[PATCH v11] mm/page_alloc.c: memory_hotplug: free pages as higher order

[PATCH v11] mm/page_alloc.c: memory_hotplug: free pages as higher order

[Arun KS]

When freeing pages are done with higher order, time spent on coalescing
pages by buddy allocator can be reduced.  With section size of 256MB, hot
add latency of a single section shows improvement from 50-60 ms to less
than 1 ms, hence improving the hot add latency by 60 times.  Modify
external providers of online callback to align with the change.

Signed-off-by: Arun KS <arunks@codeaurora.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
---
Changes sinc v10:
- Fix check page belong to HAS in hv_ballon.c.
- Removed unnecessary brackets.

Changes since v9:
- Fix condition check in hv_ballon driver.

Changes since v8:
- Remove return type change for online_page_callback.
- Use consistent names for external online_page providers.
- Fix onlined_pages accounting.

Changes since v7:
- Rebased to 5.0-rc1.
- Fixed onlined_pages accounting.
- Added comment for return value of online_page_callback.
- Renamed xen_bring_pgs_online to xen_online_pages.

Changes since v6:
- Rebased to 4.20
- Changelog updated.
- No improvement seen on arm64, hence removed removal of prefetch.

Changes since v5:
- Rebased to 4.20-rc1.
- Changelog updated.

Changes since v4:
- As suggested by Michal Hocko,
- Simplify logic in online_pages_block() by using get_order().
- Seperate out removal of prefetch from __free_pages_core().

Changes since v3:
- Renamed _free_pages_boot_core -> __free_pages_core.
- Removed prefetch from __free_pages_core.
- Removed xen_online_page().

Changes since v2:
- Reuse code from __free_pages_boot_core().

Changes since v1:
- Removed prefetch().

Changes since RFC:
- Rebase.
- As suggested by Michal Hocko remove pages_per_block.
- Modifed external providers of online_page_callback.

v10: https://lore.kernel.org/patchwork/patch/1032266/
v9: https://lore.kernel.org/patchwork/patch/1030806/
v8: https://lore.kernel.org/patchwork/patch/1030332/
v7: https://lore.kernel.org/patchwork/patch/1028908/
v6: https://lore.kernel.org/patchwork/patch/1007253/
v5: https://lore.kernel.org/patchwork/patch/995739/
v4: https://lore.kernel.org/patchwork/patch/995111/
v3: https://lore.kernel.org/patchwork/patch/992348/
v2: https://lore.kernel.org/patchwork/patch/991363/
v1: https://lore.kernel.org/patchwork/patch/989445/
RFC: https://lore.kernel.org/patchwork/patch/984754/
---

 drivers/hv/hv_balloon.c        |  7 ++++---
 drivers/xen/balloon.c          | 15 ++++++++++-----
 include/linux/memory_hotplug.h |  2 +-
 mm/internal.h                  |  1 +
 mm/memory_hotplug.c            | 37 +++++++++++++++++++++++++------------
 mm/page_alloc.c                |  8 ++++----
 6 files changed, 45 insertions(+), 25 deletions(-)

diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
index 5301fef..c2cb6df 100644
--- a/drivers/hv/hv_balloon.c
+++ b/drivers/hv/hv_balloon.c
@@ -771,7 +771,7 @@ static void hv_mem_hot_add(unsigned long start, unsigned long size,
 	}
 }
 
-static void hv_online_page(struct page *pg)
+static void hv_online_page(struct page *pg, unsigned int order)
 {
 	struct hv_hotadd_state *has;
 	unsigned long flags;
@@ -780,10 +780,11 @@ static void hv_online_page(struct page *pg)
 	spin_lock_irqsave(&dm_device.ha_lock, flags);
 	list_for_each_entry(has, &dm_device.ha_region_list, list) {
 		/* The page belongs to a different HAS. */
-		if ((pfn < has->start_pfn) || (pfn >= has->end_pfn))
+		if ((pfn < has->start_pfn) ||
+				(pfn + (1UL << order) > has->end_pfn))
 			continue;
 
-		hv_page_online_one(has, pg);
+		hv_bring_pgs_online(has, pfn, 1UL << order);
 		break;
 	}
 	spin_unlock_irqrestore(&dm_device.ha_lock, flags);
diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index ceb5048..d107447 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -369,14 +369,19 @@ static enum bp_state reserve_additional_memory(void)
 	return BP_ECANCELED;
 }
 
-static void xen_online_page(struct page *page)
+static void xen_online_page(struct page *page, unsigned int order)
 {
-	__online_page_set_limits(page);
+	unsigned long i, size = (1 << order);
+	unsigned long start_pfn = page_to_pfn(page);
+	struct page *p;
 
+	pr_debug("Online %lu pages starting at pfn 0x%lx\n", size, start_pfn);
 	mutex_lock(&balloon_mutex);
-
-	__balloon_append(page);
-
+	for (i = 0; i < size; i++) {
+		p = pfn_to_page(start_pfn + i);
+		__online_page_set_limits(p);
+		__balloon_append(p);
+	}
 	mutex_unlock(&balloon_mutex);
 }
 
diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 07da5c6..e368730 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -87,7 +87,7 @@ extern int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn,
 	unsigned long *valid_start, unsigned long *valid_end);
 extern void __offline_isolated_pages(unsigned long, unsigned long);
 
-typedef void (*online_page_callback_t)(struct page *page);
+typedef void (*online_page_callback_t)(struct page *page, unsigned int order);
 
 extern int set_online_page_callback(online_page_callback_t callback);
 extern int restore_online_page_callback(online_page_callback_t callback);
diff --git a/mm/internal.h b/mm/internal.h
index f4a7bb0..536bc2a 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -163,6 +163,7 @@ static inline struct page *pageblock_pfn_to_page(unsigned long start_pfn,
 extern int __isolate_free_page(struct page *page, unsigned int order);
 extern void memblock_free_pages(struct page *page, unsigned long pfn,
 					unsigned int order);
+extern void __free_pages_core(struct page *page, unsigned int order);
 extern void prep_compound_page(struct page *page, unsigned int order);
 extern void post_alloc_hook(struct page *page, unsigned int order,
 					gfp_t gfp_flags);
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index b9a667d..77dff24 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -47,7 +47,7 @@
  * and restore_online_page_callback() for generic callback restore.
  */
 
-static void generic_online_page(struct page *page);
+static void generic_online_page(struct page *page, unsigned int order);
 
 static online_page_callback_t online_page_callback = generic_online_page;
 static DEFINE_MUTEX(online_page_callback_lock);
@@ -656,26 +656,39 @@ void __online_page_free(struct page *page)
 }
 EXPORT_SYMBOL_GPL(__online_page_free);
 
-static void generic_online_page(struct page *page)
+static void generic_online_page(struct page *page, unsigned int order)
 {
-	__online_page_set_limits(page);
-	__online_page_increment_counters(page);
-	__online_page_free(page);
+	__free_pages_core(page, order);
+	totalram_pages_add(1UL << order);
+#ifdef CONFIG_HIGHMEM
+	if (PageHighMem(page))
+		totalhigh_pages_add(1UL << order);
+#endif
+}
+
+static int online_pages_blocks(unsigned long start, unsigned long nr_pages)
+{
+	unsigned long end = start + nr_pages;
+	int order, ret, onlined_pages = 0;
+
+	while (start < end) {
+		order = min(MAX_ORDER - 1,
+			get_order(PFN_PHYS(end) - PFN_PHYS(start)));
+		(*online_page_callback)(pfn_to_page(start), order);
+
+		onlined_pages += (1UL << order);
+		start += (1UL << order);
+	}
+	return onlined_pages;
 }
 
 static int online_pages_range(unsigned long start_pfn, unsigned long nr_pages,
 			void *arg)
 {
-	unsigned long i;
 	unsigned long onlined_pages = *(unsigned long *)arg;
-	struct page *page;
 
 	if (PageReserved(pfn_to_page(start_pfn)))
-		for (i = 0; i < nr_pages; i++) {
-			page = pfn_to_page(start_pfn + i);
-			(*online_page_callback)(page);
-			onlined_pages++;
-		}
+		onlined_pages += online_pages_blocks(start_pfn, nr_pages);
 
 	online_mem_sections(start_pfn, start_pfn + nr_pages);
 
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index d295c9b..883212a 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1303,7 +1303,7 @@ static void __free_pages_ok(struct page *page, unsigned int order)
 	local_irq_restore(flags);
 }
 
-static void __init __free_pages_boot_core(struct page *page, unsigned int order)
+void __free_pages_core(struct page *page, unsigned int order)
 {
 	unsigned int nr_pages = 1 << order;
 	struct page *p = page;
@@ -1382,7 +1382,7 @@ void __init memblock_free_pages(struct page *page, unsigned long pfn,
 {
 	if (early_page_uninitialised(pfn))
 		return;
-	return __free_pages_boot_core(page, order);
+	__free_pages_core(page, order);
 }
 
 /*
@@ -1472,14 +1472,14 @@ static void __init deferred_free_range(unsigned long pfn,
 	if (nr_pages == pageblock_nr_pages &&
 	    (pfn & (pageblock_nr_pages - 1)) == 0) {
 		set_pageblock_migratetype(page, MIGRATE_MOVABLE);
-		__free_pages_boot_core(page, pageblock_order);
+		__free_pages_core(page, pageblock_order);
 		return;
 	}
 
 	for (i = 0; i < nr_pages; i++, page++, pfn++) {
 		if ((pfn & (pageblock_nr_pages - 1)) == 0)
 			set_pageblock_migratetype(page, MIGRATE_MOVABLE);
-		__free_pages_boot_core(page, 0);
+		__free_pages_core(page, 0);
 	}
 }
 
-- 
1.9.1