admin-guide/mm/pagemap.rst

12    physical frame each virtual page is mapped to.  It contains one 64-bit
16     * Bits 0-54  page frame number (PFN) if present
17     * Bits 0-4   swap type if swapped
18     * Bits 5-54  swap offset if swapped
19     * Bit  55    pte is soft-dirty (see
20       Documentation/admin-guide/mm/soft-dirty.rst)
22     * Bit  57    pte is uffd-wp write-protected (since 5.13) (see
23       Documentation/admin-guide/mm/userfaultfd.rst)
24     * Bits 58-60 zero
25     * Bit  61    page is file-page or shared-anon (since 3.5)
26     * Bit  62    page swapped
30    In 4.0 and 4.1 opens by unprivileged fail with -EPERM.  Starting from
31    4.2 the PFN field is zeroed if the user does not have CAP_SYS_ADMIN.
34    If the page is not present but in swap, then the PFN contains an
44  * ``/proc/kpagecount``.  This file contains a 64-bit count of the number of
47 The page-types tool in the tools/mm directory can be used to query the
50  * ``/proc/kpageflags``.  This file contains a 64-bit set of flags for each
83  * ``/proc/kpagecgroup``.  This file contains a 64-bit inode number of the
90 0 - LOCKED
93 7 - SLAB
97 10 - BUDDY
102 15 - COMPOUND_HEAD
106     pages are hugeTLB pages (Documentation/admin-guide/mm/hugetlbpage.rst),
110 16 - COMPOUND_TAIL
112 17 - HUGE
114 19 - HWPOISON
116 20 - NOPAGE
118 21 - KSM
120 22 - THP
122 23 - OFFLINE
124 24 - ZERO_PAGE
126 25 - IDLE
127     The page has not been accessed since it was marked idle (see
128     Documentation/admin-guide/mm/idle_page_tracking.rst).
130     a PTE. To make sure the flag is up-to-date one has to read
132 26 - PGTABLE
136 ---------------------
138 1 - ERROR
140 3 - UPTODATE
141    The page has up-to-date data.
142    ie. for file backed page: (in-memory data revision >= on-disk one)
143 4 - DIRTY
145    i.e. for file backed page: (in-memory data revision >  on-disk one)
146 8 - WRITEBACK
150 ----------------------
152 5 - LRU
154 6 - ACTIVE
156 18 - UNEVICTABLE
157    The page is in the unevictable (non-)LRU list It is somehow pinned and
158    not a candidate for LRU page reclaims, e.g. ramfs pages,
160 2 - REFERENCED
162 9 - RECLAIM
164 11 - MMAP
166 12 - ANON
167    A memory mapped page that is not part of a file.
168 13 - SWAPCACHE
170 14 - SWAPBACKED
173 The page-types tool in the tools/mm directory can be used to query the
184  2. Select the maps you are interested in -- all of them, or a particular
192 memory that a process is using that is not shared with any other process,
201 swapped out. This makes swapped out pages indistinguishable from never-allocated
206 page is swapped out (i.e. SOFT_DIRTY).
208 In user space, whether the page is present, swapped or none can be deduced with
211 lseek() can differentiate between accessed pages (present or swapped out) and
212 holes (none/non-allocated) by specifying the SEEK_DATA flag on the file where
217 cache) and out of memory (swapped out or none/non-allocated).
222 Reading from any of the files will return -EINVAL if you are not starting
223 the read on an 8-byte boundary (e.g., if you sought an odd number of bytes
224 into the file), or if the size of the read is not a multiple of 8 bytes.
226 Before Linux 3.11 pagemap bits 55-60 were used for "page-shift" (which is
228 after first clear of soft-dirty bits. Since Linux 4.2 they are used for