Andrew Morton pointed out that page_xchg_last_nid() and reset_page_last_nid()
were "getting nuttily large" and asked that it be investigated.
reset_page_last_nid() is on the page free path and it would be unfortunate
to make that path more expensive than it needs to be. Due to the internal
use of page_xchg_last_nid() it is already too expensive but fortunately,
it should also be impossible for the page->flags to be updated in parallel
when we call reset_page_last_nid(). Instead of unlining the function,
it uses a simplier implementation that assumes no parallel updates and
should now be sufficiently short for inlining.
page_xchg_last_nid() is called in paths that are already quite expensive
(splitting huge page, fault handling, migration) and it is reasonable to
uninline. There was not really a good place to place the function but
mm/mmzone.c was the closest fit IMO.
This patch saved 128 bytes of text in the vmlinux file for the kernel
configuration I used for testing automatic NUMA balancing.
Signed-off-by: Mel Gorman <mgor...@suse.de>
---
include/linux/mm.h | 21 +++++----------------
mm/mmzone.c | 20 +++++++++++++++++++-
2 files changed, 24 insertions(+), 17 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index e25d47f..6e4468f 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -676,25 +676,14 @@ static inline int page_last_nid(struct page *page)
return (page->flags >> LAST_NID_PGSHIFT) & LAST_NID_MASK;
}
-static inline int page_xchg_last_nid(struct page *page, int nid)
-{
- unsigned long old_flags, flags;
- int last_nid;
-
- do {
- old_flags = flags = page->flags;
- last_nid = page_last_nid(page);
-
- flags &= ~(LAST_NID_MASK << LAST_NID_PGSHIFT);
- flags |= (nid & LAST_NID_MASK) << LAST_NID_PGSHIFT;
- } while (unlikely(cmpxchg(&page->flags, old_flags, flags) !=
old_flags));
-
- return last_nid;
-}
+extern int page_xchg_last_nid(struct page *page, int nid);
static inline void reset_page_last_nid(struct page *page)
{
- page_xchg_last_nid(page, (1 << LAST_NID_SHIFT) - 1);
+ int nid = (1 << LAST_NID_SHIFT) - 1;
+
+ page->flags &= ~(LAST_NID_MASK << LAST_NID_PGSHIFT);
+ page->flags |= (nid & LAST_NID_MASK) << LAST_NID_PGSHIFT;
}
#endif /* LAST_NID_NOT_IN_PAGE_FLAGS */
#else
diff --git a/mm/mmzone.c b/mm/mmzone.c
index 4596d81..bce796e 100644
--- a/mm/mmzone.c
+++ b/mm/mmzone.c
@@ -1,7 +1,7 @@
/*
* linux/mm/mmzone.c
*
- * management codes for pgdats and zones.
+ * management codes for pgdats, zones and page flags
*/
@@ -96,3 +96,21 @@ void lruvec_init(struct lruvec *lruvec)
for_each_lru(lru)
INIT_LIST_HEAD(&lruvec->lists[lru]);
}
+
+#if defined(CONFIG_NUMA_BALANCING) && !defined(LAST_NID_NOT_IN_PAGE_FLAGS)
+int page_xchg_last_nid(struct page *page, int nid)
+{
+ unsigned long old_flags, flags;
+ int last_nid;
+
+ do {
+ old_flags = flags = page->flags;
+ last_nid = page_last_nid(page);
+
+ flags &= ~(LAST_NID_MASK << LAST_NID_PGSHIFT);
+ flags |= (nid & LAST_NID_MASK) << LAST_NID_PGSHIFT;
+ } while (unlikely(cmpxchg(&page->flags, old_flags, flags) !=
old_flags));
+
+ return last_nid;
+}
+#endif
--
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