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SubjectRe: [patch 08/11 -mmotm] oom: invoke oom killer for __GFP_NOFAIL
On Mon, 11 May 2009 10:45:05 +0900 (JST)
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> wrote:

> > On Mon, 11 May 2009, KOSAKI Motohiro wrote:
> >
> > > > The oom killer must be invoked regardless of the order if the allocation
> > > > is __GFP_NOFAIL, otherwise it will loop forever when reclaim fails to
> > > > free some memory.
> > >
> > > This is intensional behavior. plus you change very widely caller bahavior.
> > > if you don't have good test program, I nak this.
> > >
> >
> > What exactly are you objecting to? You don't want the oom killer called
> > for a __GFP_NOFAIL allocation above PAGE_ALLOC_COSTLY_ORDER that could not
> > reclaim any memory and would prefer that it loop endlessly in the page
> > allocator? What's the purpose of that if the oom killer could free a very
> > large memory hogging task?
>
> My point is, if we change gfp-flags meaning, we should change
> unintentional affected caller.
>
> Do you oppose this?
>

I agree KOSAKI's opinion.
We already have a different flags.

* __GFP_REPEAT: Try hard to allocate the memory, but the allocation attempt
* _might_ fail. This depends upon the particular VM implementation.
*
* __GFP_NOFAIL: The VM implementation _must_ retry infinitely: the caller
* cannot handle allocation failures.

When we use __GFP_NOFAIL, we always have to use it carefully.
If you change the meaning of __GFP_NOFAIL, the intension of them who have been used it carefully may be lost. It's my concern.


--
Kinds Regards
Minchan Kim


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