Messages in this thread Patch in this message | | | Date | Mon, 22 Sep 2008 19:58:42 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | [PATCH 3/13] memcg: nolimit root cgroup |
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Make root cgroup of memory resource controller to have no limit.
By this, users cannot set limit to root group. This is for making root cgroup as a kind of trash-can.
For accounting pages which has no owner, which are created by force_empty, we need some cgroup with no_limit. A patch for rewriting force_empty will will follow this one.
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Index: mmotm-2.6.27-rc6+/mm/memcontrol.c =================================================================== --- mmotm-2.6.27-rc6+.orig/mm/memcontrol.c +++ mmotm-2.6.27-rc6+/mm/memcontrol.c @@ -136,6 +136,9 @@ struct mem_cgroup { }; static struct mem_cgroup init_mem_cgroup; +#define is_root_cgroup(cgrp) ((cgrp) == &init_mem_cgroup) + + /* * We use the lower bit of the page->page_cgroup pointer as a bit spin * lock. We need to ensure that page->page_cgroup is at least two @@ -944,6 +947,10 @@ static int mem_cgroup_write(struct cgrou switch (cft->private) { case RES_LIMIT: + if (is_root_cgroup(memcg)) { + ret = -EINVAL; + break; + } /* This function does all necessary parse...reuse it */ ret = res_counter_memparse_write_strategy(buffer, &val); if (!ret) Index: mmotm-2.6.27-rc6+/Documentation/controllers/memory.txt =================================================================== --- mmotm-2.6.27-rc6+.orig/Documentation/controllers/memory.txt +++ mmotm-2.6.27-rc6+/Documentation/controllers/memory.txt @@ -121,6 +121,9 @@ The corresponding routines that remove a a page from Page Cache is used to decrement the accounting counters of the cgroup. +The root cgroup is not allowed to be set limit but usage is accounted. +For controlling usage of memory, you need to create a cgroup. + 2.3 Shared Page Accounting Shared pages are accounted on the basis of the first touch approach. The @@ -172,6 +175,7 @@ We can alter the memory limit: NOTE: We can use a suffix (k, K, m, M, g or G) to indicate values in kilo, mega or gigabytes. +Note: root cgroup is not able to be set limit. # cat /cgroups/0/memory.limit_in_bytes 4194304
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