On Mon, Jul 13, 2020 at 09:52:20AM +0200, Vlastimil Babka wrote:
> On 7/13/20 8:41 AM, js1304@xxxxxxxxx wrote:
> > From: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
> >
> > new_page_nodemask is a migration callback and it tries to use a common
> > gfp flags for the target page allocation whether it is a base page or a
> > THP. The later only adds GFP_TRANSHUGE to the given mask. This results
> > in the allocation being slightly more aggressive than necessary because
> > the resulting gfp mask will contain also __GFP_RECLAIM_KSWAPD. THP
> > allocations usually exclude this flag to reduce over eager background
> > reclaim during a high THP allocation load which has been seen during
> > large mmaps initialization. There is no indication that this is a
> > problem for migration as well but theoretically the same might happen
> > when migrating large mappings to a different node. Make the migration
> > callback consistent with regular THP allocations.
> >
> > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
>
> Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
>
> Thanks!
>
> Typo below (I assume Andrew will fix it)
>
> > ---
> > mm/migrate.c | 5 +++++
> > 1 file changed, 5 insertions(+)
> >
> > diff --git a/mm/migrate.c b/mm/migrate.c
> > index 3b3d918..1cfc965 100644
> > --- a/mm/migrate.c
> > +++ b/mm/migrate.c
> > @@ -1547,6 +1547,11 @@ struct page *new_page_nodemask(struct page *page,
> > }
> >
> > if (PageTransHuge(page)) {
> > + /*
> > + * clear __GFP_RECALIM to make the migration callback
>
> __GFP_RECLAIM
>
Okay. Here goes a fixed version.
Thanks!
---------------------->8-----------------------------
>From 6273f02fd8b8ef066c10c4a8ba54ea9efe6e70cd Mon Sep 17 00:00:00 2001
From: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Date: Mon, 6 Jul 2020 14:34:04 +0900
Subject: [PATCH v5 4/9] mm/migrate: clear __GFP_RECLAIM to make the migration
callback consistent with regular THP allocations
new_page_nodemask is a migration callback and it tries to use a common
gfp flags for the target page allocation whether it is a base page or a
THP. The later only adds GFP_TRANSHUGE to the given mask. This results
in the allocation being slightly more aggressive than necessary because
the resulting gfp mask will contain also __GFP_RECLAIM_KSWAPD. THP
allocations usually exclude this flag to reduce over eager background
reclaim during a high THP allocation load which has been seen during
large mmaps initialization. There is no indication that this is a
problem for migration as well but theoretically the same might happen
when migrating large mappings to a different node. Make the migration
callback consistent with regular THP allocations.
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
---
mm/migrate.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/mm/migrate.c b/mm/migrate.c
index 3b3d918..faabb2e 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1547,6 +1547,11 @@ struct page *new_page_nodemask(struct page *page,
}
if (PageTransHuge(page)) {
+ /*
+ * clear __GFP_RECLAIM to make the migration callback
+ * consistent with regular THP allocations.
+ */
+ gfp_mask &= ~__GFP_RECLAIM;
gfp_mask |= GFP_TRANSHUGE;
order = HPAGE_PMD_ORDER;
}
--
2.7.4
