From: Mike Rapoport <rppt@linux.vnet.ibm.com>
To: Jonathan Corbet <corbet@lwn.net>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>,
Richard Henderson <rth@twiddle.net>,
Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
Matt Turner <mattst88@gmail.com>, Tony Luck <tony.luck@intel.com>,
Fenghua Yu <fenghua.yu@intel.com>,
Ralf Baechle <ralf@linux-mips.org>,
James Hogan <jhogan@kernel.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Alexander Viro <viro@zeniv.linux.org.uk>,
linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
kasan-dev@googlegroups.com, linux-alpha@vger.kernel.org,
linux-ia64@vger.kernel.org, linux-mips@linux-mips.org,
linuxppc-dev@lists.ozlabs.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org, Mike Rapoport <rppt@linux.vnet.ibm.com>
Subject: [PATCH 10/32] docs/vm: idle_page_tracking.txt: convert to ReST format
Date: Wed, 21 Mar 2018 21:22:26 +0200 [thread overview]
Message-ID: <1521660168-14372-11-git-send-email-rppt@linux.vnet.ibm.com> (raw)
In-Reply-To: <1521660168-14372-1-git-send-email-rppt@linux.vnet.ibm.com>
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
---
Documentation/vm/idle_page_tracking.txt | 55 +++++++++++++++++++++------------
1 file changed, 36 insertions(+), 19 deletions(-)
diff --git a/Documentation/vm/idle_page_tracking.txt b/Documentation/vm/idle_page_tracking.txt
index 85dcc3b..9cbe6f8 100644
--- a/Documentation/vm/idle_page_tracking.txt
+++ b/Documentation/vm/idle_page_tracking.txt
@@ -1,4 +1,11 @@
-MOTIVATION
+.. _idle_page_tracking:
+
+==================
+Idle Page Tracking
+==================
+
+Motivation
+==========
The idle page tracking feature allows to track which memory pages are being
accessed by a workload and which are idle. This information can be useful for
@@ -8,10 +15,14 @@ or deciding where to place the workload within a compute cluster.
It is enabled by CONFIG_IDLE_PAGE_TRACKING=y.
-USER API
+.. _user_api:
-The idle page tracking API is located at /sys/kernel/mm/page_idle. Currently,
-it consists of the only read-write file, /sys/kernel/mm/page_idle/bitmap.
+User API
+========
+
+The idle page tracking API is located at ``/sys/kernel/mm/page_idle``.
+Currently, it consists of the only read-write file,
+``/sys/kernel/mm/page_idle/bitmap``.
The file implements a bitmap where each bit corresponds to a memory page. The
bitmap is represented by an array of 8-byte integers, and the page at PFN #i is
@@ -19,8 +30,9 @@ mapped to bit #i%64 of array element #i/64, byte order is native. When a bit is
set, the corresponding page is idle.
A page is considered idle if it has not been accessed since it was marked idle
-(for more details on what "accessed" actually means see the IMPLEMENTATION
-DETAILS section). To mark a page idle one has to set the bit corresponding to
+(for more details on what "accessed" actually means see the :ref:`Implementation
+Details <impl_details>` section).
+To mark a page idle one has to set the bit corresponding to
the page by writing to the file. A value written to the file is OR-ed with the
current bitmap value.
@@ -30,9 +42,9 @@ page types (e.g. SLAB pages) an attempt to mark a page idle is silently ignored,
and hence such pages are never reported idle.
For huge pages the idle flag is set only on the head page, so one has to read
-/proc/kpageflags in order to correctly count idle huge pages.
+``/proc/kpageflags`` in order to correctly count idle huge pages.
-Reading from or writing to /sys/kernel/mm/page_idle/bitmap will return
+Reading from or writing to ``/sys/kernel/mm/page_idle/bitmap`` will return
-EINVAL if you are not starting the read/write on an 8-byte boundary, or
if the size of the read/write is not a multiple of 8 bytes. Writing to
this file beyond max PFN will return -ENXIO.
@@ -41,21 +53,25 @@ That said, in order to estimate the amount of pages that are not used by a
workload one should:
1. Mark all the workload's pages as idle by setting corresponding bits in
- /sys/kernel/mm/page_idle/bitmap. The pages can be found by reading
- /proc/pid/pagemap if the workload is represented by a process, or by
- filtering out alien pages using /proc/kpagecgroup in case the workload is
- placed in a memory cgroup.
+ ``/sys/kernel/mm/page_idle/bitmap``. The pages can be found by reading
+ ``/proc/pid/pagemap`` if the workload is represented by a process, or by
+ filtering out alien pages using ``/proc/kpagecgroup`` in case the workload
+ is placed in a memory cgroup.
2. Wait until the workload accesses its working set.
- 3. Read /sys/kernel/mm/page_idle/bitmap and count the number of bits set. If
- one wants to ignore certain types of pages, e.g. mlocked pages since they
- are not reclaimable, he or she can filter them out using /proc/kpageflags.
+ 3. Read ``/sys/kernel/mm/page_idle/bitmap`` and count the number of bits set.
+ If one wants to ignore certain types of pages, e.g. mlocked pages since they
+ are not reclaimable, he or she can filter them out using
+ ``/proc/kpageflags``.
+
+See Documentation/vm/pagemap.txt for more information about
+``/proc/pid/pagemap``, ``/proc/kpageflags``, and ``/proc/kpagecgroup``.
-See Documentation/vm/pagemap.txt for more information about /proc/pid/pagemap,
-/proc/kpageflags, and /proc/kpagecgroup.
+.. _impl_details:
-IMPLEMENTATION DETAILS
+Implementation Details
+======================
The kernel internally keeps track of accesses to user memory pages in order to
reclaim unreferenced pages first on memory shortage conditions. A page is
@@ -77,7 +93,8 @@ When a dirty page is written to swap or disk as a result of memory reclaim or
exceeding the dirty memory limit, it is not marked referenced.
The idle memory tracking feature adds a new page flag, the Idle flag. This flag
-is set manually, by writing to /sys/kernel/mm/page_idle/bitmap (see the USER API
+is set manually, by writing to ``/sys/kernel/mm/page_idle/bitmap`` (see the
+:ref:`User API <user_api>`
section), and cleared automatically whenever a page is referenced as defined
above.
--
2.7.4
next prev parent reply other threads:[~2018-03-21 19:22 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-21 19:22 [PATCH 00/32] docs/vm: convert to ReST format Mike Rapoport
2018-03-21 19:22 ` [PATCH 01/32] docs/vm: active_mm.txt " Mike Rapoport
2018-03-21 19:22 ` [PATCH 02/32] docs/vm: balance: " Mike Rapoport
2018-03-21 19:22 ` [PATCH 03/32] docs/vm: cleancache.txt: " Mike Rapoport
2018-03-21 19:22 ` [PATCH 04/32] docs/vm: frontswap.txt: " Mike Rapoport
2018-03-21 19:22 ` [PATCH 05/32] docs/vm: highmem.txt: " Mike Rapoport
2018-03-21 19:22 ` [PATCH 06/32] docs/vm: hmm.txt: " Mike Rapoport
2018-03-21 19:22 ` [PATCH 07/32] docs/vm: hugetlbpage.txt: " Mike Rapoport
2018-03-21 19:22 ` [PATCH 08/32] docs/vm: hugetlbfs_reserv.txt: " Mike Rapoport
2018-03-21 19:22 ` [PATCH 09/32] docs/vm: hwpoison.txt: " Mike Rapoport
2018-03-21 19:22 ` Mike Rapoport [this message]
2018-03-21 19:22 ` [PATCH 11/32] docs/vm: ksm.txt: " Mike Rapoport
2018-03-21 19:22 ` [PATCH 12/32] docs/vm: mmu_notifier.txt: " Mike Rapoport
2018-03-21 19:22 ` [PATCH 13/32] docs/vm: numa_memory_policy.txt: " Mike Rapoport
2018-03-21 19:22 ` [PATCH 14/32] docs/vm: overcommit-accounting: " Mike Rapoport
2018-03-21 19:22 ` [PATCH 15/32] docs/vm: page_frags " Mike Rapoport
2018-03-21 19:22 ` [PATCH 16/32] docs/vm: numa: " Mike Rapoport
2018-03-21 19:22 ` [PATCH 17/32] docs/vm: pagemap.txt: " Mike Rapoport
2018-03-21 19:22 ` [PATCH 18/32] docs/vm: page_migration: " Mike Rapoport
2018-03-21 19:22 ` [PATCH 19/32] docs/vm: page_owner: " Mike Rapoport
2018-03-21 19:22 ` [PATCH 20/32] docs/vm: remap_file_pages.txt: conert " Mike Rapoport
2018-03-21 19:22 ` [PATCH 21/32] docs/vm: slub.txt: convert " Mike Rapoport
2018-03-21 19:22 ` [PATCH 22/32] docs/vm: soft-dirty.txt: " Mike Rapoport
2018-03-21 19:22 ` [PATCH 23/32] docs/vm: split_page_table_lock: " Mike Rapoport
2018-03-21 19:22 ` [PATCH 24/32] docs/vm: swap_numa.txt: " Mike Rapoport
2018-03-21 19:22 ` [PATCH 25/32] docs/vm: transhuge.txt: " Mike Rapoport
2018-03-21 19:22 ` [PATCH 26/32] docs/vm: unevictable-lru.txt: " Mike Rapoport
2018-03-21 19:22 ` [PATCH 27/32] docs/vm: userfaultfd.txt: " Mike Rapoport
2018-03-21 19:22 ` [PATCH 28/32] docs/vm: z3fold.txt: " Mike Rapoport
2018-03-21 19:22 ` [PATCH 29/32] docs/vm: zsmalloc.txt: " Mike Rapoport
2018-03-21 19:22 ` [PATCH 30/32] docs/vm: zswap.txt: " Mike Rapoport
2018-03-21 19:22 ` [PATCH 31/32] docs/vm: rename documentation files to .rst Mike Rapoport
2018-03-21 19:22 ` [PATCH 32/32] docs/vm: add index.rst and link MM documentation to top level index Mike Rapoport
2018-03-29 21:46 ` [PATCH 00/32] docs/vm: convert to ReST format Jonathan Corbet
2018-04-01 6:38 ` Mike Rapoport
2018-04-10 10:23 ` Mike Rapoport
2018-04-13 19:55 ` Jonathan Corbet
2018-04-13 20:21 ` Matthew Wilcox
2018-04-15 17:29 ` Mike Rapoport
2018-04-15 17:36 ` Mike Rapoport
2018-04-16 20:35 ` Jonathan Corbet
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