Re: [PATCH 1/3] mm/page_alloc: don't break highest order freepage if steal

[Vlastimil Babka]

On 05/12/2015 09:51 AM, Vlastimil Babka wrote:
> >    {
> >    	struct page *page;
> > +	bool steal_fallback;
> >
> > -retry_reserve:
> > +retry:
> >    	page = __rmqueue_smallest(zone, order, migratetype);
> >
> >    	if (unlikely(!page) && migratetype != MIGRATE_RESERVE) {
> >    		if (migratetype == MIGRATE_MOVABLE)
> >    			page = __rmqueue_cma_fallback(zone, order);
> >
> > -		if (!page)
> > -			page = __rmqueue_fallback(zone, order, migratetype);
> > +		if (page)
> > +			goto out;
> > +
> > +		steal_fallback = __rmqueue_fallback(zone, order, migratetype);

Oh and the variable can be probably replaced by calling 
__rmqueue_fallback directly in the if() below.

> >    		/*
> >    		 * Use MIGRATE_RESERVE rather than fail an allocation. goto
> >    		 * is used because __rmqueue_smallest is an inline function
> >    		 * and we want just one call site
> >    		 */
> > -		if (!page) {
> > +		if (!steal_fallback)
> >    			migratetype = MIGRATE_RESERVE;
> > -			goto retry_reserve;
> > -		}
> > +
> > +		goto retry;
> >    	}
> >
> > +out:
> >    	trace_mm_page_alloc_zone_locked(page, order, migratetype);
> >    	return page;
> >    }
>
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