Re: [PATCH] mm, compaction: fix NR_ISOLATED_* stats for pfn based migration
From: Vlastimil Babka
Date: Wed Oct 19 2016 - 11:13:59 EST
On 10/19/2016 10:02 AM, Michal Hocko wrote:
From: Ming Ling <ming.ling@xxxxxxxxxxxxxx>
Since bda807d44454 ("mm: migrate: support non-lru movable page
migration") isolate_migratepages_block) can isolate !PageLRU pages which
would acct_isolated account as NR_ISOLATED_*. Accounting these non-lru
pages NR_ISOLATED_{ANON,FILE} doesn't make any sense and it can misguide
heuristics based on those counters such as pgdat_reclaimable_pages resp.
too_many_isolated which would lead to unexpected stalls during the
direct reclaim without any good reason. Note that
__alloc_contig_migrate_range can isolate a lot of pages at once.
On mobile devices such as 512M ram android Phone, it may use a big zram
swap. In some cases zram(zsmalloc) uses too many non-lru but migratedable
pages, such as:
MemTotal: 468148 kB
Normal free:5620kB
Free swap:4736kB
Total swap:409596kB
ZRAM: 164616kB(zsmalloc non-lru pages)
active_anon:60700kB
inactive_anon:60744kB
active_file:34420kB
inactive_file:37532kB
Fix this by only accounting lru pages to NR_ISOLATED_* in
isolate_migratepages_block right after they were isolated and we still
know they were on LRU. Drop acct_isolated because it is called after the
fact and we've lost that information. Batching per-cpu counter doesn't
make much improvement anyway. Also make sure that we uncharge only LRU
pages when putting them back on the LRU in putback_movable_pages resp.
when unmap_and_move migrates the page.
[mhocko@xxxxxxxx: replace acct_isolated() with direct counting]
?
Indeed much better than before. IIRC I've personally introduced one or two bugs
involving acct_isolated() (lack of) usage :) Thanks.
Fixes: bda807d44454 ("mm: migrate: support non-lru movable page migration")
Acked-by: Minchan Kim <minchan@xxxxxxxxxx>
Signed-off-by: Ming Ling <ming.ling@xxxxxxxxxxxxxx>
Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
---
mm/compaction.c | 25 +++----------------------
mm/migrate.c | 15 +++++++++++----
2 files changed, 14 insertions(+), 26 deletions(-)
diff --git a/mm/compaction.c b/mm/compaction.c
index 0409a4ad6ea1..70e6bec46dc2 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -634,22 +634,6 @@ isolate_freepages_range(struct compact_control *cc,
return pfn;
}
-/* Update the number of anon and file isolated pages in the zone */
-static void acct_isolated(struct zone *zone, struct compact_control *cc)
-{
- struct page *page;
- unsigned int count[2] = { 0, };
-
- if (list_empty(&cc->migratepages))
- return;
-
- list_for_each_entry(page, &cc->migratepages, lru)
- count[!!page_is_file_cache(page)]++;
-
- mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_ANON, count[0]);
- mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE, count[1]);
-}
-
/* Similar to reclaim, but different enough that they don't share logic */
static bool too_many_isolated(struct zone *zone)
{
@@ -866,6 +850,8 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
/* Successfully isolated */
del_page_from_lru_list(page, lruvec, page_lru(page));
+ inc_node_page_state(page,
+ NR_ISOLATED_ANON + page_is_file_cache(page));
isolate_success:
list_add(&page->lru, &cc->migratepages);
@@ -902,7 +888,6 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
spin_unlock_irqrestore(zone_lru_lock(zone), flags);
locked = false;
}
- acct_isolated(zone, cc);
putback_movable_pages(&cc->migratepages);
cc->nr_migratepages = 0;
cc->last_migrated_pfn = 0;
@@ -988,7 +973,6 @@ isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn,
if (cc->nr_migratepages == COMPACT_CLUSTER_MAX)
break;
}
- acct_isolated(cc->zone, cc);
return pfn;
}
@@ -1258,10 +1242,8 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
low_pfn = isolate_migratepages_block(cc, low_pfn,
block_end_pfn, isolate_mode);
- if (!low_pfn || cc->contended) {
- acct_isolated(zone, cc);
+ if (!low_pfn || cc->contended)
return ISOLATE_ABORT;
- }
/*
* Either we isolated something and proceed with migration. Or
@@ -1271,7 +1253,6 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
break;
}
- acct_isolated(zone, cc);
/* Record where migration scanner will be restarted. */
cc->migrate_pfn = low_pfn;
diff --git a/mm/migrate.c b/mm/migrate.c
index 99250aee1ac1..66ce6b490b13 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -168,8 +168,6 @@ void putback_movable_pages(struct list_head *l)
continue;
}
list_del(&page->lru);
- dec_node_page_state(page, NR_ISOLATED_ANON +
- page_is_file_cache(page));
/*
* We isolated non-lru movable page so here we can use
* __PageMovable because LRU page's mapping cannot have
@@ -186,6 +184,8 @@ void putback_movable_pages(struct list_head *l)
put_page(page);
} else {
putback_lru_page(page);
+ dec_node_page_state(page, NR_ISOLATED_ANON +
+ page_is_file_cache(page));
}
}
}
@@ -1121,8 +1121,15 @@ static ICE_noinline int unmap_and_move(new_page_t get_new_page,
* restored.
*/
list_del(&page->lru);
- dec_node_page_state(page, NR_ISOLATED_ANON +
- page_is_file_cache(page));
+
+ /*
+ * Compaction can migrate also non-LRU pages which are
+ * not accounted to NR_ISOLATED_*. They can be recognized
+ * as __PageMovable
+ */
+ if (likely(!__PageMovable(page)))
+ dec_node_page_state(page, NR_ISOLATED_ANON +
+ page_is_file_cache(page));
}
/*