tools/mm: add thpmaps script to dump THP usage info

With the proliferation of large folios for file-backed memory, and more
recently the introduction of multi-size THP for anonymous memory, it is
becoming useful to be able to see exactly how large folios are mapped into
processes.  For some architectures (e.g.  arm64), if most memory is mapped
using contpte-sized and -aligned blocks, TLB usage can be optimized so
it's useful to see where these requirements are and are not being met.

thpmaps is a Python utility that reads /proc/<pid>/smaps,
/proc/<pid>/pagemap and /proc/kpageflags to print information about how
transparent huge pages (both file and anon) are mapped to a specified
process or cgroup.  It aims to help users debug and optimize their
workloads.  In future we may wish to introduce stats directly into the
kernel (e.g.  smaps or similar), but for now this provides a short term
solution without the need to introduce any new ABI.

Run with help option for a full listing of the arguments:

    # ./thpmaps --help

--8<--
usage: thpmaps [-h] [--pid pid | --cgroup path] [--rollup]
               [--cont size[KMG]] [--inc-smaps] [--inc-empty]
               [--periodic sleep_ms]

Prints information about how transparent huge pages are mapped, either
system-wide, or for a specified process or cgroup.

When run with --pid, the user explicitly specifies the set of pids to
scan.  e.g.  "--pid 10 [--pid 134 ...]".  When run with --cgroup, the user
passes either a v1 or v2 cgroup and all pids that belong to the cgroup
subtree are scanned.  When run with neither --pid nor --cgroup, the full
set of pids on the system is gathered from /proc and scanned as if the
user had provided "--pid 1 --pid 2 ...".

A default set of statistics is always generated for THP mappings. 
However, it is also possible to generate additional statistics for
"contiguous block mappings" where the block size is user-defined.

Statistics are maintained independently for anonymous and file-backed
(pagecache) memory and are shown both in kB and as a percentage of either
total anonymous or total file-backed memory as appropriate.

THP Statistics
--------------

Statistics are always generated for fully- and contiguously-mapped THPs
whose mapping address is aligned to their size, for each <size> supported
by the system.  Separate counters describe THPs mapped by PTE vs those
mapped by PMD.  (Although note a THP can only be mapped by PMD if it is
PMD-sized):

- anon-thp-pte-aligned-<size>kB
- file-thp-pte-aligned-<size>kB
- anon-thp-pmd-aligned-<size>kB
- file-thp-pmd-aligned-<size>kB

Similarly, statistics are always generated for fully- and contiguously-
mapped THPs whose mapping address is *not* aligned to their size, for each
<size> supported by the system.  Due to the unaligned mapping, it is
impossible to map by PMD, so there are only PTE counters for this case:

- anon-thp-pte-unaligned-<size>kB
- file-thp-pte-unaligned-<size>kB

Statistics are also always generated for mapped pages that belong to a THP
but where the is THP is *not* fully- and contiguously- mapped.  These
"partial" mappings are all counted in the same counter regardless of the
size of the THP that is partially mapped:

- anon-thp-pte-partial
- file-thp-pte-partial

Contiguous Block Statistics
---------------------------

An optional, additional set of statistics is generated for every
contiguous block size specified with `--cont <size>`.  These statistics
show how much memory is mapped in contiguous blocks of <size> and also
aligned to <size>.  A given contiguous block must all belong to the same
THP, but there is no requirement for it to be the *whole* THP.  Separate
counters describe contiguous blocks mapped by PTE vs those mapped by PMD:

- anon-cont-pte-aligned-<size>kB
- file-cont-pte-aligned-<size>kB
- anon-cont-pmd-aligned-<size>kB
- file-cont-pmd-aligned-<size>kB

As an example, if monitoring 64K contiguous blocks (--cont 64K), there are
a number of sources that could provide such blocks: a fully- and
contiguously-mapped 64K THP that is aligned to a 64K boundary would
provide 1 block.  A fully- and contiguously-mapped 128K THP that is
aligned to at least a 64K boundary would provide 2 blocks.  Or a 128K THP
that maps its first 100K, but contiguously and starting at a 64K boundary
would provide 1 block.  A fully- and contiguously-mapped 2M THP would
provide 32 blocks.  There are many other possible permutations.

options:
  -h, --help           show this help message and exit
  --pid pid            Process id of the target process. Maybe issued
                       multiple times to scan multiple processes. --pid
                       and --cgroup are mutually exclusive. If neither
                       are provided, all processes are scanned to
                       provide system-wide information.
  --cgroup path        Path to the target cgroup in sysfs. Iterates
                       over every pid in the cgroup and its children.
                       --pid and --cgroup are mutually exclusive. If
                       neither are provided, all processes are scanned
                       to provide system-wide information.
  --rollup             Sum the per-vma statistics to provide a summary
                       over the whole system, process or cgroup.
  --cont size[KMG]     Adds stats for memory that is mapped in
                       contiguous blocks of <size> and also aligned to
                       <size>. May be issued multiple times to track
                       multiple sized blocks. Useful to infer e.g.
                       arm64 contpte and hpa mappings. Size must be a
                       power-of-2 number of pages.
  --inc-smaps          Include all numerical, additive
                       /proc/<pid>/smaps stats in the output.
  --inc-empty          Show all statistics including those whose value
                       is 0.
  --periodic sleep_ms  Run in a loop, polling every sleep_ms
                       milliseconds.

Requires root privilege to access pagemap and kpageflags.
--8<--

Example command to summarise fully and partially mapped THPs and 64K
contiguous blocks over all VMAs in all processes in the system
(--inc-empty forces printing stats that are 0):

    # ./thpmaps --cont 64K --rollup --inc-empty

--8<--
anon-thp-pmd-aligned-2048kB:      139264 kB ( 6%)
file-thp-pmd-aligned-2048kB:           0 kB ( 0%)
anon-thp-pte-aligned-16kB:             0 kB ( 0%)
anon-thp-pte-aligned-32kB:             0 kB ( 0%)
anon-thp-pte-aligned-64kB:         72256 kB ( 3%)
anon-thp-pte-aligned-128kB:            0 kB ( 0%)
anon-thp-pte-aligned-256kB:            0 kB ( 0%)
anon-thp-pte-aligned-512kB:            0 kB ( 0%)
anon-thp-pte-aligned-1024kB:           0 kB ( 0%)
anon-thp-pte-aligned-2048kB:           0 kB ( 0%)
anon-thp-pte-unaligned-16kB:           0 kB ( 0%)
anon-thp-pte-unaligned-32kB:           0 kB ( 0%)
anon-thp-pte-unaligned-64kB:           0 kB ( 0%)
anon-thp-pte-unaligned-128kB:          0 kB ( 0%)
anon-thp-pte-unaligned-256kB:          0 kB ( 0%)
anon-thp-pte-unaligned-512kB:          0 kB ( 0%)
anon-thp-pte-unaligned-1024kB:         0 kB ( 0%)
anon-thp-pte-unaligned-2048kB:         0 kB ( 0%)
anon-thp-pte-partial:              63232 kB ( 3%)
file-thp-pte-aligned-16kB:        809024 kB (47%)
file-thp-pte-aligned-32kB:         43168 kB ( 3%)
file-thp-pte-aligned-64kB:         98496 kB ( 6%)
file-thp-pte-aligned-128kB:        17536 kB ( 1%)
file-thp-pte-aligned-256kB:            0 kB ( 0%)
file-thp-pte-aligned-512kB:            0 kB ( 0%)
file-thp-pte-aligned-1024kB:           0 kB ( 0%)
file-thp-pte-aligned-2048kB:           0 kB ( 0%)
file-thp-pte-unaligned-16kB:       21712 kB ( 1%)
file-thp-pte-unaligned-32kB:         704 kB ( 0%)
file-thp-pte-unaligned-64kB:         896 kB ( 0%)
file-thp-pte-unaligned-128kB:      44928 kB ( 3%)
file-thp-pte-unaligned-256kB:          0 kB ( 0%)
file-thp-pte-unaligned-512kB:          0 kB ( 0%)
file-thp-pte-unaligned-1024kB:         0 kB ( 0%)
file-thp-pte-unaligned-2048kB:         0 kB ( 0%)
file-thp-pte-partial:               9252 kB ( 1%)
anon-cont-pmd-aligned-64kB:       139264 kB ( 6%)
file-cont-pmd-aligned-64kB:            0 kB ( 0%)
anon-cont-pte-aligned-64kB:       100672 kB ( 4%)
file-cont-pte-aligned-64kB:       161856 kB ( 9%)
--8<--

Link: https://lkml.kernel.org/r/20240116141235.960842-1-ryan.roberts@arm.comSigned-off-by: Ryan Roberts <ryan.roberts@arm.com>
Tested-by: Barry Song <v-songbaohua@oppo.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: William Kucharski <william.kucharski@oracle.com>
Cc: Zenghui Yu <yuzenghui@huawei.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

tools/mm/Makefile

@@ -3,7 +3,8 @@
 #
 include ../scripts/Makefile.include
 
-TARGETS=page-types slabinfo page_owner_sort
+BUILD_TARGETS=page-types slabinfo page_owner_sort
+INSTALL_TARGETS = $(BUILD_TARGETS) thpmaps
 
 LIB_DIR = ../lib/api
 LIBS = $(LIB_DIR)/libapi.a
@@ -11,9 +12,9 @@ LIBS = $(LIB_DIR)/libapi.a
 CFLAGS += -Wall -Wextra -I../lib/ -pthread
 LDFLAGS += $(LIBS) -pthread
 
-all: $(TARGETS)
+all: $(BUILD_TARGETS)
 
-$(TARGETS): $(LIBS)
+$(BUILD_TARGETS): $(LIBS)
 
 $(LIBS):
 	make -C $(LIB_DIR)
@@ -29,4 +30,4 @@ sbindir ?= /usr/sbin
 
 install: all
 	install -d $(DESTDIR)$(sbindir)
-	install -m 755 -p $(TARGETS) $(DESTDIR)$(sbindir)
+	install -m 755 -p $(INSTALL_TARGETS) $(DESTDIR)$(sbindir)

tools/mm/thpmaps

+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0-only
+# Copyright (C) 2024 ARM Ltd.
+#
+# Utility providing smaps-like output detailing transparent hugepage usage.
+# For more info, run:
+# ./thpmaps --help
+#
+# Requires numpy:
+# pip3 install numpy
+
+
+import argparse
+import collections
+import math
+import os
+import re
+import resource
+import shutil
+import sys
+import textwrap
+import time
+import numpy as np
+
+
+with open('/sys/kernel/mm/transparent_hugepage/hpage_pmd_size') as f:
+    PAGE_SIZE = resource.getpagesize()
+    PAGE_SHIFT = int(math.log2(PAGE_SIZE))
+    PMD_SIZE = int(f.read())
+    PMD_ORDER = int(math.log2(PMD_SIZE / PAGE_SIZE))
+
+
+def align_forward(v, a):
+    return (v + (a - 1)) & ~(a - 1)
+
+
+def align_offset(v, a):
+    return v & (a - 1)
+
+
+def kbnr(kb):
+    # Convert KB to number of pages.
+    return (kb << 10) >> PAGE_SHIFT
+
+
+def nrkb(nr):
+    # Convert number of pages to KB.
+    return (nr << PAGE_SHIFT) >> 10
+
+
+def odkb(order):
+    # Convert page order to KB.
+    return (PAGE_SIZE << order) >> 10
+
+
+def cont_ranges_all(search, index):
+    # Given a list of arrays, find the ranges for which values are monotonically
+    # incrementing in all arrays. all arrays in search and index must be the
+    # same size.
+    sz = len(search[0])
+    r = np.full(sz, 2)
+    d = np.diff(search[0]) == 1
+    for dd in [np.diff(arr) == 1 for arr in search[1:]]:
+        d &= dd
+    r[1:] -= d
+    r[:-1] -= d
+    return [np.repeat(arr, r).reshape(-1, 2) for arr in index]
+
+
+class ArgException(Exception):
+    pass
+
+
+class FileIOException(Exception):
+    pass
+
+
+class BinArrayFile:
+    # Base class used to read /proc/<pid>/pagemap and /proc/kpageflags into a
+    # numpy array. Use inherrited class in a with clause to ensure file is
+    # closed when it goes out of scope.
+    def __init__(self, filename, element_size):
+        self.element_size = element_size
+        self.filename = filename
+        self.fd = os.open(self.filename, os.O_RDONLY)
+
+    def cleanup(self):
+        os.close(self.fd)
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        self.cleanup()
+
+    def _readin(self, offset, buffer):
+        length = os.preadv(self.fd, (buffer,), offset)
+        if len(buffer) != length:
+            raise FileIOException('error: {} failed to read {} bytes at {:x}'
+                            .format(self.filename, len(buffer), offset))
+
+    def _toarray(self, buf):
+        assert(self.element_size == 8)
+        return np.frombuffer(buf, dtype=np.uint64)
+
+    def getv(self, vec):
+        vec *= self.element_size
+        offsets = vec[:, 0]
+        lengths = (np.diff(vec) + self.element_size).reshape(len(vec))
+        buf = bytearray(int(np.sum(lengths)))
+        view = memoryview(buf)
+        pos = 0
+        for offset, length in zip(offsets, lengths):
+            offset = int(offset)
+            length = int(length)
+            self._readin(offset, view[pos:pos+length])
+            pos += length
+        return self._toarray(buf)
+
+    def get(self, index, nr=1):
+        offset = index * self.element_size
+        length = nr * self.element_size
+        buf = bytearray(length)
+        self._readin(offset, buf)
+        return self._toarray(buf)
+
+
+PM_PAGE_PRESENT = 1 << 63
+PM_PFN_MASK = (1 << 55) - 1
+
+class PageMap(BinArrayFile):
+    # Read ranges of a given pid's pagemap into a numpy array.
+    def __init__(self, pid='self'):
+        super().__init__(f'/proc/{pid}/pagemap', 8)
+
+
+KPF_ANON = 1 << 12
+KPF_COMPOUND_HEAD = 1 << 15
+KPF_COMPOUND_TAIL = 1 << 16
+KPF_THP = 1 << 22
+
+class KPageFlags(BinArrayFile):
+    # Read ranges of /proc/kpageflags into a numpy array.
+    def __init__(self):
+         super().__init__(f'/proc/kpageflags', 8)
+
+
+vma_all_stats = set([
+    "Size",
+    "Rss",
+    "Pss",
+    "Pss_Dirty",
+    "Shared_Clean",
+    "Shared_Dirty",
+    "Private_Clean",
+    "Private_Dirty",
+    "Referenced",
+    "Anonymous",
+    "KSM",
+    "LazyFree",
+    "AnonHugePages",
+    "ShmemPmdMapped",
+    "FilePmdMapped",
+    "Shared_Hugetlb",
+    "Private_Hugetlb",
+    "Swap",
+    "SwapPss",
+    "Locked",
+])
+
+vma_min_stats = set([
+    "Rss",
+    "Anonymous",
+    "AnonHugePages",
+    "ShmemPmdMapped",
+    "FilePmdMapped",
+])
+
+VMA = collections.namedtuple('VMA', [
+    'name',
+    'start',
+    'end',
+    'read',
+    'write',
+    'execute',
+    'private',
+    'pgoff',
+    'major',
+    'minor',
+    'inode',
+    'stats',
+])
+
+class VMAList:
+    # A container for VMAs, parsed from /proc/<pid>/smaps. Iterate over the
+    # instance to receive VMAs.
+    def __init__(self, pid='self', stats=[]):
+        self.vmas = []
+        with open(f'/proc/{pid}/smaps', 'r') as file:
+            for line in file:
+                elements = line.split()
+                if '-' in elements[0]:
+                    start, end = map(lambda x: int(x, 16), elements[0].split('-'))
+                    major, minor = map(lambda x: int(x, 16), elements[3].split(':'))
+                    self.vmas.append(VMA(
+                        name=elements[5] if len(elements) == 6 else '',
+                        start=start,
+                        end=end,
+                        read=elements[1][0] == 'r',
+                        write=elements[1][1] == 'w',
+                        execute=elements[1][2] == 'x',
+                        private=elements[1][3] == 'p',
+                        pgoff=int(elements[2], 16),
+                        major=major,
+                        minor=minor,
+                        inode=int(elements[4], 16),
+                        stats={},
+                    ))
+                else:
+                    param = elements[0][:-1]
+                    if param in stats:
+                        value = int(elements[1])
+                        self.vmas[-1].stats[param] = {'type': None, 'value': value}
+
+    def __iter__(self):
+        yield from self.vmas
+
+
+def thp_parse(vma, kpageflags, ranges, indexes, vfns, pfns, anons, heads):
+    # Given 4 same-sized arrays representing a range within a page table backed
+    # by THPs (vfns: virtual frame numbers, pfns: physical frame numbers, anons:
+    # True if page is anonymous, heads: True if page is head of a THP), return a
+    # dictionary of statistics describing the mapped THPs.
+    stats = {
+        'file': {
+            'partial': 0,
+            'aligned': [0] * (PMD_ORDER + 1),
+            'unaligned': [0] * (PMD_ORDER + 1),
+        },
+        'anon': {
+            'partial': 0,
+            'aligned': [0] * (PMD_ORDER + 1),
+            'unaligned': [0] * (PMD_ORDER + 1),
+        },
+    }
+
+    for rindex, rpfn in zip(ranges[0], ranges[2]):
+        index_next = int(rindex[0])
+        index_end = int(rindex[1]) + 1
+        pfn_end = int(rpfn[1]) + 1
+
+        folios = indexes[index_next:index_end][heads[index_next:index_end]]
+
+        # Account pages for any partially mapped THP at the front. In that case,
+        # the first page of the range is a tail.
+        nr = (int(folios[0]) if len(folios) else index_end) - index_next
+        stats['anon' if anons[index_next] else 'file']['partial'] += nr
+
+        # Account pages for any partially mapped THP at the back. In that case,
+        # the next page after the range is a tail.
+        if len(folios):
+            flags = int(kpageflags.get(pfn_end)[0])
+            if flags & KPF_COMPOUND_TAIL:
+                nr = index_end - int(folios[-1])
+                folios = folios[:-1]
+                index_end -= nr
+                stats['anon' if anons[index_end - 1] else 'file']['partial'] += nr
+
+        # Account fully mapped THPs in the middle of the range.
+        if len(folios):
+            folio_nrs = np.append(np.diff(folios), np.uint64(index_end - folios[-1]))
+            folio_orders = np.log2(folio_nrs).astype(np.uint64)
+            for index, order in zip(folios, folio_orders):
+                index = int(index)
+                order = int(order)
+                nr = 1 << order
+                vfn = int(vfns[index])
+                align = 'aligned' if align_forward(vfn, nr) == vfn else 'unaligned'
+                anon = 'anon' if anons[index] else 'file'
+                stats[anon][align][order] += nr
+
+    # Account PMD-mapped THPs spearately, so filter out of the stats. There is a
+    # race between acquiring the smaps stats and reading pagemap, where memory
+    # could be deallocated. So clamp to zero incase it would have gone negative.
+    anon_pmd_mapped = vma.stats['AnonHugePages']['value']
+    file_pmd_mapped = vma.stats['ShmemPmdMapped']['value'] + \
+                      vma.stats['FilePmdMapped']['value']
+    stats['anon']['aligned'][PMD_ORDER] = max(0, stats['anon']['aligned'][PMD_ORDER] - kbnr(anon_pmd_mapped))
+    stats['file']['aligned'][PMD_ORDER] = max(0, stats['file']['aligned'][PMD_ORDER] - kbnr(file_pmd_mapped))
+
+    rstats = {
+        f"anon-thp-pmd-aligned-{odkb(PMD_ORDER)}kB": {'type': 'anon', 'value': anon_pmd_mapped},
+        f"file-thp-pmd-aligned-{odkb(PMD_ORDER)}kB": {'type': 'file', 'value': file_pmd_mapped},
+    }
+
+    def flatten_sub(type, subtype, stats):
+        param = f"{type}-thp-pte-{subtype}-{{}}kB"
+        for od, nr in enumerate(stats[2:], 2):
+            rstats[param.format(odkb(od))] = {'type': type, 'value': nrkb(nr)}
+
+    def flatten_type(type, stats):
+        flatten_sub(type, 'aligned', stats['aligned'])
+        flatten_sub(type, 'unaligned', stats['unaligned'])
+        rstats[f"{type}-thp-pte-partial"] = {'type': type, 'value': nrkb(stats['partial'])}
+
+    flatten_type('anon', stats['anon'])
+    flatten_type('file', stats['file'])
+
+    return rstats
+
+
+def cont_parse(vma, order, ranges, anons, heads):
+    # Given 4 same-sized arrays representing a range within a page table backed
+    # by THPs (vfns: virtual frame numbers, pfns: physical frame numbers, anons:
+    # True if page is anonymous, heads: True if page is head of a THP), return a
+    # dictionary of statistics describing the contiguous blocks.
+    nr_cont = 1 << order
+    nr_anon = 0
+    nr_file = 0
+
+    for rindex, rvfn, rpfn in zip(*ranges):
+        index_next = int(rindex[0])
+        index_end = int(rindex[1]) + 1
+        vfn_start = int(rvfn[0])
+        pfn_start = int(rpfn[0])
+
+        if align_offset(pfn_start, nr_cont) != align_offset(vfn_start, nr_cont):
+            continue
+
+        off = align_forward(vfn_start, nr_cont) - vfn_start
+        index_next += off
+
+        while index_next + nr_cont <= index_end:
+            folio_boundary = heads[index_next+1:index_next+nr_cont].any()
+            if not folio_boundary:
+                if anons[index_next]:
+                    nr_anon += nr_cont
+                else:
+                    nr_file += nr_cont
+            index_next += nr_cont
+
+    # Account blocks that are PMD-mapped spearately, so filter out of the stats.
+    # There is a race between acquiring the smaps stats and reading pagemap,
+    # where memory could be deallocated. So clamp to zero incase it would have
+    # gone negative.
+    anon_pmd_mapped = vma.stats['AnonHugePages']['value']
+    file_pmd_mapped = vma.stats['ShmemPmdMapped']['value'] + \
+                    vma.stats['FilePmdMapped']['value']
+    nr_anon = max(0, nr_anon - kbnr(anon_pmd_mapped))
+    nr_file = max(0, nr_file - kbnr(file_pmd_mapped))
+
+    rstats = {
+        f"anon-cont-pmd-aligned-{nrkb(nr_cont)}kB": {'type': 'anon', 'value': anon_pmd_mapped},
+        f"file-cont-pmd-aligned-{nrkb(nr_cont)}kB": {'type': 'file', 'value': file_pmd_mapped},
+    }
+
+    rstats[f"anon-cont-pte-aligned-{nrkb(nr_cont)}kB"] = {'type': 'anon', 'value': nrkb(nr_anon)}
+    rstats[f"file-cont-pte-aligned-{nrkb(nr_cont)}kB"] = {'type': 'file', 'value': nrkb(nr_file)}
+
+    return rstats
+
+
+def vma_print(vma, pid):
+    # Prints a VMA instance in a format similar to smaps. The main difference is
+    # that the pid is included as the first value.
+    print("{:010d}: {:016x}-{:016x} {}{}{}{} {:08x} {:02x}:{:02x} {:08x} {}"
+        .format(
+            pid, vma.start, vma.end,
+            'r' if vma.read else '-', 'w' if vma.write else '-',
+            'x' if vma.execute else '-', 'p' if vma.private else 's',
+            vma.pgoff, vma.major, vma.minor, vma.inode, vma.name
+        ))
+
+
+def stats_print(stats, tot_anon, tot_file, inc_empty):
+    # Print a statistics dictionary.
+    label_field = 32
+    for label, stat in stats.items():
+        type = stat['type']
+        value = stat['value']
+        if value or inc_empty:
+            pad = max(0, label_field - len(label) - 1)
+            if type == 'anon' and tot_anon > 0:
+                percent = f' ({value / tot_anon:3.0%})'
+            elif type == 'file' and tot_file > 0:
+                percent = f' ({value / tot_file:3.0%})'
+            else:
+                percent = ''
+            print(f"{label}:{' ' * pad}{value:8} kB{percent}")
+
+
+def vma_parse(vma, pagemap, kpageflags, contorders):
+    # Generate thp and cont statistics for a single VMA.
+    start = vma.start >> PAGE_SHIFT
+    end = vma.end >> PAGE_SHIFT
+
+    pmes = pagemap.get(start, end - start)
+    present = pmes & PM_PAGE_PRESENT != 0
+    pfns = pmes & PM_PFN_MASK
+    pfns = pfns[present]
+    vfns = np.arange(start, end, dtype=np.uint64)
+    vfns = vfns[present]
+
+    pfn_vec = cont_ranges_all([pfns], [pfns])[0]
+    flags = kpageflags.getv(pfn_vec)
+    anons = flags & KPF_ANON != 0
+    heads = flags & KPF_COMPOUND_HEAD != 0
+    thps = flags & KPF_THP != 0
+
+    vfns = vfns[thps]
+    pfns = pfns[thps]
+    anons = anons[thps]
+    heads = heads[thps]
+
+    indexes = np.arange(len(vfns), dtype=np.uint64)
+    ranges = cont_ranges_all([vfns, pfns], [indexes, vfns, pfns])
+
+    thpstats = thp_parse(vma, kpageflags, ranges, indexes, vfns, pfns, anons, heads)
+    contstats = [cont_parse(vma, order, ranges, anons, heads) for order in contorders]
+
+    tot_anon = vma.stats['Anonymous']['value']
+    tot_file = vma.stats['Rss']['value'] - tot_anon
+
+    return {
+        **thpstats,
+        **{k: v for s in contstats for k, v in s.items()}
+    }, tot_anon, tot_file
+
+
+def do_main(args):
+    pids = set()
+    rollup = {}
+    rollup_anon = 0
+    rollup_file = 0
+
+    if args.cgroup:
+        strict = False
+        for walk_info in os.walk(args.cgroup):
+            cgroup = walk_info[0]
+            with open(f'{cgroup}/cgroup.procs') as pidfile:
+                for line in pidfile.readlines():
+                    pids.add(int(line.strip()))
+    elif args.pid:
+        strict = True
+        pids = pids.union(args.pid)
+    else:
+        strict = False
+        for pid in os.listdir('/proc'):
+            if pid.isdigit():
+                pids.add(int(pid))
+
+    if not args.rollup:
+        print("       PID             START              END PROT   OFFSET   DEV    INODE OBJECT")
+
+    for pid in pids:
+        try:
+            with PageMap(pid) as pagemap:
+                with KPageFlags() as kpageflags:
+                    for vma in VMAList(pid, vma_all_stats if args.inc_smaps else vma_min_stats):
+                        if (vma.read or vma.write or vma.execute) and vma.stats['Rss']['value'] > 0:
+                            stats, vma_anon, vma_file = vma_parse(vma, pagemap, kpageflags, args.cont)
+                        else:
+                            stats = {}
+                            vma_anon = 0
+                            vma_file = 0
+                        if args.inc_smaps:
+                            stats = {**vma.stats, **stats}
+                        if args.rollup:
+                            for k, v in stats.items():
+                                if k in rollup:
+                                    assert(rollup[k]['type'] == v['type'])
+                                    rollup[k]['value'] += v['value']
+                                else:
+                                    rollup[k] = v
+                            rollup_anon += vma_anon
+                            rollup_file += vma_file
+                        else:
+                            vma_print(vma, pid)
+                            stats_print(stats, vma_anon, vma_file, args.inc_empty)
+        except (FileNotFoundError, ProcessLookupError, FileIOException):
+            if strict:
+                raise
+
+    if args.rollup:
+        stats_print(rollup, rollup_anon, rollup_file, args.inc_empty)
+
+
+def main():
+    docs_width = shutil.get_terminal_size().columns
+    docs_width -= 2
+    docs_width = min(80, docs_width)
+
+    def format(string):
+        text = re.sub(r'\s+', ' ', string)
+        text = re.sub(r'\s*\\n\s*', '\n', text)
+        paras = text.split('\n')
+        paras = [textwrap.fill(p, width=docs_width) for p in paras]
+        return '\n'.join(paras)
+
+    def formatter(prog):
+        return argparse.RawDescriptionHelpFormatter(prog, width=docs_width)
+
+    def size2order(human):
+        units = {
+            "K": 2**10, "M": 2**20, "G": 2**30,
+            "k": 2**10, "m": 2**20, "g": 2**30,
+        }
+        unit = 1
+        if human[-1] in units:
+            unit = units[human[-1]]
+            human = human[:-1]
+        try:
+            size = int(human)
+        except ValueError:
+            raise ArgException('error: --cont value must be integer size with optional KMG unit')
+        size *= unit
+        order = int(math.log2(size / PAGE_SIZE))
+        if order < 1:
+            raise ArgException('error: --cont value must be size of at least 2 pages')
+        if (1 << order) * PAGE_SIZE != size:
+            raise ArgException('error: --cont value must be size of power-of-2 pages')
+        if order > PMD_ORDER:
+            raise ArgException('error: --cont value must be less than or equal to PMD order')
+        return order
+
+    parser = argparse.ArgumentParser(formatter_class=formatter,
+        description=format("""Prints information about how transparent huge
+                    pages are mapped, either system-wide, or for a specified
+                    process or cgroup.\\n
+                    \\n
+                    When run with --pid, the user explicitly specifies the set
+                    of pids to scan. e.g. "--pid 10 [--pid 134 ...]". When run
+                    with --cgroup, the user passes either a v1 or v2 cgroup and
+                    all pids that belong to the cgroup subtree are scanned. When
+                    run with neither --pid nor --cgroup, the full set of pids on
+                    the system is gathered from /proc and scanned as if the user
+                    had provided "--pid 1 --pid 2 ...".\\n
+                    \\n
+                    A default set of statistics is always generated for THP
+                    mappings. However, it is also possible to generate
+                    additional statistics for "contiguous block mappings" where
+                    the block size is user-defined.\\n
+                    \\n
+                    Statistics are maintained independently for anonymous and
+                    file-backed (pagecache) memory and are shown both in kB and
+                    as a percentage of either total anonymous or total
+                    file-backed memory as appropriate.\\n
+                    \\n
+                    THP Statistics\\n
+                    --------------\\n
+                    \\n
+                    Statistics are always generated for fully- and
+                    contiguously-mapped THPs whose mapping address is aligned to
+                    their size, for each <size> supported by the system.
+                    Separate counters describe THPs mapped by PTE vs those
+                    mapped by PMD. (Although note a THP can only be mapped by
+                    PMD if it is PMD-sized):\\n
+                    \\n
+                    - anon-thp-pte-aligned-<size>kB\\n
+                    - file-thp-pte-aligned-<size>kB\\n
+                    - anon-thp-pmd-aligned-<size>kB\\n
+                    - file-thp-pmd-aligned-<size>kB\\n
+                    \\n
+                    Similarly, statistics are always generated for fully- and
+                    contiguously-mapped THPs whose mapping address is *not*
+                    aligned to their size, for each <size> supported by the
+                    system. Due to the unaligned mapping, it is impossible to
+                    map by PMD, so there are only PTE counters for this case:\\n
+                    \\n
+                    - anon-thp-pte-unaligned-<size>kB\\n
+                    - file-thp-pte-unaligned-<size>kB\\n
+                    \\n
+                    Statistics are also always generated for mapped pages that
+                    belong to a THP but where the is THP is *not* fully- and
+                    contiguously- mapped. These "partial" mappings are all
+                    counted in the same counter regardless of the size of the
+                    THP that is partially mapped:\\n
+                    \\n
+                    - anon-thp-pte-partial\\n
+                    - file-thp-pte-partial\\n
+                    \\n
+                    Contiguous Block Statistics\\n
+                    ---------------------------\\n
+                    \\n
+                    An optional, additional set of statistics is generated for
+                    every contiguous block size specified with `--cont <size>`.
+                    These statistics show how much memory is mapped in
+                    contiguous blocks of <size> and also aligned to <size>. A
+                    given contiguous block must all belong to the same THP, but
+                    there is no requirement for it to be the *whole* THP.
+                    Separate counters describe contiguous blocks mapped by PTE
+                    vs those mapped by PMD:\\n
+                    \\n
+                    - anon-cont-pte-aligned-<size>kB\\n
+                    - file-cont-pte-aligned-<size>kB\\n
+                    - anon-cont-pmd-aligned-<size>kB\\n
+                    - file-cont-pmd-aligned-<size>kB\\n
+                    \\n
+                    As an example, if monitoring 64K contiguous blocks (--cont
+                    64K), there are a number of sources that could provide such
+                    blocks: a fully- and contiguously-mapped 64K THP that is
+                    aligned to a 64K boundary would provide 1 block. A fully-
+                    and contiguously-mapped 128K THP that is aligned to at least
+                    a 64K boundary would provide 2 blocks. Or a 128K THP that
+                    maps its first 100K, but contiguously and starting at a 64K
+                    boundary would provide 1 block. A fully- and
+                    contiguously-mapped 2M THP would provide 32 blocks. There
+                    are many other possible permutations.\\n"""),
+        epilog=format("""Requires root privilege to access pagemap and
+                    kpageflags."""))
+
+    group = parser.add_mutually_exclusive_group(required=False)
+    group.add_argument('--pid',
+        metavar='pid', required=False, type=int, default=[], action='append',
+        help="""Process id of the target process. Maybe issued multiple times to
+            scan multiple processes. --pid and --cgroup are mutually exclusive.
+            If neither are provided, all processes are scanned to provide
+            system-wide information.""")
+
+    group.add_argument('--cgroup',
+        metavar='path', required=False,
+        help="""Path to the target cgroup in sysfs. Iterates over every pid in
+            the cgroup and its children. --pid and --cgroup are mutually
+            exclusive. If neither are provided, all processes are scanned to
+            provide system-wide information.""")
+
+    parser.add_argument('--rollup',
+        required=False, default=False, action='store_true',
+        help="""Sum the per-vma statistics to provide a summary over the whole
+            system, process or cgroup.""")
+
+    parser.add_argument('--cont',
+        metavar='size[KMG]', required=False, default=[], action='append',
+        help="""Adds stats for memory that is mapped in contiguous blocks of
+            <size> and also aligned to <size>. May be issued multiple times to
+            track multiple sized blocks. Useful to infer e.g. arm64 contpte and
+            hpa mappings. Size must be a power-of-2 number of pages.""")
+
+    parser.add_argument('--inc-smaps',
+        required=False, default=False, action='store_true',
+        help="""Include all numerical, additive /proc/<pid>/smaps stats in the
+            output.""")
+
+    parser.add_argument('--inc-empty',
+        required=False, default=False, action='store_true',
+        help="""Show all statistics including those whose value is 0.""")
+
+    parser.add_argument('--periodic',
+        metavar='sleep_ms', required=False, type=int,
+        help="""Run in a loop, polling every sleep_ms milliseconds.""")
+
+    args = parser.parse_args()
+
+    try:
+        args.cont = [size2order(cont) for cont in args.cont]
+    except ArgException as e:
+        parser.print_usage()
+        raise
+
+    if args.periodic:
+        while True:
+            do_main(args)
+            print()
+            time.sleep(args.periodic / 1000)
+    else:
+        do_main(args)
+
+
+if __name__ == "__main__":
+    try:
+        main()
+    except Exception as e:
+        prog = os.path.basename(sys.argv[0])
+        print(f'{prog}: {e}')
+        exit(1)