Re: [patch 08/11 -mmotm] oom: invoke oom killer for __GFP_NOFAIL

[Minchan Kim]

On Mon, 11 May 2009 10:45:05 +0900 (JST)
KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> 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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/