From 478fd0d8ec1286cb03cf8ebf6beed46746775c9e Mon Sep 17 00:00:00 2001 From: David Hildenbrand Date: Fri, 7 Jun 2024 14:23:57 +0200 Subject: 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 Cc: Alexey Dobriyan Cc: Jonathan Corbet Cc: Kirill A. Shutemov Cc: Lance Yang Cc: Oscar Salvador Signed-off-by: Andrew Morton --- Documentation/admin-guide/mm/pagemap.rst | 21 --------------------- 1 file changed, 21 deletions(-) (limited to 'Documentation') 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 ============================ -- cgit v1.2.3