The patch titled
Subject: mm-free_pcppages_bulk-prefetch-buddy-while-not-holding-lock-v4-update2
has been added to the -mm tree. Its filename is
mm-free_pcppages_bulk-prefetch-buddy-while-not-holding-lock-v4-update2.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-free_pcppages_bulk-prefetch-buddy-while-not-holding-lock-v4-update2.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-free_pcppages_bulk-prefetch-buddy-while-not-holding-lock-v4-update2.patch
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------------------------------------------------------
From: Aaron Lu <aaron.lu@xxxxxxxxx>
Subject: mm-free_pcppages_bulk-prefetch-buddy-while-not-holding-lock-v4-update2
Use a helper function to prefetch buddy as suggested by Dave Hansen.
Drop the change of list_add_tail() to avoid disordering page.
Link: http://lkml.kernel.org/r/20180301062845.26038-4-aaron.lu@xxxxxxxxx
Link: http://lkml.kernel.org/r/20180320113146.GB24737@xxxxxxxxx
Signed-off-by: Aaron Lu <aaron.lu@xxxxxxxxx>
Suggested-by: Ying Huang <ying.huang@xxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
diff -puN mm/page_alloc.c~mm-free_pcppages_bulk-prefetch-buddy-while-not-holding-lock-v4-update2 mm/page_alloc.c
--- a/mm/page_alloc.c~mm-free_pcppages_bulk-prefetch-buddy-while-not-holding-lock-v4-update2
+++ a/mm/page_alloc.c
@@ -1063,6 +1063,15 @@ static bool bulkfree_pcp_prepare(struct
}
#endif /* CONFIG_DEBUG_VM */
+static inline void prefetch_buddy(struct page *page)
+{
+ unsigned long pfn = page_to_pfn(page);
+ unsigned long buddy_pfn = __find_buddy_pfn(pfn, 0);
+ struct page *buddy = page + (buddy_pfn - pfn);
+
+ prefetch(buddy);
+}
+
/*
* Frees a number of pages from the PCP lists
* Assumes all pages on list are in same zone, and of same order.
@@ -1079,6 +1088,7 @@ static void free_pcppages_bulk(struct zo
{
int migratetype = 0;
int batch_free = 0;
+ int prefetch_nr = 0;
bool isolated_pageblocks;
struct page *page, *tmp;
LIST_HEAD(head);
@@ -1105,9 +1115,6 @@ static void free_pcppages_bulk(struct zo
batch_free = count;
do {
- unsigned long pfn, buddy_pfn;
- struct page *buddy;
-
page = list_last_entry(list, struct page, lru);
/* must delete to avoid corrupting pcp list */
list_del(&page->lru);
@@ -1116,7 +1123,7 @@ static void free_pcppages_bulk(struct zo
if (bulkfree_pcp_prepare(page))
continue;
- list_add(&page->lru, &head);
+ list_add_tail(&page->lru, &head);
/*
* We are going to put the page back to the global
@@ -1125,14 +1132,10 @@ static void free_pcppages_bulk(struct zo
* an additional test and calculating buddy_pfn here
* can be offset by reduced memory latency later. To
* avoid excessive prefetching due to large count, only
- * prefetch buddy for the last pcp->batch nr of pages.
+ * prefetch buddy for the first pcp->batch nr of pages.
*/
- if (count > pcp->batch)
- continue;
- pfn = page_to_pfn(page);
- buddy_pfn = __find_buddy_pfn(pfn, 0);
- buddy = page + (buddy_pfn - pfn);
- prefetch(buddy);
+ if (prefetch_nr++ < pcp->batch)
+ prefetch_buddy(page);
} while (--count && --batch_free && !list_empty(list));
}
_
Patches currently in -mm which might be from aaron.lu@xxxxxxxxx are
mm-free_pcppages_bulk-update-pcp-count-inside.patch
mm-free_pcppages_bulk-do-not-hold-lock-when-picking-pages-to-free.patch
mm-free_pcppages_bulk-prefetch-buddy-while-not-holding-lock.patch
mm-free_pcppages_bulk-prefetch-buddy-while-not-holding-lock-v4-update2.patch
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