[100/131] mm: memcontrol: document the new swap control behavior
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Message ID 20200603230221.FaLLQeEaB%akpm@linux-foundation.org
State New
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  • [001/131] mm/slub: fix a memory leak in sysfs_slab_add()
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Commit Message

Andrew Morton June 3, 2020, 11:02 p.m. UTC
From: Alex Shi <alex.shi@linux.alibaba.com>
Subject: mm: memcontrol: document the new swap control behavior

Link: http://lkml.kernel.org/r/20200508183105.225460-18-hannes@cmpxchg.org
Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 Documentation/admin-guide/cgroup-v1/memory.rst |   19 +++++----------
 1 file changed, 7 insertions(+), 12 deletions(-)

Patch
diff mbox series

--- a/Documentation/admin-guide/cgroup-v1/memory.rst~mm-memcontrol-document-the-new-swap-control-behavior
+++ a/Documentation/admin-guide/cgroup-v1/memory.rst
@@ -199,11 +199,11 @@  An RSS page is unaccounted when it's ful
 unaccounted when it's removed from radix-tree. Even if RSS pages are fully
 unmapped (by kswapd), they may exist as SwapCache in the system until they
 are really freed. Such SwapCaches are also accounted.
-A swapped-in page is not accounted until it's mapped.
+A swapped-in page is accounted after adding into swapcache.
 
 Note: The kernel does swapin-readahead and reads multiple swaps at once.
-This means swapped-in pages may contain pages for other tasks than a task
-causing page fault. So, we avoid accounting at swap-in I/O.
+Since page's memcg recorded into swap whatever memsw enabled, the page will
+be accounted after swapin.
 
 At page migration, accounting information is kept.
 
@@ -222,18 +222,13 @@  the cgroup that brought it in -- this wi
 But see section 8.2: when moving a task to another cgroup, its pages may
 be recharged to the new cgroup, if move_charge_at_immigrate has been chosen.
 
-Exception: If CONFIG_MEMCG_SWAP is not used.
-When you do swapoff and make swapped-out pages of shmem(tmpfs) to
-be backed into memory in force, charges for pages are accounted against the
-caller of swapoff rather than the users of shmem.
-
-2.4 Swap Extension (CONFIG_MEMCG_SWAP)
+2.4 Swap Extension
 --------------------------------------
 
-Swap Extension allows you to record charge for swap. A swapped-in page is
-charged back to original page allocator if possible.
+Swap usage is always recorded for each of cgroup. Swap Extension allows you to
+read and limit it.
 
-When swap is accounted, following files are added.
+When CONFIG_SWAP is enabled, following files are added.
 
  - memory.memsw.usage_in_bytes.
  - memory.memsw.limit_in_bytes.