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 Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ 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 -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html