admin-guide/mm/idle_page_tracking.rst

10 The idle page tracking feature allows to track which memory pages are being
13 account when configuring the workload parameters, setting memory cgroup limits,
24 Currently, it consists of the only read-write file,
27 The file implements a bitmap where each bit corresponds to a memory page. The
28 bitmap is represented by an array of 8-byte integers, and the page at PFN #i is
29 mapped to bit #i%64 of array element #i/64, byte order is native. When a bit is
36 the page by writing to the file. A value written to the file is OR-ed with the
39 Only accesses to user memory pages are tracked. These are pages mapped to a
48 -EINVAL if you are not starting the read/write on an 8-byte boundary, or
50 this file beyond max PFN will return -ENXIO.
59     is placed in a memory cgroup.
68 The page-types tool in the tools/vm directory can be used to assist in this.
73 See :ref:`Documentation/admin-guide/mm/pagemap.rst <pagemap>` for more
82 The kernel internally keeps track of accesses to user memory pages in order to
83 reclaim unreferenced pages first on memory shortage conditions. A page is
85 space, in which case one or more PTEs it is mapped to will have the Accessed bit
89  - a userspace process reads or writes a page using a system call (e.g. read(2)
92  - a page that is used for storing filesystem buffers is read or written,
96  - a page is accessed by a device driver using get_user_pages()
98 When a dirty page is written to swap or disk as a result of memory reclaim or
99 exceeding the dirty memory limit, it is not marked referenced.
101 The idle memory tracking feature adds a new page flag, the Idle flag. This flag
108 mapped to, otherwise we will not be able to detect accesses to the page coming
116 Since the idle memory tracking feature is based on the memory reclaimer logic,
118 ignored. That means it will ignore a user memory page if it is isolated, but