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

KAMEZAWA Hiroyuki
2009-08-28T14:58:41Z

Balbir Singh wrote:
> * KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-08-28
> 23:29:09]:
>
>> Balbir Singh wrote:
>> > * KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-08-28
>> > 16:35:23]:
>> >
>>
>> >>
>> >> Current soft-limit RB-tree will be easily broken i.e. not-sorted
>> >> correctly
>> >> if used under use_hierarchy=1.
>> >>
>> >
>> > Not true, I think the sorted-ness is delayed and is seen when we pick
>> > a tree for reclaim. Think of it as being lazy :)
>> >
>> plz explain how enexpectedly unsorted RB-tree can work sanely.
>>
>>
>
> There are two checks built-in
>
> 1. In the reclaim path (we see how much to reclaim, compared to the
> soft limit)
> 2. In the dequeue path where we check if we really are over soft limit
>
that's not a point.

> I did lot of testing with the time based approach and found no broken
> cases, I;ve been testing it with the mmotm (event based approach and I
> am yet to see a broken case so far).
>
I'm sorry if I don't understand RB-tree.
I think RB-tree is a system which can sort inputs passed by caller
one by one and will be in broken state if value of nodes changed
while it's in tree. Wrong ?
While a subtree is
7
/ \
3 9
And, by some magic, the value can be changed without extract
7
/ \
13 9
The biggest is 13. But the biggest number which will be selecte will be "9".

Thanks,
-Kame