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Subject[RFC] memory_hotplug: Free pages as pageblock_order
Date
When free pages are done with pageblock_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%.

If this looks okey, I'll modify users of set_online_page_callback
and resend clean patch.

Signed-off-by: Arun KS <arunks@codeaurora.org>
---
include/linux/memory_hotplug.h | 1 +
mm/memory_hotplug.c | 52 ++++++++++++++++++++++++++++++++++++------
2 files changed, 46 insertions(+), 7 deletions(-)

diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 34a2822..447047d 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -88,6 +88,7 @@ extern int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn,
extern void __offline_isolated_pages(unsigned long, unsigned long);

typedef void (*online_page_callback_t)(struct page *page);
+typedef int (*online_pages_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..853104d 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -662,19 +662,57 @@ static void generic_online_page(struct page *page)
__online_page_free(page);
}

+static int generic_online_pages(struct page *page, unsigned int order);
+static online_pages_callback_t online_pages_callback = generic_online_pages;
+
+static int generic_online_pages(struct page *page, unsigned int order)
+{
+ unsigned long nr_pages = 1 << order;
+ struct page *p = page;
+ unsigned int loop;
+
+ for (loop = 0 ; loop < nr_pages ; loop++, p++) {
+ __ClearPageReserved(p);
+ set_page_count(p, 0);
+ }
+ adjust_managed_page_count(page, nr_pages);
+ init_page_count(page);
+ __free_pages(page, order);
+
+ return 0;
+}
+
+static int online_pages_blocks(unsigned long start_pfn, unsigned long nr_pages)
+{
+ unsigned long pages_per_block = (1 << pageblock_order);
+ unsigned long nr_pageblocks = nr_pages / pages_per_block;
+// unsigned long rem_pages = nr_pages % pages_per_block;
+ int i, ret, onlined_pages = 0;
+ struct page *page;
+
+ for (i = 0 ; i < nr_pageblocks ; i++) {
+ page = pfn_to_page(start_pfn + (i * pages_per_block));
+ ret = (*online_pages_callback)(page, pageblock_order);
+ if (!ret)
+ onlined_pages += pages_per_block;
+ else if (ret > 0)
+ onlined_pages += ret;
+ }
+/*
+ if (rem_pages)
+ onlined_pages += online_page_single(start_pfn + i, rem_pages);
+*/
+
+ 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
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