* [patch] mm: memcontrol: clarify migration where old page is uncharged
@ 2014-10-19 15:30 Johannes Weiner
2014-10-20 19:45 ` Michal Hocko
0 siblings, 1 reply; 2+ messages in thread
From: Johannes Weiner @ 2014-10-19 15:30 UTC (permalink / raw)
To: Andrew Morton; +Cc: Hugh Dickins, Michal Hocko, linux-mm, cgroups, linux-kernel
Better explain re-entrant migration when compaction races with
reclaim, and also mention swapcache readahead pages as possible
uncharged migration sources.
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
---
mm/memcontrol.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index fc1d7ca96b9d..76892eb89d26 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6166,7 +6166,12 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage,
if (PageCgroupUsed(pc))
return;
- /* Re-entrant migration: old page already uncharged? */
+ /*
+ * Swapcache readahead pages can get migrated before being
+ * charged, and migration from compaction can happen to an
+ * uncharged page when the PFN walker finds a page that
+ * reclaim just put back on the LRU but has not released yet.
+ */
pc = lookup_page_cgroup(oldpage);
if (!PageCgroupUsed(pc))
return;
--
2.1.2
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [patch] mm: memcontrol: clarify migration where old page is uncharged
2014-10-19 15:30 [patch] mm: memcontrol: clarify migration where old page is uncharged Johannes Weiner
@ 2014-10-20 19:45 ` Michal Hocko
0 siblings, 0 replies; 2+ messages in thread
From: Michal Hocko @ 2014-10-20 19:45 UTC (permalink / raw)
To: Johannes Weiner
Cc: Andrew Morton, Hugh Dickins, linux-mm, cgroups, linux-kernel
On Sun 19-10-14 11:30:47, Johannes Weiner wrote:
> Better explain re-entrant migration when compaction races with
> reclaim, and also mention swapcache readahead pages as possible
> uncharged migration sources.
>
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
> ---
> mm/memcontrol.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index fc1d7ca96b9d..76892eb89d26 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -6166,7 +6166,12 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage,
> if (PageCgroupUsed(pc))
> return;
>
> - /* Re-entrant migration: old page already uncharged? */
> + /*
> + * Swapcache readahead pages can get migrated before being
> + * charged, and migration from compaction can happen to an
> + * uncharged page when the PFN walker finds a page that
> + * reclaim just put back on the LRU but has not released yet.
> + */
> pc = lookup_page_cgroup(oldpage);
> if (!PageCgroupUsed(pc))
> return;
> --
> 2.1.2
>
--
Michal Hocko
SUSE Labs
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2014-10-20 19:45 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2014-10-19 15:30 [patch] mm: memcontrol: clarify migration where old page is uncharged Johannes Weiner
2014-10-20 19:45 ` Michal Hocko
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).