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author | Hugh Dickins <hughd@google.com> | 2013-02-22 16:35:05 -0800 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-02-23 17:50:19 -0800 |
commit | ee0ea59cf9ea95369d686bdc4b3d8c027e2b99cd (patch) | |
tree | 31b446ae45861baf9532d94bffcc091933f7df95 | |
parent | e850dcf530a470b6115344ee00acf766d824db53 (diff) | |
download | linux-ee0ea59cf9ea95369d686bdc4b3d8c027e2b99cd.tar.bz2 |
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>
-rw-r--r-- | mm/ksm.c | 38 |
1 files changed, 22 insertions, 16 deletions
@@ -1830,31 +1830,36 @@ void ksm_migrate_page(struct page *newpage, struct page *oldpage) #endif /* CONFIG_MIGRATION */ #ifdef CONFIG_MEMORY_HOTREMOVE -static struct stable_node *ksm_check_stable_tree(unsigned long start_pfn, - unsigned long end_pfn) +static void ksm_check_stable_tree(unsigned long start_pfn, + unsigned long end_pfn) { + struct stable_node *stable_node; struct rb_node *node; int nid; - for (nid = 0; nid < nr_node_ids; nid++) - for (node = rb_first(&root_stable_tree[nid]); node; - node = rb_next(node)) { - struct stable_node *stable_node; - + for (nid = 0; nid < nr_node_ids; nid++) { + node = rb_first(&root_stable_tree[nid]); + while (node) { stable_node = rb_entry(node, struct stable_node, node); if (stable_node->kpfn >= start_pfn && - stable_node->kpfn < end_pfn) - return stable_node; + stable_node->kpfn < end_pfn) { + /* + * Don't get_ksm_page, page has already gone: + * which is why we keep kpfn instead of page* + */ + remove_node_from_stable_tree(stable_node); + node = rb_first(&root_stable_tree[nid]); + } else + node = rb_next(node); + cond_resched(); } - - return NULL; + } } static int ksm_memory_callback(struct notifier_block *self, unsigned long action, void *arg) { struct memory_notify *mn = arg; - struct stable_node *stable_node; switch (action) { case MEM_GOING_OFFLINE: @@ -1874,11 +1879,12 @@ static int ksm_memory_callback(struct notifier_block *self, /* * Most of the work is done by page migration; but there might * be a few stable_nodes left over, still pointing to struct - * pages which have been offlined: prune those from the tree. + * pages which have been offlined: prune those from the tree, + * otherwise get_ksm_page() might later try to access a + * non-existent struct page. */ - while ((stable_node = ksm_check_stable_tree(mn->start_pfn, - mn->start_pfn + mn->nr_pages)) != NULL) - remove_node_from_stable_tree(stable_node); + ksm_check_stable_tree(mn->start_pfn, + mn->start_pfn + mn->nr_pages); /* fallthrough */ case MEM_CANCEL_OFFLINE: |