Re: [RFC][PATCH 1/2] memcg: res_counter hierarchy

KAMEZAWA Hiroyuki wrote:
This patch tries to implements _simple_ 'hierarchy policy' in res_counter.

While several policy of hierarchy can be considered, this patch implements
simple one
- the parent includes, over-commits the child
- there are no shared resource

I am not sure if this is desirable. The concept of a hierarchy applies really
well when there are shared resources.

- dynamic hierarchy resource usage management in the kernel is not necessary


Could you please elaborate as to why? I am not sure I understand your point

works as following.

1. create a child. set default child limits to be 0.
2. set limit to child.
2-a. before setting limit to child, prepare enough room in parent.
2-b. increase 'usage' of parent by child's limit.

The problem with this is that you are forcing the parent will run into a reclaim
loop even if the child is not using the assigned limit to it.

3. the child sets its limit to the val moved from the parent.
the parent remembers what amount of resource is to the children.


All of this needs to be dynamic

Above means that
- a directory's usage implies the sum of all sub directories +
own usage.
- there are no shared resource between parent <-> child.

Pros.
- simple and easy policy.
- no hierarchy overhead.
- no resource share among child <-> parent. very suitable for multilevel
resource isolation.

Sharing is an important aspect of hierachies. I am not convinced of this
approach. Did you look at the patches I sent out? Was there something
fundamentally broken in them?

[snip]

--
Warm Regards,
Balbir Singh
Linux Technology Center
IBM, ISTL
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

Relevant Pages

  • Re: SQL, related records (quotes)
    ... Let's say for the hierarchy itself we decide on ... child parent ... child B to reference for referential integrity and what meaning the ... possible with a vertex involving itself as a root node of a hierarchy. ...
    (comp.databases.theory)
  • Re: [RFC][PATCH 1/2] memcg: res_counter hierarchy
    ... While several policy of hierarchy can be considered, ... create a child. ... prepare enough room in parent. ... One way to manage hierarchies other than via limits is to use shares (please see ...
    (Linux-Kernel)
  • Re: Re: [RFC][PATCH 1/2] memcg: res_counter hierarchy
    ... While several policy of hierarchy can be considered, ... there are no shared resource ... create a child. ... prepare enough room in parent. ...
    (Linux-Kernel)
  • [RFC][PATCH 1/2] memcg: res_counter hierarchy
    ... This patch tries to implements _simple_ 'hierarchy policy' in res_counter. ... dynamic hierarchy resource usage management in the kernel is not necessary ... create a child. ... prepare enough room in parent. ...
    (Linux-Kernel)
  • object hierarchy, parent-child links, etc
    ... I am trying to construct an object hierarchy for some relatively simple ... objects I am trying to expose to COM / Automation for use in scripting. ... in which the parent has one statically-created child member. ...
    (microsoft.public.vc.atl)