From 42248b9d34ea1be1b959d343fff465906cb787fc Mon Sep 17 00:00:00 2001 From: Barry Song <v-songbaohua@oppo.com> Date: Fri, 12 Apr 2024 23:48:57 +1200 Subject: [PATCH] mm: add docs for per-order mTHP counters and transhuge_page ABI This patch includes documentation for mTHP counters and an ABI file for sys-kernel-mm-transparent-hugepage, which appears to have been missing for some time. [v-songbaohua@oppo.com: fix the name and unexpected indentation] Link: https://lkml.kernel.org/r/20240415054538.17071-1-21cnbao@gmail.com Link: https://lkml.kernel.org/r/20240412114858.407208-4-21cnbao@gmail.com Signed-off-by: Barry Song <v-songbaohua@oppo.com> Reviewed-by: Ryan Roberts <ryan.roberts@arm.com> Reviewed-by: David Hildenbrand <david@redhat.com> Cc: Chris Li <chrisl@kernel.org> Cc: Domenico Cerasuolo <cerasuolodomenico@gmail.com> Cc: Kairui Song <kasong@tencent.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Peter Xu <peterx@redhat.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Yosry Ahmed <yosryahmed@google.com> Cc: Yu Zhao <yuzhao@google.com> Cc: Jonathan Corbet <corbet@lwn.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> --- .../sysfs-kernel-mm-transparent-hugepage | 18 ++++++++++++ Documentation/admin-guide/mm/transhuge.rst | 28 +++++++++++++++++++ 2 files changed, 46 insertions(+) create mode 100644 Documentation/ABI/testing/sysfs-kernel-mm-transparent-hugepage diff --git a/Documentation/ABI/testing/sysfs-kernel-mm-transparent-hugepage b/Documentation/ABI/testing/sysfs-kernel-mm-transparent-hugepage new file mode 100644 index 0000000000000..7bfbb9cc2c113 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-kernel-mm-transparent-hugepage @@ -0,0 +1,18 @@ +What: /sys/kernel/mm/transparent_hugepage/ +Date: April 2024 +Contact: Linux memory management mailing list <linux-mm@kvack.org> +Description: + /sys/kernel/mm/transparent_hugepage/ contains a number of files and + subdirectories, + + - defrag + - enabled + - hpage_pmd_size + - khugepaged + - shmem_enabled + - use_zero_page + - subdirectories of the form hugepages-<size>kB, where <size> + is the page size of the hugepages supported by the kernel/CPU + combination. + + See Documentation/admin-guide/mm/transhuge.rst for details. diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst index 04eb45a2f9406..e0fe17affeb3f 100644 --- a/Documentation/admin-guide/mm/transhuge.rst +++ b/Documentation/admin-guide/mm/transhuge.rst @@ -447,6 +447,34 @@ thp_swpout_fallback Usually because failed to allocate some continuous swap space for the huge page. +In /sys/kernel/mm/transparent_hugepage/hugepages-<size>kB/stats, There are +also individual counters for each huge page size, which can be utilized to +monitor the system's effectiveness in providing huge pages for usage. Each +counter has its own corresponding file. + +anon_fault_alloc + is incremented every time a huge page is successfully + allocated and charged to handle a page fault. + +anon_fault_fallback + is incremented if a page fault fails to allocate or charge + a huge page and instead falls back to using huge pages with + lower orders or small pages. + +anon_fault_fallback_charge + is incremented if a page fault fails to charge a huge page and + instead falls back to using huge pages with lower orders or + small pages even though the allocation was successful. + +anon_swpout + is incremented every time a huge page is swapped out in one + piece without splitting. + +anon_swpout_fallback + is incremented if a huge page has to be split before swapout. + Usually because failed to allocate some continuous swap space + for the huge page. + 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 -- GitLab