linux-kernel - Re: [PATCH 2/2] page-allocator: Maintain rolling count of pages to free from the PCP

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Date:	Fri, 28 Aug 2009 13:57:19 +0100
From:	Mel Gorman <mel@....ul.ie>
To:	Pekka Enberg <penberg@...helsinki.fi>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Memory Management List <linux-mm@...ck.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] page-allocator: Maintain rolling count of pages to
	free from the PCP

On Fri, Aug 28, 2009 at 03:16:34PM +0300, Pekka Enberg wrote:
> Hi Mel,
> 
> On Fri, Aug 28, 2009 at 11:44 AM, Mel Gorman<mel@....ul.ie> wrote:
> > -               page = list_entry(list->prev, struct page, lru);
> > -               /* have to delete it as __free_one_page list manipulates */
> > -               list_del(&page->lru);
> > -               trace_mm_page_pcpu_drain(page, 0, migratetype);
> > -               __free_one_page(page, zone, 0, migratetype);
> > +               do {
> > +                       page = list_entry(list->prev, struct page, lru);
> > +                       /* must delete as __free_one_page list manipulates */
> > +                       list_del(&page->lru);
> > +                       __free_one_page(page, zone, 0, migratetype);
> > +                       trace_mm_page_pcpu_drain(page, 0, migratetype);
> 
> This calls trace_mm_page_pcpu_drain() *after* __free_one_page(). It's
> probably not a good idea as __free_one_page() can alter the struct
> page in various ways.
> 

While true, does it alter the struct page in any way that matters?

> 
> > +               } while (--count && --batch_free && !list_empty(list));
> >        }
> >        spin_unlock(&zone->lock);
> >  }
> 

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab
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