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Subject[PATCH 12/52] mm/migrate: Introduce migrate_misplaced_page()
Date
From: Peter Zijlstra <a.p.zijlstra@chello.nl>

Note: This was originally based on Peter's patch "mm/migrate:
Introduce migrate_misplaced_page()" but borrows extremely heavily from Andrea's
"autonuma: memory follows CPU algorithm and task/mm_autonuma stats
collection". The end result is barely recognisable so signed-offs
had to be dropped. If original authors are ok with it, I'll
re-add the signed-off-bys.

Add migrate_misplaced_page() which deals with migrating pages
from faults.

Based-on-work-by: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
Based-on-work-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Based-on-work-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Paul Turner <pjt@google.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
Cc: Alex Shi <lkml.alex@gmail.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Aneesh Kumar <aneesh.kumar@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
include/linux/migrate.h | 16 +++++++
mm/migrate.c | 108 +++++++++++++++++++++++++++++++++++++++++++++++-
2 files changed, 122 insertions(+), 2 deletions(-)

diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index 9d1c159..f7404b6 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -13,6 +13,7 @@ enum migrate_reason {
MR_MEMORY_HOTPLUG,
MR_SYSCALL, /* also applies to cpusets */
MR_MEMPOLICY_MBIND,
+ MR_NUMA_MISPLACED,
MR_CMA
};

@@ -39,6 +40,15 @@ extern int migrate_vmas(struct mm_struct *mm,
extern void migrate_page_copy(struct page *newpage, struct page *page);
extern int migrate_huge_page_move_mapping(struct address_space *mapping,
struct page *newpage, struct page *page);
+#ifdef CONFIG_NUMA_BALANCING
+extern int migrate_misplaced_page(struct page *page, int node);
+#else
+static inline
+int migrate_misplaced_page(struct page *page, int node)
+{
+ return -EAGAIN; /* can't migrate now */
+}
+#endif
#else

static inline void putback_lru_pages(struct list_head *l) {}
@@ -72,5 +82,11 @@ static inline int migrate_huge_page_move_mapping(struct address_space *mapping,
#define migrate_page NULL
#define fail_migrate_page NULL

+static inline
+int migrate_misplaced_page(struct page *page, int node)
+{
+ return -EAGAIN; /* can't migrate now */
+}
#endif /* CONFIG_MIGRATION */
+
#endif /* _LINUX_MIGRATE_H */
diff --git a/mm/migrate.c b/mm/migrate.c
index 27be9c9..d168aec 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -282,7 +282,7 @@ static int migrate_page_move_mapping(struct address_space *mapping,
struct page *newpage, struct page *page,
struct buffer_head *head, enum migrate_mode mode)
{
- int expected_count;
+ int expected_count = 0;
void **pslot;

if (!mapping) {
@@ -1415,4 +1415,108 @@ int migrate_vmas(struct mm_struct *mm, const nodemask_t *to,
}
return err;
}
-#endif
+
+#ifdef CONFIG_NUMA_BALANCING
+/*
+ * Returns true if this is a safe migration target node for misplaced NUMA
+ * pages. Currently it only checks the watermarks which crude
+ */
+static bool migrate_balanced_pgdat(struct pglist_data *pgdat,
+ int nr_migrate_pages)
+{
+ int z;
+ for (z = pgdat->nr_zones - 1; z >= 0; z--) {
+ struct zone *zone = pgdat->node_zones + z;
+
+ if (!populated_zone(zone))
+ continue;
+
+ if (zone->all_unreclaimable)
+ continue;
+
+ /* Avoid waking kswapd by allocating pages_to_migrate pages. */
+ if (!zone_watermark_ok(zone, 0,
+ high_wmark_pages(zone) +
+ nr_migrate_pages,
+ 0, 0))
+ continue;
+ return true;
+ }
+ return false;
+}
+
+static struct page *alloc_misplaced_dst_page(struct page *page,
+ unsigned long data,
+ int **result)
+{
+ int nid = (int) data;
+ struct page *newpage;
+
+ newpage = alloc_pages_exact_node(nid,
+ (GFP_HIGHUSER_MOVABLE | GFP_THISNODE |
+ __GFP_NOMEMALLOC | __GFP_NORETRY |
+ __GFP_NOWARN) &
+ ~GFP_IOFS, 0);
+ return newpage;
+}
+
+/*
+ * Attempt to migrate a misplaced page to the specified destination
+ * node. Caller is expected to have an elevated reference count on
+ * the page that will be dropped by this function before returning.
+ */
+int migrate_misplaced_page(struct page *page, int node)
+{
+ int isolated = 0;
+ LIST_HEAD(migratepages);
+
+ /*
+ * Don't migrate pages that are mapped in multiple processes.
+ * TODO: Handle false sharing detection instead of this hammer
+ */
+ if (page_mapcount(page) != 1) {
+ put_page(page);
+ goto out;
+ }
+
+ /* Avoid migrating to a node that is nearly full */
+ if (migrate_balanced_pgdat(NODE_DATA(node), 1)) {
+ int page_lru;
+
+ if (isolate_lru_page(page)) {
+ put_page(page);
+ goto out;
+ }
+ isolated = 1;
+
+ /*
+ * Page is isolated which takes a reference count so now the
+ * callers reference can be safely dropped without the page
+ * disappearing underneath us during migration
+ */
+ put_page(page);
+
+ page_lru = page_is_file_cache(page);
+ inc_zone_page_state(page, NR_ISOLATED_ANON + page_lru);
+ list_add(&page->lru, &migratepages);
+ }
+
+ if (isolated) {
+ int nr_remaining;
+
+ nr_remaining = migrate_pages(&migratepages,
+ alloc_misplaced_dst_page,
+ node, false, MIGRATE_ASYNC,
+ MR_NUMA_MISPLACED);
+ if (nr_remaining) {
+ putback_lru_pages(&migratepages);
+ isolated = 0;
+ }
+ }
+ BUG_ON(!list_empty(&migratepages));
+out:
+ return isolated;
+}
+#endif /* CONFIG_NUMA_BALANCING */
+
+#endif /* CONFIG_NUMA */
--
1.7.11.7


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