1 files changed, 258 insertions, 0 deletions
diff --git a/include/linux/compaction.h b/include/linux/compaction.h
new file mode 100644
index 000000000..1de5a1151
--- /dev/null
+++ b/include/linux/compaction.h
@@ -0,0 +1,258 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_COMPACTION_H
+#define _LINUX_COMPACTION_H
+
+/*
+ * Determines how hard direct compaction should try to succeed.
+ * Lower value means higher priority, analogically to reclaim priority.
+ */
+enum compact_priority {
+	COMPACT_PRIO_SYNC_FULL,
+	MIN_COMPACT_PRIORITY = COMPACT_PRIO_SYNC_FULL,
+	COMPACT_PRIO_SYNC_LIGHT,
+	MIN_COMPACT_COSTLY_PRIORITY = COMPACT_PRIO_SYNC_LIGHT,
+	DEF_COMPACT_PRIORITY = COMPACT_PRIO_SYNC_LIGHT,
+	COMPACT_PRIO_ASYNC,
+	INIT_COMPACT_PRIORITY = COMPACT_PRIO_ASYNC
+};
+
+/* Return values for compact_zone() and try_to_compact_pages() */
+/* When adding new states, please adjust include/trace/events/compaction.h */
+enum compact_result {
+	/* For more detailed tracepoint output - internal to compaction */
+	COMPACT_NOT_SUITABLE_ZONE,
+	/*
+	 * compaction didn't start as it was not possible or direct reclaim
+	 * was more suitable
+	 */
+	COMPACT_SKIPPED,
+	/* compaction didn't start as it was deferred due to past failures */
+	COMPACT_DEFERRED,
+
+	/* For more detailed tracepoint output - internal to compaction */
+	COMPACT_NO_SUITABLE_PAGE,
+	/* compaction should continue to another pageblock */
+	COMPACT_CONTINUE,
+
+	/*
+	 * The full zone was compacted scanned but wasn't successfull to compact
+	 * suitable pages.
+	 */
+	COMPACT_COMPLETE,
+	/*
+	 * direct compaction has scanned part of the zone but wasn't successfull
+	 * to compact suitable pages.
+	 */
+	COMPACT_PARTIAL_SKIPPED,
+
+	/* compaction terminated prematurely due to lock contentions */
+	COMPACT_CONTENDED,
+
+	/*
+	 * direct compaction terminated after concluding that the allocation
+	 * should now succeed
+	 */
+	COMPACT_SUCCESS,
+};
+
+struct alloc_context; /* in mm/internal.h */
+
+/*
+ * Number of free order-0 pages that should be available above given watermark
+ * to make sure compaction has reasonable chance of not running out of free
+ * pages that it needs to isolate as migration target during its work.
+ */
+static inline unsigned long compact_gap(unsigned int order)
+{
+	/*
+	 * Although all the isolations for migration are temporary, compaction
+	 * free scanner may have up to 1 << order pages on its list and then
+	 * try to split an (order - 1) free page. At that point, a gap of
+	 * 1 << order might not be enough, so it's safer to require twice that
+	 * amount. Note that the number of pages on the list is also
+	 * effectively limited by COMPACT_CLUSTER_MAX, as that's the maximum
+	 * that the migrate scanner can have isolated on migrate list, and free
+	 * scanner is only invoked when the number of isolated free pages is
+	 * lower than that. But it's not worth to complicate the formula here
+	 * as a bigger gap for higher orders than strictly necessary can also
+	 * improve chances of compaction success.
+	 */
+	return 2UL << order;
+}
+
+#ifdef CONFIG_COMPACTION
+extern int sysctl_compact_memory;
+extern unsigned int sysctl_compaction_proactiveness;
+extern int sysctl_compaction_handler(struct ctl_table *table, int write,
+			void *buffer, size_t *length, loff_t *ppos);
+extern int sysctl_extfrag_threshold;
+extern int sysctl_compact_unevictable_allowed;
+
+extern unsigned int extfrag_for_order(struct zone *zone, unsigned int order);
+extern int fragmentation_index(struct zone *zone, unsigned int order);
+extern enum compact_result try_to_compact_pages(gfp_t gfp_mask,
+		unsigned int order, unsigned int alloc_flags,
+		const struct alloc_context *ac, enum compact_priority prio,
+		struct page **page);
+extern void reset_isolation_suitable(pg_data_t *pgdat);
+extern enum compact_result compaction_suitable(struct zone *zone, int order,
+		unsigned int alloc_flags, int highest_zoneidx);
+
+extern void defer_compaction(struct zone *zone, int order);
+extern bool compaction_deferred(struct zone *zone, int order);
+extern void compaction_defer_reset(struct zone *zone, int order,
+				bool alloc_success);
+extern bool compaction_restarting(struct zone *zone, int order);
+
+/* Compaction has made some progress and retrying makes sense */
+static inline bool compaction_made_progress(enum compact_result result)
+{
+	/*
+	 * Even though this might sound confusing this in fact tells us
+	 * that the compaction successfully isolated and migrated some
+	 * pageblocks.
+	 */
+	if (result == COMPACT_SUCCESS)
+		return true;
+
+	return false;
+}
+
+/* Compaction has failed and it doesn't make much sense to keep retrying. */
+static inline bool compaction_failed(enum compact_result result)
+{
+	/* All zones were scanned completely and still not result. */
+	if (result == COMPACT_COMPLETE)
+		return true;
+
+	return false;
+}
+
+/* Compaction needs reclaim to be performed first, so it can continue. */
+static inline bool compaction_needs_reclaim(enum compact_result result)
+{
+	/*
+	 * Compaction backed off due to watermark checks for order-0
+	 * so the regular reclaim has to try harder and reclaim something.
+	 */
+	if (result == COMPACT_SKIPPED)
+		return true;
+
+	return false;
+}
+
+/*
+ * Compaction has backed off for some reason after doing some work or none
+ * at all. It might be throttling or lock contention. Retrying might be still
+ * worthwhile, but with a higher priority if allowed.
+ */
+static inline bool compaction_withdrawn(enum compact_result result)
+{
+	/*
+	 * If compaction is deferred for high-order allocations, it is
+	 * because sync compaction recently failed. If this is the case
+	 * and the caller requested a THP allocation, we do not want
+	 * to heavily disrupt the system, so we fail the allocation
+	 * instead of entering direct reclaim.
+	 */
+	if (result == COMPACT_DEFERRED)
+		return true;
+
+	/*
+	 * If compaction in async mode encounters contention or blocks higher
+	 * priority task we back off early rather than cause stalls.
+	 */
+	if (result == COMPACT_CONTENDED)
+		return true;
+
+	/*
+	 * Page scanners have met but we haven't scanned full zones so this
+	 * is a back off in fact.
+	 */
+	if (result == COMPACT_PARTIAL_SKIPPED)
+		return true;
+
+	return false;
+}
+
+
+bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
+					int alloc_flags);
+
+extern int kcompactd_run(int nid);
+extern void kcompactd_stop(int nid);
+extern void wakeup_kcompactd(pg_data_t *pgdat, int order, int highest_zoneidx);
+
+#else
+static inline void reset_isolation_suitable(pg_data_t *pgdat)
+{
+}
+
+static inline enum compact_result compaction_suitable(struct zone *zone, int order,
+					int alloc_flags, int highest_zoneidx)
+{
+	return COMPACT_SKIPPED;
+}
+
+static inline void defer_compaction(struct zone *zone, int order)
+{
+}
+
+static inline bool compaction_deferred(struct zone *zone, int order)
+{
+	return true;
+}
+
+static inline bool compaction_made_progress(enum compact_result result)
+{
+	return false;
+}
+
+static inline bool compaction_failed(enum compact_result result)
+{
+	return false;
+}
+
+static inline bool compaction_needs_reclaim(enum compact_result result)
+{
+	return false;
+}
+
+static inline bool compaction_withdrawn(enum compact_result result)
+{
+	return true;
+}
+
+static inline int kcompactd_run(int nid)
+{
+	return 0;
+}
+static inline void kcompactd_stop(int nid)
+{
+}
+
+static inline void wakeup_kcompactd(pg_data_t *pgdat,
+				int order, int highest_zoneidx)
+{
+}
+
+#endif /* CONFIG_COMPACTION */
+
+struct node;
+#if defined(CONFIG_COMPACTION) && defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
+extern int compaction_register_node(struct node *node);
+extern void compaction_unregister_node(struct node *node);
+
+#else
+
+static inline int compaction_register_node(struct node *node)
+{
+	return 0;
+}
+
+static inline void compaction_unregister_node(struct node *node)
+{
+}
+#endif /* CONFIG_COMPACTION && CONFIG_SYSFS && CONFIG_NUMA */
+
+#endif /* _LINUX_COMPACTION_H */