* [PATCH 0/1] mm/migrate: do not call prep_transhuge_page if !thp_migration_supported
@ 2017-11-20 16:17 Andrea Reale
2017-11-20 16:17 ` [PATCH 1/1] " Andrea Reale
0 siblings, 1 reply; 4+ messages in thread
From: Andrea Reale @ 2017-11-20 16:17 UTC (permalink / raw)
To: linux-kernel, zi.yan, n-horiguchi; +Cc: akpm, jglisse, realean2
Hi all,
While working on a second round of patches to introduce memory hotplug /
hot remove to arm64 (original attempt at [1]), and trying to rebase them
on 4.14, I stumbled in some problematic behaviour during page migration
when offlining for hot remove, whereas target pages for migration where
found in a bad state.
I believe that this behaviour may be originating from commit 8135d8926c08
("mm: memory_hotplug: memory hotremove supports thp migration")
and it is triggered when migrating pages for builds that have no
ARCH_ENABLE_THP_MIGRATION but have thp support on (arm64, in my case).
Specifically, my understanding is that prep_transhuge_page should not be
called in linux/migrate.h:new_page_nodemask if !thp_migration_supported
because, in that case, new_page would not be a thp.
A tiny patch follows, showing what I mean. Please, let me know if my
understanding is bogus.
Best regards,
Andrea
[1] https://lkml.org/lkml/2017/4/11/536
Andrea Reale (1):
mm/migrate: do not call prep_transhuge_page if
!thp_migration_supported
include/linux/migrate.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--
2.7.4
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH 1/1] mm/migrate: do not call prep_transhuge_page if !thp_migration_supported
2017-11-20 16:17 [PATCH 0/1] mm/migrate: do not call prep_transhuge_page if !thp_migration_supported Andrea Reale
@ 2017-11-20 16:17 ` Andrea Reale
2017-11-20 16:33 ` Zi Yan
0 siblings, 1 reply; 4+ messages in thread
From: Andrea Reale @ 2017-11-20 16:17 UTC (permalink / raw)
To: linux-kernel, zi.yan, n-horiguchi; +Cc: akpm, jglisse, realean2
new_page_nodemask in linux/migrate.h should not call prep_transhuge_page
if thp_migration_support is false.
Fixes commit 8135d8926c08 ("mm: memory_hotplug: memory hotremove supports
thp migration")
Signed-off-by: Andrea Reale <ar@linux.vnet.ibm.com>
---
include/linux/migrate.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index 895ec0c..725eac5 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -54,7 +54,7 @@ static inline struct page *new_page_nodemask(struct page *page,
new_page = __alloc_pages_nodemask(gfp_mask, order,
preferred_nid, nodemask);
- if (new_page && PageTransHuge(page))
+ if (thp_migration_supported() && new_page && PageTransHuge(page))
prep_transhuge_page(new_page);
return new_page;
--
2.7.4
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH 1/1] mm/migrate: do not call prep_transhuge_page if !thp_migration_supported
2017-11-20 16:17 ` [PATCH 1/1] " Andrea Reale
@ 2017-11-20 16:33 ` Zi Yan
2017-11-20 17:07 ` Andrea Reale
0 siblings, 1 reply; 4+ messages in thread
From: Zi Yan @ 2017-11-20 16:33 UTC (permalink / raw)
To: Andrea Reale; +Cc: linux-kernel, n-horiguchi, akpm, jglisse, realean2
[-- Attachment #1: Type: text/plain, Size: 1804 bytes --]
Hi Andrea,
Thanks for pointing this out.
I think the problem is that we should not prep_transhuge_page(new_page)
unless new_page is allocated and PageTransHuge(). And several lines above,
the allocation flags and the order is changed to make new_page a THP
only if thp_migration_supported() is true.
Does the patch below look better?
diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index 895ec0c..725eac5 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -54,7 +54,7 @@ static inline struct page *new_page_nodemask(struct page *page,
new_page = __alloc_pages_nodemask(gfp_mask, order,
preferred_nid, nodemask);
- if (new_page && PageTransHuge(page))
+ if (new_page && PageTransHuge(new_page))
prep_transhuge_page(new_page);
return new_page;
--
--
Best Regards
Yan Zi
On 20 Nov 2017, at 11:17, Andrea Reale wrote:
> new_page_nodemask in linux/migrate.h should not call prep_transhuge_page
> if thp_migration_support is false.
>
> Fixes commit 8135d8926c08 ("mm: memory_hotplug: memory hotremove supports
> thp migration")
>
> Signed-off-by: Andrea Reale <ar@linux.vnet.ibm.com>
> ---
> include/linux/migrate.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/migrate.h b/include/linux/migrate.h
> index 895ec0c..725eac5 100644
> --- a/include/linux/migrate.h
> +++ b/include/linux/migrate.h
> @@ -54,7 +54,7 @@ static inline struct page *new_page_nodemask(struct page *page,
> new_page = __alloc_pages_nodemask(gfp_mask, order,
> preferred_nid, nodemask);
>
> - if (new_page && PageTransHuge(page))
> + if (thp_migration_supported() && new_page && PageTransHuge(page))
> prep_transhuge_page(new_page);
>
> return new_page;
> --
> 2.7.4
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^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH 1/1] mm/migrate: do not call prep_transhuge_page if !thp_migration_supported
2017-11-20 16:33 ` Zi Yan
@ 2017-11-20 17:07 ` Andrea Reale
0 siblings, 0 replies; 4+ messages in thread
From: Andrea Reale @ 2017-11-20 17:07 UTC (permalink / raw)
To: Zi Yan; +Cc: linux-kernel, n-horiguchi, akpm, jglisse, realean2
Hi Yan Zi,
thanks for the feedback. Yes, it looks definitely less redundant :)
Regards,
Andrea
On Mon, Nov 20, 2017 at 11:33:06AM -0500, Zi Yan wrote:
> Hi Andrea,
>
> Thanks for pointing this out.
>
> I think the problem is that we should not prep_transhuge_page(new_page)
> unless new_page is allocated and PageTransHuge(). And several lines above,
> the allocation flags and the order is changed to make new_page a THP
> only if thp_migration_supported() is true.
>
> Does the patch below look better?
>
> diff --git a/include/linux/migrate.h b/include/linux/migrate.h
> index 895ec0c..725eac5 100644
> --- a/include/linux/migrate.h
> +++ b/include/linux/migrate.h
> @@ -54,7 +54,7 @@ static inline struct page *new_page_nodemask(struct page *page,
> new_page = __alloc_pages_nodemask(gfp_mask, order,
> preferred_nid, nodemask);
>
> - if (new_page && PageTransHuge(page))
> + if (new_page && PageTransHuge(new_page))
> prep_transhuge_page(new_page);
>
> return new_page;
> --
>
>
> --
> Best Regards
> Yan Zi
>
> On 20 Nov 2017, at 11:17, Andrea Reale wrote:
>
> > new_page_nodemask in linux/migrate.h should not call prep_transhuge_page
> > if thp_migration_support is false.
> >
> > Fixes commit 8135d8926c08 ("mm: memory_hotplug: memory hotremove supports
> > thp migration")
> >
> > Signed-off-by: Andrea Reale <ar@linux.vnet.ibm.com>
> > ---
> > include/linux/migrate.h | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/include/linux/migrate.h b/include/linux/migrate.h
> > index 895ec0c..725eac5 100644
> > --- a/include/linux/migrate.h
> > +++ b/include/linux/migrate.h
> > @@ -54,7 +54,7 @@ static inline struct page *new_page_nodemask(struct page *page,
> > new_page = __alloc_pages_nodemask(gfp_mask, order,
> > preferred_nid, nodemask);
> >
> > - if (new_page && PageTransHuge(page))
> > + if (thp_migration_supported() && new_page && PageTransHuge(page))
> > prep_transhuge_page(new_page);
> >
> > return new_page;
> > --
> > 2.7.4
^ permalink raw reply [flat|nested] 4+ messages in thread
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2017-11-20 16:33 ` Zi Yan
2017-11-20 17:07 ` Andrea Reale
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