Commit 2ee06468 authored by Vladimir Davydov's avatar Vladimir Davydov Committed by Linus Torvalds
Browse files

Documentation/memcg: warn about incomplete kmemcg state 



Kmemcg is currently under development and lacks some important features.
In particular, it does not have support of kmem reclaim on memory pressure
inside cgroup, which practically makes it unusable in real life.  Let's
warn about it in both Kconfig and Documentation to prevent complaints
arising.

Signed-off-by: default avatarVladimir Davydov <vdavydov@parallels.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 613813e8

Documentation/cgroups/memory.txt

+5 −0
Original line number Diff line number Diff line
@@ -270,6 +270,11 @@ When oom event notifier is registered, event will be delivered. 


2.7 Kernel Memory Extension (CONFIG_MEMCG_KMEM)



WARNING: Current implementation lacks reclaim support. That means allocation

	 attempts will fail when close to the limit even if there are plenty of

	 kmem available for reclaim. That makes this option unusable in real

	 life so DO NOT SELECT IT unless for development purposes.



With the Kernel memory extension, the Memory Controller is able to limit

the amount of kernel memory used by the system. Kernel memory is fundamentally

different than user memory, since it can't be swapped out, which makes it

init/Kconfig

+6 −0
Original line number Diff line number Diff line
@@ -996,6 +996,12 @@ config MEMCG_KMEM 
	  the kmem extension can use it to guarantee that no group of processes

	  will ever exhaust kernel resources alone.



	  WARNING: Current implementation lacks reclaim support. That means

	  allocation attempts will fail when close to the limit even if there

	  are plenty of kmem available for reclaim. That makes this option

	  unusable in real life so DO NOT SELECT IT unless for development

	  purposes.



config CGROUP_HUGETLB

	bool "HugeTLB Resource Controller for Control Groups"

	depends on RESOURCE_COUNTERS && HUGETLB_PAGE

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