[PATCH v3] page_alloc: allow migration of smaller hugepages during contig_alloc.

[PATCH v3] page_alloc: allow migration of smaller hugepages during contig_alloc.

[Gregory Price]

We presently skip regions with hugepages entirely when trying to do
contiguous page allocation.  Instead, if hugepage migration is enabled,
consider regions with hugepages smaller than the target contiguous
allocation request as valid targets for allocation.

isolate_migrate_pages_block() already expects requests with hugepages
to originate from alloc_contig, and hugetlb code also does a migratable
check when isolating in folio_isolate_hugetlb().

Suggested-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Gregory Price <gourry@gourry.net>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
---
 mm/page_alloc.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 600d9e981c23..23866d4c26ff 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -7048,8 +7048,19 @@ static bool pfn_range_valid_contig(struct zone *z, unsigned long start_pfn,
 		if (PageReserved(page))
 			return false;
 
-		if (PageHuge(page))
-			return false;
+		if (PageHuge(page)) {
+			unsigned int order;
+
+			if (!IS_ENABLED(CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION))
+				return false;
+
+			/* Don't consider moving same size/larger pages */
+			page = compound_head(page);
+			order = compound_order(page);
+			if ((order >= MAX_FOLIO_ORDER) ||
+			    (nr_pages <= (1 << order)))
+				return false;
+		}
 	}
 	return true;
 }
-- 
2.51.0

Re: [PATCH v3] page_alloc: allow migration of smaller hugepages during contig_alloc.

[David Rientjes]

On Fri, 24 Oct 2025, Gregory Price wrote:

> We presently skip regions with hugepages entirely when trying to do
> contiguous page allocation.  Instead, if hugepage migration is enabled,
> consider regions with hugepages smaller than the target contiguous
> allocation request as valid targets for allocation.
> 
> isolate_migrate_pages_block() already expects requests with hugepages
> to originate from alloc_contig, and hugetlb code also does a migratable
> check when isolating in folio_isolate_hugetlb().
> 
> Suggested-by: David Hildenbrand <david@redhat.com>
> Signed-off-by: Gregory Price <gourry@gourry.net>
> Reviewed-by: Zi Yan <ziy@nvidia.com>
> Reviewed-by: Wei Yang <richard.weiyang@gmail.com>

Acked-by: David Rientjes <rientjes@google.com>

Re: [PATCH v3] page_alloc: allow migration of smaller hugepages during contig_alloc.

[Oscar Salvador]

On Fri, Oct 24, 2025 at 03:28:49PM -0400, Gregory Price wrote:
> We presently skip regions with hugepages entirely when trying to do
> contiguous page allocation.  Instead, if hugepage migration is enabled,
> consider regions with hugepages smaller than the target contiguous
> allocation request as valid targets for allocation.
> 
> isolate_migrate_pages_block() already expects requests with hugepages
> to originate from alloc_contig, and hugetlb code also does a migratable
> check when isolating in folio_isolate_hugetlb().
> 
> Suggested-by: David Hildenbrand <david@redhat.com>
> Signed-off-by: Gregory Price <gourry@gourry.net>
> Reviewed-by: Zi Yan <ziy@nvidia.com>
> Reviewed-by: Wei Yang <richard.weiyang@gmail.com>

Reviewed-by: Oscar Salvador <osalvador@suse.de>

 

-- 
Oscar Salvador
SUSE Labs

Re: [PATCH v3] page_alloc: allow migration of smaller hugepages during contig_alloc.

[David Hildenbrand]

On 24.10.25 21:28, Gregory Price wrote:
> We presently skip regions with hugepages entirely when trying to do
> contiguous page allocation.  Instead, if hugepage migration is enabled,
> consider regions with hugepages smaller than the target contiguous
> allocation request as valid targets for allocation.
> 
> isolate_migrate_pages_block() already expects requests with hugepages
> to originate from alloc_contig, and hugetlb code also does a migratable
> check when isolating in folio_isolate_hugetlb().
> 
> Suggested-by: David Hildenbrand <david@redhat.com>
> Signed-off-by: Gregory Price <gourry@gourry.net>
> Reviewed-by: Zi Yan <ziy@nvidia.com>
> Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
> ---

Nit: trailing "." in subject

Acked-by: David Hildenbrand <david@redhat.com>

-- 
Cheers

David / dhildenb

Re: [PATCH v3] page_alloc: allow migration of smaller hugepages during contig_alloc.

[Gregory Price]

On Mon, Oct 27, 2025 at 04:43:25PM +0100, David Hildenbrand wrote:
> On 24.10.25 21:28, Gregory Price wrote:
> > We presently skip regions with hugepages entirely when trying to do
> > contiguous page allocation.  Instead, if hugepage migration is enabled,
> > consider regions with hugepages smaller than the target contiguous
> > allocation request as valid targets for allocation.
> > 
> > isolate_migrate_pages_block() already expects requests with hugepages
> > to originate from alloc_contig, and hugetlb code also does a migratable
> > check when isolating in folio_isolate_hugetlb().
> > 
> > Suggested-by: David Hildenbrand <david@redhat.com>
> > Signed-off-by: Gregory Price <gourry@gourry.net>
> > Reviewed-by: Zi Yan <ziy@nvidia.com>
> > Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
> > ---
> 
> Nit: trailing "." in subject
> 
> Acked-by: David Hildenbrand <david@redhat.com>
>

Hi David,

Do you think i should just staple these commits together at this point?

https://lore.kernel.org/linux-mm/20251009161515.422292-1-gourry@gourry.net/

If not i'll drop the '.' and just resubmit this with tags and just
update the commit message on movable_gigantic_pages to reference this
commit and your notes from there.

~Gregory