[PATCH] memory_hotplug: Free pages as higher order
From: Arun KS
Date: Fri Sep 21 2018 - 05:38:52 EST
When free pages are done with higher order, time spend 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%.
Modify external providers of online callback to align with
the change.
Signed-off-by: Arun KS <arunks@xxxxxxxxxxxxxx>
---
Changes since RFC:
- Rebase.
- As suggested by Michal Hocko remove pages_per_block.
- Modifed external providers of online_page_callback.
RFC:
https://lore.kernel.org/patchwork/patch/984754/
---
drivers/hv/hv_balloon.c | 6 +++--
drivers/xen/balloon.c | 18 +++++++++++---
include/linux/memory_hotplug.h | 2 +-
mm/memory_hotplug.c | 55 +++++++++++++++++++++++++++++++++---------
4 files changed, 63 insertions(+), 18 deletions(-)
diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
index b1b7880..c5bc0b5 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 int hv_online_page(struct page *pg, unsigned int order)
{
struct hv_hotadd_state *has;
unsigned long flags;
@@ -783,10 +783,12 @@ static void hv_online_page(struct page *pg)
if ((pfn < has->start_pfn) || (pfn >= 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);
+
+ return 0;
}
static int pfn_covered(unsigned long start_pfn, unsigned long pfn_cnt)
diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index e12bb25..010cf4d 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -390,8 +390,8 @@ static enum bp_state reserve_additional_memory(void)
/*
* add_memory_resource() will call online_pages() which in its turn
- * will call xen_online_page() callback causing deadlock if we don't
- * release balloon_mutex here. Unlocking here is safe because the
+ * will call xen_bring_pgs_online() callback causing deadlock if we
+ * don't release balloon_mutex here. Unlocking here is safe because the
* callers drop the mutex before trying again.
*/
mutex_unlock(&balloon_mutex);
@@ -422,6 +422,18 @@ static void xen_online_page(struct page *page)
mutex_unlock(&balloon_mutex);
}
+static int xen_bring_pgs_online(struct page *pg, unsigned int order)
+{
+ unsigned long i, size = (1 << order);
+ unsigned long start_pfn = page_to_pfn(pg);
+
+ pr_debug("Online %lu pages starting at pfn 0x%lx\n", size, start_pfn);
+ for (i = 0; i < size; i++)
+ xen_online_page(pfn_to_page(start_pfn + i));
+
+ return 0;
+}
+
static int xen_memory_notifier(struct notifier_block *nb, unsigned long val, void *v)
{
if (val == MEM_ONLINE)
@@ -744,7 +756,7 @@ static int __init balloon_init(void)
balloon_stats.max_retry_count = RETRY_UNLIMITED;
#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
- set_online_page_callback(&xen_online_page);
+ set_online_page_callback(&xen_bring_pgs_online);
register_memory_notifier(&xen_memory_nb);
register_sysctl_table(xen_root);
diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 34a2822..7b04c1d 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 int (*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/memory_hotplug.c b/mm/memory_hotplug.c
index 38d94b7..24c2b8e 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 int 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);
@@ -655,26 +655,57 @@ void __online_page_free(struct page *page)
}
EXPORT_SYMBOL_GPL(__online_page_free);
-static void generic_online_page(struct page *page)
+static int generic_online_page(struct page *page, unsigned int order)
{
- __online_page_set_limits(page);
- __online_page_increment_counters(page);
- __online_page_free(page);
+ unsigned long nr_pages = 1 << order;
+ struct page *p = page;
+ unsigned int loop;
+
+ prefetchw(p);
+ for (loop = 0 ; loop < (nr_pages - 1) ; loop++, p++) {
+ prefetch(p + 1);
+ __ClearPageReserved(p);
+ set_page_count(p, 0);
+ }
+ __ClearPageReserved(p);
+ set_page_count(p, 0);
+
+ adjust_managed_page_count(page, nr_pages);
+ set_page_refcounted(page);
+ __free_pages(page, order);
+
+ return 0;
+}
+
+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 - 1UL, __ffs(start));
+
+ while (start + (1UL << order) > end)
+ order--;
+
+ ret = (*online_page_callback)(pfn_to_page(start), order);
+ if (!ret)
+ onlined_pages += (1UL << order);
+ else if (ret > 0)
+ onlined_pages += ret;
+
+ 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);
--
1.9.1