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authorJohannes Weiner <hannes@cmpxchg.org>2014-12-10 15:44:52 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2014-12-10 17:41:09 -0800
commit1306a85aed3ec3db98945aafb7dfbe5648a1203c (patch)
tree63643e556c64118d963020758faf915325ba613c /Documentation
parentmm: memcontrol: remove stale page_cgroup_lock comment (diff)
downloadlinux-dev-1306a85aed3ec3db98945aafb7dfbe5648a1203c.tar.xz
linux-dev-1306a85aed3ec3db98945aafb7dfbe5648a1203c.zip
mm: embed the memcg pointer directly into struct page
Memory cgroups used to have 5 per-page pointers. To allow users to disable that amount of overhead during runtime, those pointers were allocated in a separate array, with a translation layer between them and struct page. There is now only one page pointer remaining: the memcg pointer, that indicates which cgroup the page is associated with when charged. The complexity of runtime allocation and the runtime translation overhead is no longer justified to save that *potential* 0.19% of memory. With CONFIG_SLUB, page->mem_cgroup actually sits in the doubleword padding after the page->private member and doesn't even increase struct page, and then this patch actually saves space. Remaining users that care can still compile their kernels without CONFIG_MEMCG. text data bss dec hex filename 8828345 1725264 983040 11536649 b00909 vmlinux.old 8827425 1725264 966656 11519345 afc571 vmlinux.new [mhocko@suse.cz: update Documentation/cgroups/memory.txt] Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Michal Hocko <mhocko@suse.cz> Acked-by: Vladimir Davydov <vdavydov@parallels.com> Acked-by: David S. Miller <davem@davemloft.net> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: "Kirill A. Shutemov" <kirill@shutemov.name> Cc: Michal Hocko <mhocko@suse.cz> Cc: Vladimir Davydov <vdavydov@parallels.com> Cc: Tejun Heo <tj@kernel.org> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Acked-by: Konstantin Khlebnikov <koct9i@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/cgroups/memory.txt5
1 files changed, 5 insertions, 0 deletions
diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt
index 67613ff0270c..46b2b5080317 100644
--- a/Documentation/cgroups/memory.txt
+++ b/Documentation/cgroups/memory.txt
@@ -1,5 +1,10 @@
Memory Resource Controller
+NOTE: This document is hopelessly outdated and it asks for a complete
+ rewrite. It still contains a useful information so we are keeping it
+ here but make sure to check the current code if you need a deeper
+ understanding.
+
NOTE: The Memory Resource Controller has generically been referred to as the
memory controller in this document. Do not confuse memory controller
used here with the memory controller that is used in hardware.