[Devel] Re: [ckrm-tech] [RFC] [PATCH 00/12] CKRM after a major overhaul

[KUROSAWA Takahiro]

On Mon, 24 Apr 2006 10:45:59 +0400
Kirill Korotaev <dev at openvz.org> wrote:

> >>>>Yes, it is effective, and the reclamation is O(1) too. It has couple of
> >>>>problems by design, (1) doesn't handle shared pages and (2) doesn't
> >>>>provide support for both min_shares and max_shares.
> >>>
> >>>Right.  I wanted to show proof-of-cencept of the pzone based controller
> >>>and implemented minimal features necessary as the memory controller.
> >>>So, the pzone based controller still needs development and some cleanup.
> >>
> >>Just out of curiosity, how it was meassured that it is effective?
> > 
> > I don't have any benchmark numbers yet, so I can't explain the
> > effectiveness with numbers.  I've been looking for the way to
> > measure the cost of pzones correctly, but I've not found it out yet.
> > 
> >>How does it work when there is a global memory shortage in the system?
> > 
> > I guess you are referring to the situation that global memory is running
> > out but there are free pages in pzones.  These free pages in pzones are
> > handled as reserved for pzone users and not used even in global memory 
> > shortage.
> ok. Let me explain what I mean.
> Imagine the situation with global memory shortage. In kernel, there are 
> threads which do some job behalf the user, e.g. kjournald, loop etc. If 
> the user has some pzone memory, but these threads fail to do their job 
> some nasty things can happen (ext3 problems, deadlocks, OOM etc.)
> If such behaviour is ok for you, then great. But did you consider it?
> 
> Also, I can't understand how it works with OOM killer. If pzones has 
> enough memory, but there is a global shortage, who will be killed?

I understand.
IMHO, only the system processes should use global memory.
User processes that may cause such memory shortage should be 
enclosed in pzones first.

Thanks,

-- 
KUROSAWA, Takahiro