The patch titled
Subject: mm: hugetlb: avoid fallback for specific node allocation of 1G pages
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-hugetlb-avoid-fallback-for-specific-node-allocation-of-1g-pages.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-hugetlb-avoid-fallback-for-specific-node-allocation-of-1g-pages.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Luiz Capitulino <luizcap@xxxxxxxxxx>
Subject: mm: hugetlb: avoid fallback for specific node allocation of 1G pages
Date: Mon, 10 Feb 2025 22:48:56 -0500
When using the HugeTLB kernel command-line to allocate 1G pages from a
specific node, such as:
default_hugepagesz=1G hugepages=1:1
If node 1 happens to not have enough memory for the requested number of 1G
pages, the allocation falls back to other nodes. A quick way to reproduce
this is by creating a KVM guest with a memory-less node and trying to
allocate 1 1G page from it. Instead of failing, the allocation will
fallback to other nodes.
This defeats the purpose of node specific allocation. Also, specific node
allocation for 2M pages don't have this behavior: the allocation will just
fail for the pages it can't satisfy.
This issue happens because HugeTLB calls memblock_alloc_try_nid_raw() for
1G boot-time allocation as this function falls back to other nodes if the
allocation can't be satisfied. Use memblock_alloc_exact_nid_raw()
instead, which ensures that the allocation will only be satisfied from the
specified node.
Link: https://lkml.kernel.org/r/20250211034856.629371-1-luizcap@xxxxxxxxxx
Fixes: b5389086ad7b ("hugetlbfs: extend the definition of hugepages parameter to support node allocation")
Signed-off-by: Luiz Capitulino <luizcap@xxxxxxxxxx>
Acked-by: Oscar Salvador <osalvador@xxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: "Mike Rapoport (IBM)" <rppt@xxxxxxxxxx>
Cc: Muchun Song <muchun.song@xxxxxxxxx>
Cc: Zhenguo Yao <yaozhenguo1@xxxxxxxxx>
Cc: Frank van der Linden <fvdl@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/hugetlb.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/hugetlb.c~mm-hugetlb-avoid-fallback-for-specific-node-allocation-of-1g-pages
+++ a/mm/hugetlb.c
@@ -3145,7 +3145,7 @@ int __alloc_bootmem_huge_page(struct hst
/* do node specific alloc */
if (nid != NUMA_NO_NODE) {
- m = memblock_alloc_try_nid_raw(huge_page_size(h), huge_page_size(h),
+ m = memblock_alloc_exact_nid_raw(huge_page_size(h), huge_page_size(h),
0, MEMBLOCK_ALLOC_ACCESSIBLE, nid);
if (!m)
return 0;
_
Patches currently in -mm which might be from luizcap@xxxxxxxxxx are
mm-hugetlb-avoid-fallback-for-specific-node-allocation-of-1g-pages.patch
