From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C7DF71E376C for ; Sat, 6 Jun 2026 00:18:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780705089; cv=none; b=WtBVrrSCR0A/r3Y/bFkDtNMsIYWF0i7QV9BAw922Jhl4USXRXj5GnIEkH22ywzfWLXDmrUE7HxM7JDtfBtnBbDUAtvsVJKaEe7mnN7mHlE3qVoEWQLiP9C29U3qCzHf7Kxvw1uKuRNGbv/L6gbPvM+3DMlVsSZRfnEBvnM/M584= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780705089; c=relaxed/simple; bh=wldGtdhDTa3LX4v6zvlJsdSNNSTxp09zgzsfMneyyrc=; h=Date:To:From:Subject:Message-Id; b=EKO/MkJX2gD1p7R0ZwBS5OCabNmmAWlmYT4qlGuHf7bpHAEg5upbV/P5EXK997XRfKC1y0yPCzMxtJmda3z3Z6d39n2j6o5L1srbK0e7M/J/RKCaxTeZUdr/OG2d7nRubwa7lRSwmN+ibpCyWrTzyaRvBkyL+mZql8peXeeoyII= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=szJZS6Ab; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="szJZS6Ab" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 939B91F00893; Sat, 6 Jun 2026 00:18:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1780705087; bh=doMiiVOCK44OrqGQoZOZpnNTTJxeQjnAGFE60RFQ53o=; h=Date:To:From:Subject; b=szJZS6Ab1HLVAVvYZYGWAoquRpLpAx0Yl/3rZ0fva9Weg6zNgNG7RABjMDSXuAS/e bk6Gl7vZ9O7gkiXNvrOqK5NDoe7Lko/PHKcbNvxoGdKuNVC3yqqaNq8OJga9Y3ISc9 glemrC45oGIt8ceLAV6gAKkMkJxAFqgIXK502F50= Date: Fri, 05 Jun 2026 17:18:07 -0700 To: mm-commits@vger.kernel.org,npache@redhat.com,akpm@linux-foundation.org From: Andrew Morton Subject: [to-be-updated] mm-khugepaged-add-per-order-mthp-collapse-failure-statistics.patch removed from -mm tree Message-Id: <20260606001807.939B91F00893@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The quilt patch titled Subject: mm/khugepaged: add per-order mTHP collapse failure statistics has been removed from the -mm tree. Its filename was mm-khugepaged-add-per-order-mthp-collapse-failure-statistics.patch This patch was dropped because an updated version will be issued ------------------------------------------------------ From: Nico Pache Subject: mm/khugepaged: add per-order mTHP collapse failure statistics Date: Fri, 22 May 2026 09:00:03 -0600 Add three new mTHP statistics to track collapse failures for different orders when encountering swap PTEs, excessive none PTEs, and shared PTEs: - collapse_exceed_swap_pte: Increment when mTHP collapse fails due to encountering a swap PTE. - collapse_exceed_none_pte: Counts when mTHP collapse fails due to exceeding the none PTE threshold for the given order - collapse_exceed_shared_pte: Counts when mTHP collapse fails due to encountering a shared PTE. These statistics complement the existing THP_SCAN_EXCEED_* events by providing per-order granularity for mTHP collapse attempts. The stats are exposed via sysfs under `/sys/kernel/mm/transparent_hugepage/hugepages-*/stats/` for each supported hugepage size. As we currently do not support collapsing mTHPs that contain a swap or shared entry, those statistics keep track of how often we are encountering failed mTHP collapses due to these restrictions. We will add support for mTHP collapse for anonymous pages next; lets also track when this happens at the PMD level within the per-mTHP stats. Link: https://lore.kernel.org/20260522150009.121603-9-npache@redhat.com Signed-off-by: Nico Pache Acked-by: David Hildenbrand (Arm) Reviewed-by: Lorenzo Stoakes Cc: Alistair Popple Cc: Andrea Arcangeli Cc: Anshuman Khandual Cc: Bagas Sanjaya Cc: Baolin Wang Cc: Barry Song Cc: Brendan Jackman Cc: Byungchul Park Cc: Catalin Marinas Cc: David Rientjes Cc: Dev Jain Cc: Gregory Price Cc: "Huang, Ying" Cc: Hugh Dickins Cc: Jan Kara Cc: Jann Horn Cc: Johannes Weiner Cc: Jonathan Corbet Cc: Joshua Hahn Cc: Kefeng Wang Cc: Lance Yang Cc: Liam R. Howlett Cc: "Masami Hiramatsu (Google)" Cc: Mathieu Desnoyers Cc: Matthew Brost Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Mike Rapoport Cc: Nanyong Sun Cc: Pedro Falcato Cc: Peter Xu Cc: Rafael Aquini Cc: Rakie Kim Cc: Randy Dunlap Cc: Ryan Roberts Cc: Shivank Garg Cc: Steven Rostedt Cc: Suren Baghdasaryan Cc: Takashi Iwai (SUSE) Cc: Thomas Hellström Cc: Usama Arif Cc: Usama Arif Cc: Vishal Moola (Oracle) Cc: Vlastimil Babka Cc: Wei Yang Cc: Will Deacon Cc: Yang Shi Cc: Zach O'Keefe Cc: Zi Yan Signed-off-by: Andrew Morton --- Documentation/admin-guide/mm/transhuge.rst | 14 ++++++++++++ include/linux/huge_mm.h | 3 ++ mm/huge_memory.c | 7 ++++++ mm/khugepaged.c | 21 +++++++++++++++++-- 4 files changed, 43 insertions(+), 2 deletions(-) --- a/Documentation/admin-guide/mm/transhuge.rst~mm-khugepaged-add-per-order-mthp-collapse-failure-statistics +++ a/Documentation/admin-guide/mm/transhuge.rst @@ -714,6 +714,20 @@ nr_anon_partially_mapped an anonymous THP as "partially mapped" and count it here, even though it is not actually partially mapped anymore. +collapse_exceed_none_pte + The number of collapse attempts that failed due to exceeding the + max_ptes_none threshold. + +collapse_exceed_swap_pte + The number of collapse attempts that failed due to exceeding the + max_ptes_swap threshold. For non-PMD orders this occurs if a mTHP range + contains at least one swap PTE. + +collapse_exceed_shared_pte + The number of collapse attempts that failed due to exceeding the + max_ptes_shared threshold. For non-PMD orders this occurs if a mTHP range + contains at least one shared PTE. + As the system ages, allocating huge pages may be expensive as the system uses memory compaction to copy data around memory to free a huge page for use. There are some counters in ``/proc/vmstat`` to help --- a/include/linux/huge_mm.h~mm-khugepaged-add-per-order-mthp-collapse-failure-statistics +++ a/include/linux/huge_mm.h @@ -144,6 +144,9 @@ enum mthp_stat_item { MTHP_STAT_SPLIT_DEFERRED, MTHP_STAT_NR_ANON, MTHP_STAT_NR_ANON_PARTIALLY_MAPPED, + MTHP_STAT_COLLAPSE_EXCEED_SWAP, + MTHP_STAT_COLLAPSE_EXCEED_NONE, + MTHP_STAT_COLLAPSE_EXCEED_SHARED, __MTHP_STAT_COUNT }; --- a/mm/huge_memory.c~mm-khugepaged-add-per-order-mthp-collapse-failure-statistics +++ a/mm/huge_memory.c @@ -720,6 +720,10 @@ DEFINE_MTHP_STAT_ATTR(split_failed, MTHP DEFINE_MTHP_STAT_ATTR(split_deferred, MTHP_STAT_SPLIT_DEFERRED); DEFINE_MTHP_STAT_ATTR(nr_anon, MTHP_STAT_NR_ANON); DEFINE_MTHP_STAT_ATTR(nr_anon_partially_mapped, MTHP_STAT_NR_ANON_PARTIALLY_MAPPED); +DEFINE_MTHP_STAT_ATTR(collapse_exceed_swap_pte, MTHP_STAT_COLLAPSE_EXCEED_SWAP); +DEFINE_MTHP_STAT_ATTR(collapse_exceed_none_pte, MTHP_STAT_COLLAPSE_EXCEED_NONE); +DEFINE_MTHP_STAT_ATTR(collapse_exceed_shared_pte, MTHP_STAT_COLLAPSE_EXCEED_SHARED); + static struct attribute *anon_stats_attrs[] = { &anon_fault_alloc_attr.attr, @@ -736,6 +740,9 @@ static struct attribute *anon_stats_attr &split_deferred_attr.attr, &nr_anon_attr.attr, &nr_anon_partially_mapped_attr.attr, + &collapse_exceed_swap_pte_attr.attr, + &collapse_exceed_none_pte_attr.attr, + &collapse_exceed_shared_pte_attr.attr, NULL, }; --- a/mm/khugepaged.c~mm-khugepaged-add-per-order-mthp-collapse-failure-statistics +++ a/mm/khugepaged.c @@ -651,7 +651,9 @@ static enum scan_result __collapse_huge_ if (pte_none_or_zero(pteval)) { if (++none_or_zero > max_ptes_none) { result = SCAN_EXCEED_NONE_PTE; - count_vm_event(THP_SCAN_EXCEED_NONE_PTE); + if (is_pmd_order(order)) + count_vm_event(THP_SCAN_EXCEED_NONE_PTE); + count_mthp_stat(order, MTHP_STAT_COLLAPSE_EXCEED_NONE); goto out; } continue; @@ -685,9 +687,17 @@ static enum scan_result __collapse_huge_ /* See collapse_scan_pmd(). */ if (folio_maybe_mapped_shared(folio)) { + /* + * TODO: Support shared pages without leading to further + * mTHP collapses. Currently bringing in new pages via + * shared may cause a future higher order collapse on a + * rescan of the same range. + */ if (++shared > max_ptes_shared) { result = SCAN_EXCEED_SHARED_PTE; - count_vm_event(THP_SCAN_EXCEED_SHARED_PTE); + if (is_pmd_order(order)) + count_vm_event(THP_SCAN_EXCEED_SHARED_PTE); + count_mthp_stat(order, MTHP_STAT_COLLAPSE_EXCEED_SHARED); goto out; } } @@ -1140,6 +1150,7 @@ static enum scan_result __collapse_huge_ * range. */ if (!is_pmd_order(order)) { + count_mthp_stat(order, MTHP_STAT_COLLAPSE_EXCEED_SWAP); pte_unmap(pte); mmap_read_unlock(mm); result = SCAN_EXCEED_SWAP_PTE; @@ -1447,6 +1458,8 @@ static enum scan_result collapse_scan_pm if (++none_or_zero > max_ptes_none) { result = SCAN_EXCEED_NONE_PTE; count_vm_event(THP_SCAN_EXCEED_NONE_PTE); + count_mthp_stat(HPAGE_PMD_ORDER, + MTHP_STAT_COLLAPSE_EXCEED_NONE); goto out_unmap; } continue; @@ -1455,6 +1468,8 @@ static enum scan_result collapse_scan_pm if (++unmapped > max_ptes_swap) { result = SCAN_EXCEED_SWAP_PTE; count_vm_event(THP_SCAN_EXCEED_SWAP_PTE); + count_mthp_stat(HPAGE_PMD_ORDER, + MTHP_STAT_COLLAPSE_EXCEED_SWAP); goto out_unmap; } /* @@ -1512,6 +1527,8 @@ static enum scan_result collapse_scan_pm if (++shared > max_ptes_shared) { result = SCAN_EXCEED_SHARED_PTE; count_vm_event(THP_SCAN_EXCEED_SHARED_PTE); + count_mthp_stat(HPAGE_PMD_ORDER, + MTHP_STAT_COLLAPSE_EXCEED_SHARED); goto out_unmap; } } _ Patches currently in -mm which might be from npache@redhat.com are mm-khugepaged-improve-tracepoints-for-mthp-orders.patch mm-khugepaged-introduce-collapse_allowable_orders-helper-function.patch mm-khugepaged-introduce-mthp-collapse-support.patch mm-khugepaged-introduce-mthp-collapse-support-fix.patch mm-khugepaged-avoid-unnecessary-mthp-collapse-attempts.patch documentation-mm-update-the-admin-guide-for-mthp-collapse.patch