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ksm: reorganize ksm_check_stable_tree

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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>
This commit is contained in:
Hugh Dickins 2013-02-22 16:35:05 -08:00 committed by Linus Torvalds
parent e850dcf530
commit ee0ea59cf9
1 changed files with 22 additions and 16 deletions
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36
mm/ksm.c
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@ -1830,31 +1830,36 @@ void ksm_migrate_page(struct page *newpage, struct page *oldpage)
#endif /* CONFIG_MIGRATION */ #endif /* CONFIG_MIGRATION */
#ifdef CONFIG_MEMORY_HOTREMOVE #ifdef CONFIG_MEMORY_HOTREMOVE
static struct stable_node *ksm_check_stable_tree(unsigned long start_pfn, static void ksm_check_stable_tree(unsigned long start_pfn,
unsigned long end_pfn) unsigned long end_pfn)
{ {
struct stable_node *stable_node;
struct rb_node *node; struct rb_node *node;
int nid; int nid;
for (nid = 0; nid < nr_node_ids; nid++) for (nid = 0; nid < nr_node_ids; nid++) {
for (node = rb_first(&root_stable_tree[nid]); node; node = rb_first(&root_stable_tree[nid]);
node = rb_next(node)) { while (node) {
struct stable_node *stable_node;
stable_node = rb_entry(node, struct stable_node, node); stable_node = rb_entry(node, struct stable_node, node);
if (stable_node->kpfn >= start_pfn && if (stable_node->kpfn >= start_pfn &&
stable_node->kpfn < end_pfn) stable_node->kpfn < end_pfn) {
return stable_node; /*
* 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, static int ksm_memory_callback(struct notifier_block *self,
unsigned long action, void *arg) unsigned long action, void *arg)
{ {
struct memory_notify *mn = arg; struct memory_notify *mn = arg;
struct stable_node *stable_node;
switch (action) { switch (action) {
case MEM_GOING_OFFLINE: 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 * Most of the work is done by page migration; but there might
* be a few stable_nodes left over, still pointing to struct * 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, ksm_check_stable_tree(mn->start_pfn,
mn->start_pfn + mn->nr_pages)) != NULL) mn->start_pfn + mn->nr_pages);
remove_node_from_stable_tree(stable_node);
/* fallthrough */ /* fallthrough */
case MEM_CANCEL_OFFLINE: case MEM_CANCEL_OFFLINE: