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Fri, 05 Jun 2026 12:16:17 -0400 X-MC-Unique: FPwph6UcNQyD_L1sHVgsEg-1 X-Mimecast-MFC-AGG-ID: FPwph6UcNQyD_L1sHVgsEg_1780676176 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 42D9D18002C1; Fri, 5 Jun 2026 16:16:16 +0000 (UTC) Received: from p1.redhat.com (unknown [10.44.22.9]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id CD408180049F; Fri, 5 Jun 2026 16:15:57 +0000 (UTC) From: Nico Pache To: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org Cc: aarcange@redhat.com, akpm@linux-foundation.org, anshuman.khandual@arm.com, apopple@nvidia.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, byungchul@sk.com, catalin.marinas@arm.com, cl@gentwo.org, corbet@lwn.net, dave.hansen@linux.intel.com, david@kernel.org, dev.jain@arm.com, gourry@gourry.net, hannes@cmpxchg.org, hughd@google.com, jack@suse.cz, jackmanb@google.com, jannh@google.com, jglisse@google.com, joshua.hahnjy@gmail.com, kas@kernel.org, lance.yang@linux.dev, liam@infradead.org, ljs@kernel.org, mathieu.desnoyers@efficios.com, matthew.brost@intel.com, mhiramat@kernel.org, mhocko@suse.com, npache@redhat.com, peterx@redhat.com, pfalcato@suse.de, rakie.kim@sk.com, raquini@redhat.com, rdunlap@infradead.org, richard.weiyang@gmail.com, rientjes@google.com, rostedt@goodmis.org, rppt@kernel.org, ryan.roberts@arm.com, shivankg@amd.com, sunnanyong@huawei.com, surenb@google.com, thomas.hellstrom@linux.intel.com, tiwai@suse.de, usamaarif642@gmail.com, vbabka@suse.cz, vishal.moola@gmail.com, wangkefeng.wang@huawei.com, will@kernel.org, willy@infradead.org, yang@os.amperecomputing.com, ying.huang@linux.alibaba.com, ziy@nvidia.com, zokeefe@google.com Subject: [PATCH mm-unstable v19 08/14] mm/khugepaged: add per-order mTHP collapse failure statistics Date: Fri, 5 Jun 2026 10:14:15 -0600 Message-ID: <20260605161422.213817-9-npache@redhat.com> In-Reply-To: <20260605161422.213817-1-npache@redhat.com> References: <20260605161422.213817-1-npache@redhat.com> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 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. Reviewed-by: Lorenzo Stoakes Acked-by: David Hildenbrand (Arm) Signed-off-by: Nico Pache --- 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(-) diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst index a74844e01f1e..b98e18c80185 100644 --- a/Documentation/admin-guide/mm/transhuge.rst +++ b/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 diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h index 443852423790..148109ebd08a 100644 --- a/include/linux/huge_mm.h +++ b/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 }; diff --git a/mm/huge_memory.c b/mm/huge_memory.c index eea83da9114a..222e421d9e8e 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -717,6 +717,10 @@ DEFINE_MTHP_STAT_ATTR(split_failed, MTHP_STAT_SPLIT_FAILED); 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_attrs[] = { &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, }; diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 191e529c185c..ac4731addafa 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -651,7 +651,9 @@ static enum scan_result __collapse_huge_page_isolate(struct vm_area_struct *vma, 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_page_isolate(struct vm_area_struct *vma, */ 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_page_swapin(struct mm_struct *mm, * 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; @@ -1459,6 +1464,8 @@ static enum scan_result collapse_scan_pmd(struct mm_struct *mm, 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; @@ -1467,6 +1474,8 @@ static enum scan_result collapse_scan_pmd(struct mm_struct *mm, 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; } /* @@ -1524,6 +1533,8 @@ static enum scan_result collapse_scan_pmd(struct mm_struct *mm, 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; } } -- 2.54.0