From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 CC6FC386557 for ; Mon, 11 May 2026 20:56:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778532965; cv=none; b=thAnOBVBMGB9ZB8m002m9667eze1fXcyW+34WIGL1kVnEYtbcuAAzdrHGtjpXj0mrnvOdPOM6HC1gcTscLMJuQ7miXJoT20DCIwqME9IRd4L19iJethhj5yHVzoU4SUQT1K+hH6KdstAjmHOuvWTRvHpA6Sg7GqM04tS2FzPWZ4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778532965; c=relaxed/simple; bh=WHxg+vROKDE4H+WBHMRNXIps/94qOVyVp3FSXg1ae1Y=; h=Date:To:From:Subject:Message-Id; b=nT1l31//B1eR8SnyVO4bUWbMBYhOGHwQ38XQEW/dV5p67HnTYzUoP4MuTn9c8q6gE13/XsbAPekGZ4p5/yhaWDN4YurgUSsLxPXtdxYp8+ii/6lcz6BJtRXNxdEVe45pbvH2jWmXGa+pVqgrkYwkZE9SvrZbccvJ7wF4mF9Wy9g= 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=1HhR+IkE; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="1HhR+IkE" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8F6D4C2BCB0; Mon, 11 May 2026 20:56:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1778532965; bh=WHxg+vROKDE4H+WBHMRNXIps/94qOVyVp3FSXg1ae1Y=; h=Date:To:From:Subject:From; b=1HhR+IkE/yxVvl+B0lNuxVhx2YNlKummR01SgPLcJnw4H+6paw2K9Ncrb4OyboWBA w4wzoaJhbcdUAD//F/4rKr1YmZaYnBTvpF+0z8Fl/dL6ClLiq+9M9RrZc0ta1XIMeW NWXvxbwnhzCgjtkQTCc7GzSRKQPwxBw7zFnje0TM= Date: Mon, 11 May 2026 13:56:05 -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: <20260511205605.8F6D4C2BCB0@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: Sun, 19 Apr 2026 12:57:44 -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 swap PTEs - 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 shared PTEs 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 dont 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. Now that we plan to support mTHP collapse for anon pages, lets also track when this happens at the PMD level within the per-mTHP stats. Link: https://lore.kernel.org/20260419185750.260784-8-npache@redhat.com Signed-off-by: Nico Pache 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 Hildenbrand (Arm) 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 Howlett Cc: Lorenzo Stoakes 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: 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 | 24 +++++++++++++++++++ include/linux/huge_mm.h | 3 ++ mm/huge_memory.c | 7 +++++ mm/khugepaged.c | 21 +++++++++++++++- 4 files changed, 53 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 +714,30 @@ 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. For mTHP collapse, Currently only max_ptes_none + values of 0 and (HPAGE_PMD_NR - 1) are supported. Any other value will + emit a warning and no mTHP collapse will be attempted. khugepaged will + try to collapse to the largest enabled (m)THP size; if it fails, it will + try the next lower enabled mTHP size. This counter records the number of + times a collapse attempt was skipped for exceeding the max_ptes_none + threshold, and khugepaged will move on to the next available mTHP size. + +collapse_exceed_swap_pte + The number of anonymous mTHP PTE ranges which were unable to collapse due + to containing at least one swap PTE. Currently khugepaged does not + support collapsing mTHP regions that contain a swap PTE. This counter can + be used to monitor the number of khugepaged mTHP collapses that failed + due to the presence of a swap PTE. + +collapse_exceed_shared_pte + The number of anonymous mTHP PTE ranges which were unable to collapse due + to containing at least one shared PTE. Currently khugepaged does not + support collapsing mTHP PTE ranges that contain a shared PTE. This + counter can be used to monitor the number of khugepaged mTHP collapses + that failed due to the presence of a 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 @@ -717,6 +717,10 @@ 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, @@ -733,6 +737,9 @@ 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 @@ -646,7 +646,9 @@ 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; @@ -680,9 +682,17 @@ 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; } } @@ -1129,6 +1139,7 @@ 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; @@ -1412,6 +1423,8 @@ 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; @@ -1420,6 +1433,8 @@ 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; } /* @@ -1477,6 +1492,8 @@ 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-avoid-unnecessary-mthp-collapse-attempts.patch documentation-mm-update-the-admin-guide-for-mthp-collapse.patch