Re: [PATCH 2/3] mm: page allocator: Calculate a better estimate of NR_FREE_PAGES when memory is low and kswapd is awake

[KOSAKI Motohiro]

> On Wed, 1 Sep 2010, Mel Gorman wrote:
> 
> > > > >         if (delta < 0 && abs(delta) > nr_free_pages)
> > > > >                 delta = -nr_free_pages;
> > >
> > > Not sure what the point here is. If the delta is going below zero then
> > > there was a concurrent operation updating the counters negatively while
> > > we summed up the counters.
> >
> > The point is if the negative delta is greater than the current value of
> > nr_free_pages then nr_free_pages would underflow when delta is applied to it.
> 
> Ok. then
> 
> 	nr_free_pages += delta;
> 	if (nr_free_pages < 0)
> 		nr_free_pages = 0;

nr_free_pages is unsined. this wouldn't works ;)




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