Re: [RFC][PATCH 7/6] memcg: add atribute (for change bahavior ofrmdir)

[KAMEZAWA Hiroyuki]

Hugh Dickins said:
> On Thu, 6 Nov 2008, KAMEZAWA Hiroyuki wrote:
>> On Thu, 06 Nov 2008 12:24:11 +0530
>> Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx> wrote:
>> > KAMEZAWA Hiroyuki wrote:
>> > >
>> > > 1. change force_empty to do move account rather than forget all
>> >
>> > I would like this to be selectable, please. We don't want to break
>> behaviour and
>> > not everyone would like to pay the cost of movement.
>>
>> How about a patch like this ? I'd like to move this as [2/7], if
>> possible.
>> It obviously needs painful rework. If I found it difficult, schedule
>> this as [7/7].
>>
>> BTW, cost of movement itself is not far from cost for force_empty.
>>
>> If you can't find why "forget" is bad, please consider one more day.
>
> My recollection from a year ago is that force_empty totally violated
> the rules established elsewhere, making a nonsense of it all: once a
> force_empty had been done, you couldn't really be sure of anything
> (perhaps it deserved a Taint flag).
>
yes. that was terrible. (but necessary to do so because we accounted
pages not on LRU or some other reason.)

> Without studying your proposals at all, I do believe you've a good
> chance of creating a sensible and consistent force_empty by moving
> account, and abandoning the old "forget all" approach completely.
>

yes. I'm very encouraged. thanks!
After patch [1/6]
  -> move all at force empty
After this
  -> move all or free (not forget) all.

-Kame


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