The patch titled
Subject: Documentation: cgroup: add memory.swap.{current,max} description
has been added to the -mm tree. Its filename is
documentation-cgroup-add-memoryswapcurrentmax-description.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/documentation-cgroup-add-memoryswapcurrentmax-description.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/documentation-cgroup-add-memoryswapcurrentmax-description.patch
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------------------------------------------------------
From: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
Subject: Documentation: cgroup: add memory.swap.{current,max} description
The rationale of separate swap counter is given by Johannes Weiner.
Signed-off-by: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/cgroup.txt | 33 +++++++++++++++++++++++++++++++++
1 file changed, 33 insertions(+)
diff -puN Documentation/cgroup.txt~documentation-cgroup-add-memoryswapcurrentmax-description Documentation/cgroup.txt
--- a/Documentation/cgroup.txt~documentation-cgroup-add-memoryswapcurrentmax-description
+++ a/Documentation/cgroup.txt
@@ -819,6 +819,22 @@ PAGE_SIZE multiple when read back.
the cgroup. This may not exactly match the number of
processes killed but should generally be close.
+ memory.swap.current
+
+ A read-only single value file which exists on non-root
+ cgroups.
+
+ The total amount of swap currently being used by the cgroup
+ and its descendants.
+
+ memory.swap.max
+
+ A read-write single value file which exists on non-root
+ cgroups. The default is "max".
+
+ Swap usage hard limit. If a cgroup's swap usage reaches this
+ limit, anonymous meomry of the cgroup will not be swapped out.
+
5-2-2. General Usage
@@ -1291,3 +1307,20 @@ allocation from the slack available in o
system than killing the group. Otherwise, memory.max is there to
limit this type of spillover and ultimately contain buggy or even
malicious applications.
+
+The combined memory+swap accounting and limiting is replaced by real
+control over swap space.
+
+The main argument for a combined memory+swap facility in the original
+cgroup design was that global or parental pressure would always be
+able to swap all anonymous memory of a child group, regardless of the
+child's own (possibly untrusted) configuration. However, untrusted
+groups can sabotage swapping by other means - such as referencing its
+anonymous memory in a tight loop - and an admin can not assume full
+swappability when overcommitting untrusted jobs.
+
+For trusted jobs, on the other hand, a combined counter is not an
+intuitive userspace interface, and it flies in the face of the idea
+that cgroup controllers should account and limit specific physical
+resources. Swap space is a resource like all others in the system,
+and that's why unified hierarchy allows distributing it separately.
_
Patches currently in -mm which might be from vdavydov@xxxxxxxxxxxxx are
revert-kernfs-do-not-account-ino_ida-allocations-to-memcg.patch
revert-gfp-add-__gfp_noaccount.patch
memcg-only-account-kmem-allocations-marked-as-__gfp_account.patch
slab-add-slab_account-flag.patch
vmalloc-allow-to-account-vmalloc-to-memcg.patch
account-certain-kmem-allocations-to-memcg.patch
vmscan-do-not-force-scan-file-lru-if-its-absolute-size-is-small.patch
vmscan-do-not-force-scan-file-lru-if-its-absolute-size-is-small-v2.patch
memcg-do-not-allow-to-disable-tcp-accounting-after-limit-is-set.patch
mm-add-page_check_address_transhuge-helper.patch
mm-add-page_check_address_transhuge-helper-fix.patch
mm-memcontrol-allow-to-disable-kmem-accounting-for-cgroup2.patch
net-drop-tcp_memcontrolc.patch
mm-memcontrol-charge-swap-to-cgroup2.patch
mm-vmscan-pass-memcg-to-get_scan_count.patch
mm-memcontrol-replace-mem_cgroup_lruvec_online-with-mem_cgroup_online.patch
swaph-move-memcg-related-stuff-to-the-end-of-the-file.patch
mm-vmscan-do-not-scan-anon-pages-if-memcg-swap-limit-is-hit.patch
mm-free-swap-cache-aggressively-if-memcg-swap-is-full.patch
documentation-cgroup-add-memoryswapcurrentmax-description.patch
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