 1/2] slub: Avoid trying to allocate memory on offline nodes | From | Jeremy Linton <> | Date | Thu, 2 Aug 2018 22:21:53 -0500 |
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Hi,
On 08/02/2018 04:15 AM, Michal Hocko wrote: > On Wed 01-08-18 15:04:17, Jeremy Linton wrote: > [...] >> @@ -2519,6 +2519,8 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, >> if (unlikely(!node_match(page, searchnode))) { >> stat(s, ALLOC_NODE_MISMATCH); >> deactivate_slab(s, page, c->freelist, c); >> + if (!node_online(searchnode)) >> + node = NUMA_NO_NODE; >> goto new_slab; > > This is inherently racy. Numa node can get offline at any point after > you check it here. Making it race free would involve some sort of > locking and I am not really convinced this is a good idea.
I spent some time looking/thinking about this, and i'm pretty sure its not creating any new problems. But OTOH, I think the node_online() check is probably a bit misleading as what we really want to assure is that node<MAX_NUMNODES and that there is going to be a valid entry in NODE_DATA() so we don't deference null.
> >> } >> } >> -- >> 2.14.3 >> >
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