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ksm: reorganize ksm_check_stable_tree
Memory hotremove's ksm_check_stable_tree() is pitifully inefficient (restarting whenever it finds a stale node to remove), but rearrange so that at least it does not needlessly restart from nid 0 each time. And add a couple of comments: here is why we keep pfn instead of page. Signed-off-by: Hugh Dickins <hughd@google.com> Cc: Rik van Riel <riel@redhat.com> Cc: Petr Holasek <pholasek@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Izik Eidus <izik.eidus@ravellosystems.com> Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com> Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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38
mm/ksm.c
38
mm/ksm.c
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@ -1830,31 +1830,36 @@ void ksm_migrate_page(struct page *newpage, struct page *oldpage)
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#endif /* CONFIG_MIGRATION */
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#ifdef CONFIG_MEMORY_HOTREMOVE
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static struct stable_node *ksm_check_stable_tree(unsigned long start_pfn,
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unsigned long end_pfn)
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static void ksm_check_stable_tree(unsigned long start_pfn,
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unsigned long end_pfn)
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{
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struct stable_node *stable_node;
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struct rb_node *node;
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int nid;
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for (nid = 0; nid < nr_node_ids; nid++)
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for (node = rb_first(&root_stable_tree[nid]); node;
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node = rb_next(node)) {
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struct stable_node *stable_node;
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for (nid = 0; nid < nr_node_ids; nid++) {
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node = rb_first(&root_stable_tree[nid]);
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while (node) {
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stable_node = rb_entry(node, struct stable_node, node);
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if (stable_node->kpfn >= start_pfn &&
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stable_node->kpfn < end_pfn)
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return stable_node;
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stable_node->kpfn < end_pfn) {
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/*
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* Don't get_ksm_page, page has already gone:
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* which is why we keep kpfn instead of page*
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*/
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remove_node_from_stable_tree(stable_node);
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node = rb_first(&root_stable_tree[nid]);
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} else
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node = rb_next(node);
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cond_resched();
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}
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return NULL;
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}
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}
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static int ksm_memory_callback(struct notifier_block *self,
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unsigned long action, void *arg)
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{
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struct memory_notify *mn = arg;
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struct stable_node *stable_node;
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switch (action) {
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case MEM_GOING_OFFLINE:
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@ -1874,11 +1879,12 @@ static int ksm_memory_callback(struct notifier_block *self,
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/*
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* Most of the work is done by page migration; but there might
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* be a few stable_nodes left over, still pointing to struct
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* pages which have been offlined: prune those from the tree.
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* pages which have been offlined: prune those from the tree,
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* otherwise get_ksm_page() might later try to access a
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* non-existent struct page.
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*/
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while ((stable_node = ksm_check_stable_tree(mn->start_pfn,
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mn->start_pfn + mn->nr_pages)) != NULL)
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remove_node_from_stable_tree(stable_node);
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ksm_check_stable_tree(mn->start_pfn,
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mn->start_pfn + mn->nr_pages);
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/* fallthrough */
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case MEM_CANCEL_OFFLINE:
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