Vlastimil correctly pointed out that when a fast search fails and cc->migrate_pfn is reinitialised to the lowest PFN found that the caller does not use the updated PFN.
He also pointed out that there is an inconsistency between move_freelist_head and move_freelist_tail. This patch adds a new helper and uses it in move_freelist_tail so that list manipulations are avoided if the first list item traversed is a suitable migration source. The end result will be that the helpers should be symmetrical and it's been confirmed that the scan rates are slightly improved as a result of the fix but not enough to rewrite the changelogs. This is a fix for the mmotm patch mm-compaction-use-free-lists-to-quickly-locate-a-migration-source.patch . It's been provided as a combined patch as the first patch is not picked up at the time of writing and a rolled up patch is less likely to fall through the cracks. Signed-off-by: Mel Gorman <[email protected]> --- drivers/gpu/drm/i915/i915_utils.h | 6 ------ include/linux/list.h | 11 +++++++++++ mm/compaction.c | 10 ++++++---- 3 files changed, 17 insertions(+), 10 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_utils.h b/drivers/gpu/drm/i915/i915_utils.h index 9726df37c4c4..540e20eb032c 100644 --- a/drivers/gpu/drm/i915/i915_utils.h +++ b/drivers/gpu/drm/i915/i915_utils.h @@ -123,12 +123,6 @@ static inline u64 ptr_to_u64(const void *ptr) #include <linux/list.h> -static inline int list_is_first(const struct list_head *list, - const struct list_head *head) -{ - return head->next == list; -} - static inline void __list_del_many(struct list_head *head, struct list_head *first) { diff --git a/include/linux/list.h b/include/linux/list.h index edb7628e46ed..79626b5ab36c 100644 --- a/include/linux/list.h +++ b/include/linux/list.h @@ -206,6 +206,17 @@ static inline void list_bulk_move_tail(struct list_head *head, head->prev = last; } +/** + * list_is_first -- tests whether @ list is the first entry in list @head + * @list: the entry to test + * @head: the head of the list + */ +static inline int list_is_first(const struct list_head *list, + const struct list_head *head) +{ + return list->prev == head; +} + /** * list_is_last - tests whether @list is the last entry in list @head * @list: the entry to test diff --git a/mm/compaction.c b/mm/compaction.c index 92d10eb3d1c7..55f7ab142af2 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -1062,7 +1062,7 @@ move_freelist_tail(struct list_head *freelist, struct page *freepage) { LIST_HEAD(sublist); - if (!list_is_last(freelist, &freepage->lru)) { + if (!list_is_first(freelist, &freepage->lru)) { list_cut_position(&sublist, freelist, &freepage->lru); if (!list_empty(&sublist)) list_splice_tail(&sublist, freelist); @@ -1238,14 +1238,16 @@ update_fast_start_pfn(struct compact_control *cc, unsigned long pfn) cc->fast_start_pfn = min(cc->fast_start_pfn, pfn); } -static inline void +static inline unsigned long reinit_migrate_pfn(struct compact_control *cc) { if (!cc->fast_start_pfn || cc->fast_start_pfn == ULONG_MAX) - return; + return cc->migrate_pfn; cc->migrate_pfn = cc->fast_start_pfn; cc->fast_start_pfn = ULONG_MAX; + + return cc->migrate_pfn; } /* @@ -1361,7 +1363,7 @@ static unsigned long fast_find_migrateblock(struct compact_control *cc) * that had free pages as the basis for starting a linear scan. */ if (pfn == cc->migrate_pfn) - reinit_migrate_pfn(cc); + pfn = reinit_migrate_pfn(cc); return pfn; }
