linux-kernel - [PATCH 0/4] Better split_huge_page

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Message-ID: <20250806022045.342824-1-ziy@nvidia.com>
Date: Tue,  5 Aug 2025 22:20:41 -0400
From: Zi Yan <ziy@...dia.com>
To: David Hildenbrand <david@...hat.com>,
	linux-mm@...ck.org
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Zi Yan <ziy@...dia.com>,
	Baolin Wang <baolin.wang@...ux.alibaba.com>,
	"Liam R. Howlett" <Liam.Howlett@...cle.com>,
	Nico Pache <npache@...hat.com>,
	Ryan Roberts <ryan.roberts@....com>,
	Dev Jain <dev.jain@....com>,
	Barry Song <baohua@...nel.org>,
	Vlastimil Babka <vbabka@...e.cz>,
	Mike Rapoport <rppt@...nel.org>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Michal Hocko <mhocko@...e.com>,
	Shuah Khan <shuah@...nel.org>,
	linux-kernel@...r.kernel.org,
	linux-kselftest@...r.kernel.org
Subject: [PATCH 0/4] Better split_huge_page_test result check

David asked me if there is a way of checking split_huge_page_test
results instead of the existing smap check[1]. This patchset uses
kpageflags to get after-split folio orders for a better
split_huge_page_test result check. The added gather_folio_orders() scans
through a VPN range and collects the numbers of folios at different orders.
check_folio_orders() compares the result of gather_folio_orders() to
a given list of numbers of different orders.

split_huge_page_test needs the FORCE_READ fix in [2] to work correctly.

This patchset also:
1. added new order and in folio offset to the split huge page debugfs's
   pr_debug()s;
2. changed split_huge_pages_pid() to skip the rest of a folio if it is
   split by folio_split() (not changing split_folio_to_order() part
   since split_pte_mapped_thp test relies on its behavior).

[1] https://lore.kernel.org/linux-mm/e2f32bdb-e4a4-447c-867c-31405cbba151@redhat.com/
[2] https://lore.kernel.org/linux-mm/20250805175140.241656-1-ziy@nvidia.com/

Zi Yan (4):
  mm/huge_memory: add new_order and offset to split_huge_pages*()
    pr_debug.
  mm/huge_memory: move to next folio after folio_split() succeeds.
  selftests/mm: add check_folio_orders() helper.
  selftests/mm: check after-split folio orders in split_huge_page_test.

 mm/huge_memory.c                              |  22 +--
 .../selftests/mm/split_huge_page_test.c       |  67 ++++++---
 tools/testing/selftests/mm/vm_util.c          | 139 ++++++++++++++++++
 tools/testing/selftests/mm/vm_util.h          |   2 +
 4 files changed, 200 insertions(+), 30 deletions(-)

-- 
2.47.2