[PATCH 08/13] mm: meminit: Initialise remaining struct pages in parallel with kswapd

[Mel Gorman]

Only a subset of struct pages are initialised at the moment. When this patch
is applied kswapd initialise the remaining struct pages in parallel. This
should boot faster by spreading the work to multiple CPUs and initialising
data that is local to the CPU.  The user-visible effect on large machines
is that free memory will appear to rapidly increase early in the lifetime
of the system until kswapd reports that all memory is initialised in the
kernel log.  Once initialised there should be no other user-visibile effects.

Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
---
 mm/internal.h   |   6 +++
 mm/mm_init.c    |   1 +
 mm/page_alloc.c | 116 ++++++++++++++++++++++++++++++++++++++++++++++++++++++--
 mm/vmscan.c     |   6 ++-
 4 files changed, 123 insertions(+), 6 deletions(-)

diff --git a/mm/internal.h b/mm/internal.h
index 4a73f74846bd..2c4057140bec 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -388,9 +388,15 @@ static inline void mminit_verify_zonelist(void)
 #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
 #define __defermem_init __meminit
 #define __defer_init    __meminit
+
+void deferred_init_memmap(int nid);
 #else
 #define __defermem_init
 #define __defer_init __init
+
+static inline void deferred_init_memmap(int nid)
+{
+}
 #endif
 
 /* mminit_validate_memmodel_limits is independent of CONFIG_DEBUG_MEMORY_INIT */
diff --git a/mm/mm_init.c b/mm/mm_init.c
index 5f420f7fafa1..28fbf87b20aa 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -11,6 +11,7 @@
 #include <linux/export.h>
 #include <linux/memory.h>
 #include <linux/notifier.h>
+#include <linux/sched.h>
 #include "internal.h"
 
 #ifdef CONFIG_DEBUG_MEMORY_INIT
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 2d649e0a1f9e..dfe63a3c3816 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -252,6 +252,14 @@ static inline bool __defermem_init early_page_uninitialised(unsigned long pfn)
 	return false;
 }
 
+static inline bool early_page_nid_uninitialised(unsigned long pfn, int nid)
+{
+	if (pfn >= NODE_DATA(nid)->first_deferred_pfn)
+		return true;
+
+	return false;
+}
+
 /*
  * Returns false when the remaining initialisation should be deferred until
  * later in the boot cycle when it can be parallelised.
@@ -287,6 +295,11 @@ static inline bool early_page_uninitialised(unsigned long pfn)
 	return false;
 }
 
+static inline bool early_page_nid_uninitialised(unsigned long pfn, int nid)
+{
+	return false;
+}
+
 static inline bool update_defer_init(pg_data_t *pgdat,
 				unsigned long pfn, unsigned long zone_end,
 				unsigned long *nr_initialised)
@@ -883,14 +896,45 @@ static void __meminit __init_single_pfn(unsigned long pfn, unsigned long zone,
 	return __init_single_page(pfn_to_page(pfn), pfn, zone, nid);
 }
 
-void reserve_bootmem_region(unsigned long start, unsigned long end)
+#ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
+static void init_reserved_page(unsigned long pfn)
+{
+	pg_data_t *pgdat;
+	int nid, zid;
+
+	if (!early_page_uninitialised(pfn))
+		return;
+
+	nid = early_pfn_to_nid(pfn);
+	pgdat = NODE_DATA(nid);
+
+	for (zid = 0; zid < MAX_NR_ZONES; zid++) {
+		struct zone *zone = &pgdat->node_zones[zid];
+
+		if (pfn >= zone->zone_start_pfn && pfn < zone_end_pfn(zone))
+			break;
+	}
+	__init_single_pfn(pfn, zid, nid);
+}
+#else
+static inline void init_reserved_page(unsigned long pfn)
+{
+}
+#endif /* CONFIG_DEFERRED_STRUCT_PAGE_INIT */
+
+void __meminit reserve_bootmem_region(unsigned long start, unsigned long end)
 {
 	unsigned long start_pfn = PFN_DOWN(start);
 	unsigned long end_pfn = PFN_UP(end);
 
-	for (; start_pfn < end_pfn; start_pfn++)
-		if (pfn_valid(start_pfn))
-			SetPageReserved(pfn_to_page(start_pfn));
+	for (; start_pfn < end_pfn; start_pfn++) {
+		if (pfn_valid(start_pfn)) {
+			struct page *page = pfn_to_page(start_pfn);
+
+			init_reserved_page(start_pfn);
+			SetPageReserved(page);
+		}
+	}
 }
 
 static bool free_pages_prepare(struct page *page, unsigned int order)
@@ -1019,6 +1063,67 @@ void __defer_init __free_pages_bootmem(struct page *page, unsigned long pfn,
 	return __free_pages_boot_core(page, pfn, order);
 }
 
+#ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
+/* Initialise remaining memory on a node */
+void __defermem_init deferred_init_memmap(int nid)
+{
+	unsigned long start = jiffies;
+	struct mminit_pfnnid_cache nid_init_state = { };
+
+	pg_data_t *pgdat = NODE_DATA(nid);
+	int zid;
+	unsigned long first_init_pfn = pgdat->first_deferred_pfn;
+
+	if (first_init_pfn == ULONG_MAX)
+		return;
+
+	/* Sanity check boundaries */
+	BUG_ON(pgdat->first_deferred_pfn < pgdat->node_start_pfn);
+	BUG_ON(pgdat->first_deferred_pfn > pgdat_end_pfn(pgdat));
+	pgdat->first_deferred_pfn = ULONG_MAX;
+
+	for (zid = 0; zid < MAX_NR_ZONES; zid++) {
+		struct zone *zone = pgdat->node_zones + zid;
+		unsigned long walk_start, walk_end;
+		int i;
+
+		for_each_mem_pfn_range(i, nid, &walk_start, &walk_end, NULL) {
+			unsigned long pfn, end_pfn;
+
+			end_pfn = min(walk_end, zone_end_pfn(zone));
+			pfn = first_init_pfn;
+			if (pfn < walk_start)
+				pfn = walk_start;
+			if (pfn < zone->zone_start_pfn)
+				pfn = zone->zone_start_pfn;
+
+			for (; pfn < end_pfn; pfn++) {
+				struct page *page;
+
+				if (!pfn_valid(pfn))
+					continue;
+
+				if (!meminit_pfn_in_nid(pfn, nid, &nid_init_state))
+					continue;
+
+				if (page->flags) {
+					VM_BUG_ON(page_zone(page) != zone);
+					continue;
+				}
+
+				__init_single_page(page, pfn, zid, nid);
+				__free_pages_boot_core(page, pfn, 0);
+				cond_resched();
+			}
+			first_init_pfn = max(end_pfn, first_init_pfn);
+		}
+	}
+
+	pr_info("kswapd %d initialised deferred memory in %ums\n", nid,
+					jiffies_to_msecs(jiffies - start));
+}
+#endif /* CONFIG_DEFERRED_STRUCT_PAGE_INIT */
+
 #ifdef CONFIG_CMA
 /* Free whole pageblock and set its migration type to MIGRATE_CMA. */
 void __init init_cma_reserved_pageblock(struct page *page)
@@ -4229,6 +4334,9 @@ static void setup_zone_migrate_reserve(struct zone *zone)
 	zone->nr_migrate_reserve_block = reserve;
 
 	for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
+		if (!early_page_nid_uninitialised(pfn, zone_to_nid(zone)))
+			return;
+
 		if (!pfn_valid(pfn))
 			continue;
 		page = pfn_to_page(pfn);
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 5e8eadd71bac..c4895d26d036 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3348,7 +3348,7 @@ static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx)
  * If there are applications that are active memory-allocators
  * (most normal use), this basically shouldn't matter.
  */
-static int kswapd(void *p)
+static int __defermem_init kswapd(void *p)
 {
 	unsigned long order, new_order;
 	unsigned balanced_order;
@@ -3383,6 +3383,8 @@ static int kswapd(void *p)
 	tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
 	set_freezable();
 
+	deferred_init_memmap(pgdat->node_id);
+
 	order = new_order = 0;
 	balanced_order = 0;
 	classzone_idx = new_classzone_idx = pgdat->nr_zones - 1;
@@ -3538,7 +3540,7 @@ static int cpu_callback(struct notifier_block *nfb, unsigned long action,
  * This kswapd start function will be called by init and node-hot-add.
  * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
  */
-int kswapd_run(int nid)
+int __defermem_init kswapd_run(int nid)
 {
 	pg_data_t *pgdat = NODE_DATA(nid);
 	int ret = 0;
-- 
2.1.2

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