Messages in this thread | | | Date | Mon, 28 Sep 2015 09:50:18 +0800 | From | Tang Chen <> | Subject | Re: [PATCH v2 3/7] x86, gfp: Cache best near node for memory allocation. |
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Hi, tj,
On 09/27/2015 01:53 AM, Tejun Heo wrote: > Hello, Tang. > > On Sat, Sep 26, 2015 at 05:31:07PM +0800, Tang Chen wrote: >>>> @@ -307,13 +307,19 @@ static inline struct page *alloc_pages_node(int nid, gfp_t gfp_mask, >>>> if (nid < 0) >>>> nid = numa_node_id(); >>>> + if (!node_online(nid)) >>>> + nid = get_near_online_node(nid); >>>> + >>>> return __alloc_pages(gfp_mask, order, node_zonelist(nid, gfp_mask)); >>>> } >>> Why not just update node_data[]->node_zonelist in the first place? >> zonelist will be rebuilt in __offline_pages() when the zone is not populated >> any more. >> >> Here, getting the best near online node is for those cpus on memory-less >> nodes. >> >> In the original code, if nid is NUMA_NO_NODE, the node the current cpu >> resides in >> will be chosen. And if the node is memory-less node, the cpu will be mapped >> to its >> best near online node. >> >> But this patch-set will map the cpu to its original node, so numa_node_id() >> may return >> a memory-less node to allocator. And then memory allocation may fail. > Correct me if I'm wrong but the zonelist dictates which memory areas > the page allocator is gonna try to from, right? What I'm wondering is > why we aren't handling memory-less nodes by simply updating their > zonelists. I mean, if, say, node 2 is memory-less, its zonelist can > simply point to zones from other nodes, right? What am I missing > here?
Oh, yes, you are right. But I remember some time ago, Liu, Jiang has or was going to handle memory less node like this in his patch:
https://lkml.org/lkml/2015/8/16/130
BTW, to Liu Jiang, how is your patches going on ?
Thanks.
> > Thanks. >
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