The patch titled
Subject: ksm: reorganize ksm_check_stable_tree
has been added to the -mm tree. Its filename is
ksm-reorganize-ksm_check_stable_tree.patch
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From: Hugh Dickins <hughd@xxxxxxxxxx>
Subject: 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@xxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Petr Holasek <pholasek@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Izik Eidus <izik.eidus@xxxxxxxxxxxxxxxxxx>
Cc: Gerald Schaefer <gerald.schaefer@xxxxxxxxxx>
Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/ksm.c | 38 ++++++++++++++++++++++----------------
1 file changed, 22 insertions(+), 16 deletions(-)
diff -puN mm/ksm.c~ksm-reorganize-ksm_check_stable_tree mm/ksm.c
--- a/mm/ksm.c~ksm-reorganize-ksm_check_stable_tree
+++ a/mm/ksm.c
@@ -1830,31 +1830,36 @@ void ksm_migrate_page(struct page *newpa
#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 no
/*
* 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:
_
Patches currently in -mm which might be from hughd@xxxxxxxxxx are
linux-next.patch
revert-x86-mm-make-spurious_fault-check-explicitly-check-the-present-bit.patch
pageattr-prevent-pse-and-gloabl-leftovers-to-confuse-pmd-pte_present-and-pmd_huge.patch
mm-memcg-only-evict-file-pages-when-we-have-plenty.patch
mm-vmscan-save-work-scanning-almost-empty-lru-lists.patch
mm-vmscan-clarify-how-swappiness-highest-priority-memcg-interact.patch
mm-vmscan-improve-comment-on-low-page-cache-handling.patch
mm-vmscan-clean-up-get_scan_count.patch
mm-vmscan-clean-up-get_scan_count-fix.patch
mm-vmscan-compaction-works-against-zones-not-lruvecs.patch
mm-vmscan-compaction-works-against-zones-not-lruvecs-fix.patch
mm-reduce-rmap-overhead-for-ex-ksm-page-copies-created-on-swap-faults.patch
mm-page_allocc-__setup_per_zone_wmarks-make-min_pages-unsigned-long.patch
mm-vmscanc-__zone_reclaim-replace-max_t-with-max.patch
mmksm-use-new-hashtable-implementation.patch
mm-make-madvisemadv_willneed-support-swap-file-prefetch.patch
mm-make-madvisemadv_willneed-support-swap-file-prefetch-fix.patch
mm-make-madvisemadv_willneed-support-swap-file-prefetch-fix-fix.patch
mm-avoid-calling-pgdat_balanced-needlessly.patch
mm-numa-fix-minor-typo-in-numa_next_scan.patch
mm-numa-take-thp-into-account-when-migrating-pages-for-numa-balancing.patch
mm-numa-handle-side-effects-in-count_vm_numa_events-for-config_numa_balancing.patch
mm-move-page-flags-layout-to-separate-header.patch
mm-fold-page-_last_nid-into-page-flags-where-possible.patch
mm-numa-cleanup-flow-of-transhuge-page-migration.patch
mm-dont-inline-page_mapping.patch
swap-make-each-swap-partition-have-one-address_space.patch
swap-make-each-swap-partition-have-one-address_space-fix.patch
swap-add-per-partition-lock-for-swapfile.patch
memcg-reduce-the-size-of-struct-memcg-244-fold.patch
memcg-reduce-the-size-of-struct-memcg-244-fold-fix.patch
ksm-allow-trees-per-numa-node.patch
ksm-add-sysfs-abi-documentation.patch
ksm-trivial-tidyups.patch
ksm-reorganize-ksm_check_stable_tree.patch
ksm-get_ksm_page-locked.patch
ksm-remove-old-stable-nodes-more-thoroughly.patch
ksm-make-ksm-page-migration-possible.patch
ksm-make-merge_across_nodes-migration-safe.patch
ksm-enable-ksm-page-migration.patch
mm-remove-offlining-arg-to-migrate_pages.patch
ksm-stop-hotremove-lockdep-warning.patch
mm-prevent-addition-of-pages-to-swap-if-may_writepage-is-unset.patch
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