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 6F5771F2B88 for ; Sat, 6 Jun 2026 00:39:49 +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=1780706392; cv=none; b=txyYnKjy4ks+ECifhUgRrNIhoefB7dBItG2zh/jifUzNfnQPpWDU/nu4VVo8V2K3TgE1D2c7djQdju+IM+8zGe6/DrgyDGo4LIIVS7Sn+D2bAi6TqHmvshvW4vLGXwnRPpooX7cR6yj9PyBFElk69OFZZrEp2wxNerkiCbCV458= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780706392; c=relaxed/simple; bh=7yHGNEc/YbG3K93HhqVXGASO4krZDJJ2JVroYyOVso0=; h=Date:To:From:Subject:Message-Id; b=e4mL4GrTsTbtXhphsQy+tJE6MTGSxP+r+CWmU0GzcpvYEW+wecMtO9E3kS9b7HDbaxICdUC8x7La+qgvQnJk7rxJCrOuFqch6RoDZGcEWmyJz0PAgHz6fu/Ev0Awn9gOmM6dlRF+sGcESy2kOnJfDaV9tYIbgldTDyvh4SW3GvI= 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=2BqPs1Hj; 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="2BqPs1Hj" Received: by smtp.kernel.org (Postfix) with ESMTPSA id ECDB51F00898; Sat, 6 Jun 2026 00:39:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1780706389; bh=qlctEJtrOq+Acd+JIemHhzyPSk6R1tB3nDqjaue6Xus=; h=Date:To:From:Subject; b=2BqPs1HjwiB3bPu65BpXOkWTwN0t0Jknztu/6Bz8j9IZtcaDtrCDEDIykxo3nQuQG 8J006XxAjj+SRPmgK/ejwJNITtFED8ROJwDChHQgQ55vV8pMBu6of5DbwKbqzEqO7d /VIuttVqCAtC3OajeLE+jTAsg3Y08pw8uSgiyZdg= Date: Fri, 05 Jun 2026 17:39:48 -0700 To: mm-commits@vger.kernel.org,npache@redhat.com,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-khugepaged-add-per-order-mthp-collapse-failure-statistics.patch added to mm-unstable branch Message-Id: <20260606003948.ECDB51F00898@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm/khugepaged: add per-order mTHP collapse failure statistics has been added to the -mm mm-unstable branch. Its filename is mm-khugepaged-add-per-order-mthp-collapse-failure-statistics.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-khugepaged-add-per-order-mthp-collapse-failure-statistics.patch This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via various branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there most days ------------------------------------------------------ From: Nico Pache Subject: mm/khugepaged: add per-order mTHP collapse failure statistics Date: Fri, 5 Jun 2026 10:14:15 -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/20260605161422.213817-9-npache@redhat.com Signed-off-by: Nico Pache Reviewed-by: Lorenzo Stoakes Acked-by: David Hildenbrand (Arm) 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 | 15 +++++++++++++-- 4 files changed, 37 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; @@ -693,7 +695,9 @@ static enum scan_result __collapse_huge_ */ 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; } } @@ -1152,6 +1156,7 @@ 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; @@ -1464,6 +1469,8 @@ 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; @@ -1472,6 +1479,8 @@ 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; } /* @@ -1529,6 +1538,8 @@ 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-generalize-hugepage_vma_revalidate-for-mthp-support.patch mm-khugepaged-rework-max_ptes_-handling-with-helper-functions.patch mm-khugepaged-generalize-__collapse_huge_page_-for-mthp-support.patch mm-khugepaged-require-collapse_huge_page-to-enter-exit-with-the-lock-dropped.patch mm-khugepaged-generalize-collapse_huge_page-for-mthp-collapse.patch mm-khugepaged-skip-collapsing-mthp-to-smaller-orders.patch mm-khugepaged-add-per-order-mthp-collapse-failure-statistics.patch mm-khugepaged-improve-tracepoints-for-mthp-orders.patch mm-khugepaged-introduce-collapse_possible_orders-helper-functions.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