+ hugetlb-add-cond_resched-to-__unmap_hugepage_range.patch added to mm-unstable branch

The patch titled
     Subject: hugetlb: add cond_resched() to __unmap_hugepage_range()
has been added to the -mm mm-unstable branch.  Its filename is
     hugetlb-add-cond_resched-to-__unmap_hugepage_range.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/hugetlb-add-cond_resched-to-__unmap_hugepage_range.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Leon Hwang <[email protected]>
Subject: hugetlb: add cond_resched() to __unmap_hugepage_range()
Date: Tue, 18 Aug 2026 21:50:29 +0800

Packet receive timeouts were traced to sparse HugeTLB unmapping in
production.  A task unmapping a sparse 2.5 TiB HugeTLB mapping could
remain in kernel context for over 40 ms without reaching a scheduling
point while walking empty huge PTEs.  Although hard IRQs could still be
handled, the per-CPU ksoftirqd thread and other runnable tasks could not
run during that interval, delaying NET_RX softirq work queued to
ksoftirqd.

Add cond_resched() at the beginning of the hugepage loop so ksoftirqd and
other runnable tasks can run between iterations.  Testing with
PREEMPT_NONE showed that the maximum interval between scheduling points
fell from over 40 ms to below 2.5 ms.  Total time spent in
__unmap_hugepage_range() remained about 36 ms.

Link: https://lore.kernel.org/[email protected]
Signed-off-by: Leon Hwang <[email protected]>
Reported-by: Lance Yang <[email protected]>
Tested-by: Lance Yang <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Muchun Song <[email protected]>
Cc: Oscar Salvador <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---

 mm/hugetlb.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/mm/hugetlb.c~hugetlb-add-cond_resched-to-__unmap_hugepage_range
+++ a/mm/hugetlb.c
@@ -5235,6 +5235,8 @@ void __unmap_hugepage_range(struct mmu_g
 	last_addr_mask = hugetlb_mask_last_page(h);
 	address = start;
 	for (; address < end; address += sz) {
+		cond_resched();
+
 		ptep = hugetlb_walk(vma, address, sz);
 		if (!ptep) {
 			address |= last_addr_mask;
_

Patches currently in -mm which might be from [email protected] are

hugetlb-add-cond_resched-to-__unmap_hugepage_range.patch