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hugetlb, memory_hotplug: prefer to use reserved pages for migration

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new_node_page will try to use the origin's next NUMA node as the
migration destination for hugetlb pages.  If such a node doesn't have
any preallocated pool it falls back to __alloc_buddy_huge_page_no_mpol
to allocate a surplus page instead.  This is quite subotpimal for any
configuration when hugetlb pages are no distributed to all NUMA nodes
evenly.  Say we have a hotplugable node 4 and spare hugetlb pages are
node 0

  /sys/devices/system/node/node0/hugepages/hugepages-2048kB/nr_hugepages:10000
  /sys/devices/system/node/node1/hugepages/hugepages-2048kB/nr_hugepages:0
  /sys/devices/system/node/node2/hugepages/hugepages-2048kB/nr_hugepages:0
  /sys/devices/system/node/node3/hugepages/hugepages-2048kB/nr_hugepages:0
  /sys/devices/system/node/node4/hugepages/hugepages-2048kB/nr_hugepages:10000
  /sys/devices/system/node/node5/hugepages/hugepages-2048kB/nr_hugepages:0
  /sys/devices/system/node/node6/hugepages/hugepages-2048kB/nr_hugepages:0
  /sys/devices/system/node/node7/hugepages/hugepages-2048kB/nr_hugepages:0

Now we consume the whole pool on node 4 and try to offline this node.
All the allocated pages should be moved to node0 which has enough
preallocated pages to hold them.  With the current implementation
offlining very likely fails because hugetlb allocations during runtime
are much less reliable.

Fix this by reusing the nodemask which excludes migration source and try
to find a first node which has a page in the preallocated pool first and
fall back to __alloc_buddy_huge_page_no_mpol only when the whole pool is
consumed.

[[email protected]: remove bogus arg from alloc_huge_page_nodemask() stub]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Michal Hocko <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Cc: Naoya Horiguchi <[email protected]>
Cc: Xishi Qiu <[email protected]>
Cc: zhong jiang <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Michal Hocko 2017-07-10 15:48:44 -07:00 • committed by Linus Torvalds
commit 4db9b2efe9
3 changed files with 31 additions and 7 deletions
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27
mm/hugetlb.c
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@ -1723,6 +1723,33 @@ struct page *alloc_huge_page_node(struct hstate *h, int nid)
return page;
}
struct page *alloc_huge_page_nodemask(struct hstate *h, const nodemask_t *nmask)
{
struct page *page = NULL;
int node;
spin_lock(&hugetlb_lock);
if (h->free_huge_pages - h->resv_huge_pages > 0) {
for_each_node_mask(node, *nmask) {
page = dequeue_huge_page_node_exact(h, node);
if (page)
break;
}
}
spin_unlock(&hugetlb_lock);
if (page)
return page;
/* No reservations, try to overcommit */
for_each_node_mask(node, *nmask) {
page = __alloc_buddy_huge_page_no_mpol(h, node);
if (page)
return page;
}
return NULL;
}
/*
* Increase the hugetlb pool such that it can accommodate a reservation
* of size 'delta'.

9
mm/memory_hotplug.c
View file

@ -1446,14 +1446,9 @@ static struct page *new_node_page(struct page *page, unsigned long private,
if (nodes_empty(nmask))
node_set(nid, nmask);
/*
* TODO: allocate a destination hugepage from a nearest neighbor node,
* accordance with memory policy of the user process if possible. For
* now as a simple work-around, we use the next node for destination.
*/
if (PageHuge(page))
return alloc_huge_page_node(page_hstate(compound_head(page)),
next_node_in(nid, nmask));
return alloc_huge_page_nodemask(
page_hstate(compound_head(page)), &nmask);
if (PageHighMem(page)
|| (zone_idx(page_zone(page)) == ZONE_MOVABLE))