lkml.org 
[lkml]   [2012]   [Nov]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 14/33] mm/migration: Improve migrate_misplaced_page()
Date
From: Mel Gorman <mgorman@suse.de>

Fix, improve and clean up migrate_misplaced_page() to
reuse migrate_pages() and to check for zone watermarks
to make sure we don't overload the node.

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".

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: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Linux-MM <linux-mm@kvack.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Link: http://lkml.kernel.org/r/1353064973-26082-14-git-send-email-mgorman@suse.de
[ Adapted to the numa/core tree. Kept Mel's patch separate to retain
original authorship for the authors. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
include/linux/migrate_mode.h | 3 -
mm/memory.c | 13 ++--
mm/migrate.c | 143 +++++++++++++++++++++++++++----------------
3 files changed, 95 insertions(+), 64 deletions(-)

diff --git a/include/linux/migrate_mode.h b/include/linux/migrate_mode.h
index 40b37dc..ebf3d89 100644
--- a/include/linux/migrate_mode.h
+++ b/include/linux/migrate_mode.h
@@ -6,14 +6,11 @@
* on most operations but not ->writepage as the potential stall time
* is too significant
* MIGRATE_SYNC will block when migrating pages
- * MIGRATE_FAULT called from the fault path to migrate-on-fault for mempolicy
- * this path has an extra reference count
*/
enum migrate_mode {
MIGRATE_ASYNC,
MIGRATE_SYNC_LIGHT,
MIGRATE_SYNC,
- MIGRATE_FAULT,
};

#endif /* MIGRATE_MODE_H_INCLUDED */
diff --git a/mm/memory.c b/mm/memory.c
index 23ad2eb..52ad29d 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3492,28 +3492,25 @@ out_pte_upgrade_unlock:

out_unlock:
pte_unmap_unlock(ptep, ptl);
-out:
+
if (page) {
task_numa_fault(page_nid, last_cpu, 1);
put_page(page);
}
-
+out:
return 0;

migrate:
pte_unmap_unlock(ptep, ptl);

- if (!migrate_misplaced_page(page, node)) {
- page_nid = node;
+ if (migrate_misplaced_page(page, node)) {
goto out;
}
+ page = NULL;

ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
- if (!pte_same(*ptep, entry)) {
- put_page(page);
- page = NULL;
+ if (!pte_same(*ptep, entry))
goto out_unlock;
- }

goto out_pte_upgrade_unlock;
}
diff --git a/mm/migrate.c b/mm/migrate.c
index b89062d..16a4709 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -225,7 +225,7 @@ static bool buffer_migrate_lock_buffers(struct buffer_head *head,
struct buffer_head *bh = head;

/* Simple case, sync compaction */
- if (mode != MIGRATE_ASYNC && mode != MIGRATE_FAULT) {
+ if (mode != MIGRATE_ASYNC) {
do {
get_bh(bh);
lock_buffer(bh);
@@ -282,19 +282,9 @@ static int migrate_page_move_mapping(struct address_space *mapping,
int expected_count = 0;
void **pslot;

- if (mode == MIGRATE_FAULT) {
- /*
- * MIGRATE_FAULT has an extra reference on the page and
- * otherwise acts like ASYNC, no point in delaying the
- * fault, we'll try again next time.
- */
- expected_count++;
- }
-
if (!mapping) {
/* Anonymous page without mapping */
- expected_count += 1;
- if (page_count(page) != expected_count)
+ if (page_count(page) != 1)
return -EAGAIN;
return 0;
}
@@ -304,7 +294,7 @@ static int migrate_page_move_mapping(struct address_space *mapping,
pslot = radix_tree_lookup_slot(&mapping->page_tree,
page_index(page));

- expected_count += 2 + page_has_private(page);
+ expected_count = 2 + page_has_private(page);
if (page_count(page) != expected_count ||
radix_tree_deref_slot_protected(pslot, &mapping->tree_lock) != page) {
spin_unlock_irq(&mapping->tree_lock);
@@ -323,7 +313,7 @@ static int migrate_page_move_mapping(struct address_space *mapping,
* the mapping back due to an elevated page count, we would have to
* block waiting on other references to be dropped.
*/
- if ((mode == MIGRATE_ASYNC || mode == MIGRATE_FAULT) && head &&
+ if (mode == MIGRATE_ASYNC && head &&
!buffer_migrate_lock_buffers(head, mode)) {
page_unfreeze_refs(page, expected_count);
spin_unlock_irq(&mapping->tree_lock);
@@ -531,7 +521,7 @@ int buffer_migrate_page(struct address_space *mapping,
* with an IRQ-safe spinlock held. In the sync case, the buffers
* need to be locked now
*/
- if (mode != MIGRATE_ASYNC && mode != MIGRATE_FAULT)
+ if (mode != MIGRATE_ASYNC)
BUG_ON(!buffer_migrate_lock_buffers(head, mode));

ClearPagePrivate(page);
@@ -697,7 +687,7 @@ static int __unmap_and_move(struct page *page, struct page *newpage,
struct anon_vma *anon_vma = NULL;

if (!trylock_page(page)) {
- if (!force || mode == MIGRATE_ASYNC || mode == MIGRATE_FAULT)
+ if (!force || mode == MIGRATE_ASYNC)
goto out;

/*
@@ -1415,55 +1405,102 @@ int migrate_vmas(struct mm_struct *mm, const nodemask_t *to,
}

/*
+ * Returns true if this is a safe migration target node for misplaced NUMA
+ * pages. Currently it only checks the watermarks which is a bit 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.
+ * 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)
{
- struct address_space *mapping = page_mapping(page);
- int page_lru = page_is_file_cache(page);
- struct page *newpage;
- int ret = -EAGAIN;
- gfp_t gfp = GFP_HIGHUSER_MOVABLE;
+ int isolated = 0;
+ LIST_HEAD(migratepages);

/*
- * Never wait for allocations just to migrate on fault, but don't dip
- * into reserves. And, only accept pages from the specified node. No
- * sense migrating to a different "misplaced" page!
+ * Don't migrate pages that are mapped in multiple processes.
+ * TODO: Handle false sharing detection instead of this hammer
*/
- if (mapping)
- gfp = mapping_gfp_mask(mapping);
- gfp &= ~__GFP_WAIT;
- gfp |= __GFP_NOMEMALLOC | GFP_THISNODE;
-
- newpage = alloc_pages_node(node, gfp, 0);
- if (!newpage) {
- ret = -ENOMEM;
+ if (page_mapcount(page) != 1)
goto out;
- }

- if (isolate_lru_page(page)) {
- ret = -EBUSY;
- goto put_new;
+ /* 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);
}

- inc_zone_page_state(page, NR_ISOLATED_ANON + page_lru);
- ret = __unmap_and_move(page, newpage, 0, 0, MIGRATE_FAULT);
- /*
- * A page that has been migrated has all references removed and will be
- * freed. A page that has not been migrated will have kepts its
- * references and be restored.
- */
- dec_zone_page_state(page, NR_ISOLATED_ANON + page_lru);
- putback_lru_page(page);
-put_new:
- /*
- * Move the new page to the LRU. If migration was not successful
- * then this will free the page.
- */
- putback_lru_page(newpage);
+ if (isolated) {
+ int nr_remaining;
+
+ nr_remaining = migrate_pages(&migratepages,
+ alloc_misplaced_dst_page,
+ node, false, MIGRATE_ASYNC);
+ if (nr_remaining) {
+ putback_lru_pages(&migratepages);
+ isolated = 0;
+ }
+ }
+ BUG_ON(!list_empty(&migratepages));
out:
- return ret;
+ return isolated;
}

#endif /* CONFIG_NUMA */
--
1.7.11.7


\
 
 \ /
  Last update: 2012-11-23 03:01    [W:0.249 / U:14.832 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site