diff options
| author | David Hildenbrand <david@redhat.com> | 2024-06-07 14:23:57 +0200 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2024-07-04 04:30:06 +0200 |
| commit | 478fd0d8ec1286cb03cf8ebf6beed46746775c9e (patch) | |
| tree | c0d1017eee62e6f659e4dba2a61772fcff7379a7 /Documentation | |
| parent | fs/proc: move page_mapcount() to fs/proc/internal.h (diff) | |
| download | linux-478fd0d8ec1286cb03cf8ebf6beed46746775c9e.tar.xz linux-478fd0d8ec1286cb03cf8ebf6beed46746775c9e.zip | |
Documentation/admin-guide/mm/pagemap.rst: drop "Using pagemap to do something useful"
That example was added in 2008. In 2015, we restricted access to the PFNs
in the pagemap to CAP_SYS_ADMIN, making that approach quite less usable.
It's 2024 now, and using that racy and low-lewel mechanism to calculate
the USS should not be considered a good example anymore. /proc/$pid/smaps
and /proc/$pid/smaps_rollup can do a much better job without any of that
low-level handling.
Let's just drop that example.
Link: https://lkml.kernel.org/r/20240607122357.115423-7-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: Oscar Salvador <osalvador@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/admin-guide/mm/pagemap.rst | 21 |
1 files changed, 0 insertions, 21 deletions
diff --git a/Documentation/admin-guide/mm/pagemap.rst b/Documentation/admin-guide/mm/pagemap.rst index f5f065c67615..f2817a801596 100644 --- a/Documentation/admin-guide/mm/pagemap.rst +++ b/Documentation/admin-guide/mm/pagemap.rst @@ -173,27 +173,6 @@ LRU related page flags The page-types tool in the tools/mm directory can be used to query the above flags. -Using pagemap to do something useful -==================================== - -The general procedure for using pagemap to find out about a process' memory -usage goes like this: - - 1. Read ``/proc/pid/maps`` to determine which parts of the memory space are - mapped to what. - 2. Select the maps you are interested in -- all of them, or a particular - library, or the stack or the heap, etc. - 3. Open ``/proc/pid/pagemap`` and seek to the pages you would like to examine. - 4. Read a u64 for each page from pagemap. - 5. Open ``/proc/kpagecount`` and/or ``/proc/kpageflags``. For each PFN you - just read, seek to that entry in the file, and read the data you want. - -For example, to find the "unique set size" (USS), which is the amount of -memory that a process is using that is not shared with any other process, -you can go through every map in the process, find the PFNs, look those up -in kpagecount, and tally up the number of pages that are only referenced -once. - Exceptions for Shared Memory ============================ |