On 05/20/2016 03:06 PM, Michal Hocko wrote:
On Thu 19-05-16 15:11:23, David Rientjes wrote:
If page migration fails due to -ENOMEM, nr_failed should still be
incremented for proper statistics.
This was encountered recently when all page migration vmstats showed 0,
and inferred that migrate_pages() was never called, although in reality
the first page migration failed because compaction_alloc() failed to find
a migration target.
This patch increments nr_failed so the vmstat is properly accounted on
ENOMEM.
Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
One question though
---
mm/migrate.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/mm/migrate.c b/mm/migrate.c
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1171,6 +1171,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
switch(rc) {
case -ENOMEM:
+ nr_failed++;
goto out;
case -EAGAIN:
retry++;
Why don't we need also to count also retries?
We could, but not like you suggest.
---
diff --git a/mm/migrate.c b/mm/migrate.c
index 53ab6398e7a2..ef9c5211ae3c 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1190,9 +1190,9 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
}
}
}
+out:
nr_failed += retry;
rc = nr_failed;
This overwrites rc == -ENOMEM, which at least compaction needs to
recognize. But we could duplicate "nr_failed += retry" in the case -ENOMEM.
-out:
if (nr_succeeded)
count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded);
if (nr_failed)
--
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