Commit e2717995 authored by Michal Koutný's avatar Michal Koutný Committed by Tejun Heo
Browse files

docs: cgroup: Explain reclaim protection target 



The protection target is necessary to understand how effective reclaim
protection applies in the hierarchy.

Signed-off-by: default avatarMichal Koutný <mkoutny@suse.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 1dc830ee

Documentation/admin-guide/cgroup-v2.rst

+21 −3
Original line number Diff line number Diff line
@@ -53,7 +53,8 @@ v1 is available under :ref:`Documentation/admin-guide/cgroup-v1/index.rst <cgrou 
     5-2. Memory

       5-2-1. Memory Interface Files

       5-2-2. Usage Guidelines

       5-2-3. Memory Ownership

       5-2-3. Reclaim Protection

       5-2-4. Memory Ownership

     5-3. IO

       5-3-1. IO Interface Files

       5-3-2. Writeback
@@ -1317,7 +1318,7 @@ PAGE_SIZE multiple when read back. 
	smaller overages.



	Effective min boundary is limited by memory.min values of

	all ancestor cgroups. If there is memory.min overcommitment

	ancestor cgroups. If there is memory.min overcommitment

	(child cgroup or cgroups are requiring more protected memory

	than parent will allow), then each child cgroup will get

	the part of parent's protection proportional to its
@@ -1343,7 +1344,7 @@ PAGE_SIZE multiple when read back. 
	smaller overages.



	Effective low boundary is limited by memory.low values of

	all ancestor cgroups. If there is memory.low overcommitment

	ancestor cgroups. If there is memory.low overcommitment

	(child cgroup or cgroups are requiring more protected memory

	than parent will allow), then each child cgroup will get

	the part of parent's protection proportional to its
@@ -1934,6 +1935,23 @@ memory - is necessary to determine whether a workload needs more 
memory; unfortunately, memory pressure monitoring mechanism isn't

implemented yet.



Reclaim Protection

~~~~~~~~~~~~~~~~~~



The protection configured with "memory.low" or "memory.min" applies relatively

to the target of the reclaim (i.e. any of memory cgroup limits, proactive

memory.reclaim or global reclaim apparently located in the root cgroup).

The protection value configured for B applies unchanged to the reclaim

targeting A (i.e. caused by competition with the sibling E)::



		root - ... - A - B - C

		              \    ` D

		               ` E



When the reclaim targets ancestors of A, the effective protection of B is

capped by the protection value configured for A (and any other intermediate

ancestors between A and the target).





Memory Ownership

~~~~~~~~~~~~~~~~