Messages in this thread Patch in this message | | | From | Balbir Singh <> | Date | Sun, 16 Nov 2008 13:40:40 +0530 | Subject | [mm] [PATCH 1/4] Memory cgroup hierarchy documentation (v4) |
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Documentation updates for hierarchy support
Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com> ---
Documentation/controllers/memory.txt | 38 ++++++++++++++++++++++++++++++++++- 1 file changed, 37 insertions(+), 1 deletion(-)
diff -puN Documentation/controllers/memory.txt~memcg-hierarchy-documentation Documentation/controllers/memory.txt --- linux-2.6.28-rc4/Documentation/controllers/memory.txt~memcg-hierarchy-documentation 2008-11-16 13:14:39.000000000 +0530 +++ linux-2.6.28-rc4-balbir/Documentation/controllers/memory.txt 2008-11-16 13:14:39.000000000 +0530 @@ -289,8 +289,44 @@ will be charged as a new owner of it. Because rmdir() moves all pages to parent, some out-of-use page caches can be moved to the parent. If you want to avoid that, force_empty will be useful. +6. Hierarchy support -6. TODO +The memory controller supports a deep hierarchy and hierarchical accounting. +The hierarchy is created by creating the appropriate cgroups in the +cgroup filesystem. Consider for example, the following cgroup filesystem +hierarchy + + root + / | \ + / | \ + a b c + | \ + | \ + d e + +In the diagram above, with hierarchical accounting enabled, all memory +usage of e, is accounted to its ancestors up until the root (i.e, c and root), +that has memory.use_hierarchy enabled. If one of the ancestors goes over its +limit, the reclaim algorithm reclaims from the tasks in the ancestor and the +children of the ancestor. + +6.1 Enabling hierarchical accounting and reclaim + +The memory controller by default disables the hierarchy feature. Support +can be enabled by writing 1 to memory.use_hierarchy file of the root cgroup + +# echo 1 > memory.use_hierarchy + +The feature can be disabled by + +# echo 0 > memory.use_hierarchy + +NOTE1: Enabling/disabling will fail if the cgroup already has other +cgroups created below it. + +NOTE2: This feature can be enabled/disabled per subtree. + +7. TODO 1. Add support for accounting huge pages (as a separate controller) 2. Make per-cgroup scanner reclaim not-shared pages first _ -- Balbir
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