Re: [RFC][PATCH 1/5] memcg: change for softlimit.

Balbir Singh
2009-08-28T07:20:13Z

* KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-08-28 13:23:21]:

> This patch tries to modify softlimit handling in memcg/res_counter.
> There are 2 reasons in general.
>
> 1. soft_limit can use only against sub-hierarchy root.
> Because softlimit tree is sorted by usage, putting prural groups
> under hierarchy (which shares usage) will just adds noise and unnecessary
> mess. This patch limits softlimit feature only to hierarchy root.
> This will make softlimit-tree maintainance better.
>
> 2. In these days, it's reported that res_counter can be bottleneck in
> massively parallel enviroment. We need to reduce jobs under spinlock.
> The reason we check softlimit at res_counter_charge() is that any member
> in hierarchy can have softlimit.
> But by chages in "1", only hierarchy root has soft_limit. We can omit
> hierarchical check in res_counter.
>
> After this patch, soft limit is avaliable only for root of sub-hierarchy.
> (Anyway, softlimit for hierarchy children just makes users confused, hard-to-use)
>

I need some time to digest this change, if the root is a hiearchy root
then only root can support soft limits? I think the change makes it
harder to use soft limits. Please help me understand better.

--
Balbir