linux-kernel - Re: [RFC PATCH] mm, hugetlb: implement movable_gigantic

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Message-ID: <aPZd1dAIzAw7Ii8E@gourry-fedora-PF4VCD3F>
Date: Mon, 20 Oct 2025 12:05:41 -0400
From: Gregory Price <gourry@...rry.net>
To: David Hildenbrand <david@...hat.com>
Cc: linux-mm@...ck.org, osalvador@...e.de, corbet@....net,
	muchun.song@...ux.dev, akpm@...ux-foundation.org,
	hannes@...xchg.org, laoar.shao@...il.com, mclapinski@...gle.com,
	joel.granados@...nel.org, jack@...e.cz, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, Mel Gorman <mgorman@...e.de>,
	Michal Hocko <mhocko@...e.com>,
	Alexandru Moise <00moses.alexander00@...il.com>,
	David Rientjes <rientjes@...gle.com>
Subject: Re: [RFC PATCH] mm, hugetlb: implement movable_gigantic_pages sysctl

On Mon, Oct 20, 2025 at 04:17:06PM +0200, David Hildenbrand wrote:
> On 09.10.25 18:15, Gregory Price wrote:
> That could be supported by allowing for moving hugetlb folios when their
> size is small enough to be served by the buddy, and the size we are
> allocating is larger than the one of these folios.
> 

I think this is roughly what you'd be looking for?
~Gregory

---

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 5549b32cdd31..5def2c53092e 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6922,8 +6922,12 @@ 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)) {
+                       /* Don't consider moving same size/larger pages */
+                       if (!CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION ||
+                           ((1 << compound_order(page)) >= nr_pages))
+                               return false;
+               }
        }
        return true;
 }