Re: [PATCH 17/25] Do not call get_pageblock_migratetype() more than necessary

Mel Gorman
2009-04-21T16:12:10Z

On Tue, Apr 21, 2009 at 08:03:10PM +0900, KOSAKI Motohiro wrote:
> > get_pageblock_migratetype() is potentially called twice for every page
> > free. Once, when being freed to the pcp lists and once when being freed
> > back to buddy. When freeing from the pcp lists, it is known what the
> > pageblock type was at the time of free so use it rather than rechecking.
> > In low memory situations under memory pressure, this might skew
> > anti-fragmentation slightly but the interference is minimal and
> > decisions that are fragmenting memory are being made anyway.
> >
> > Signed-off-by: Mel Gorman <mel@csn.ul.ie>
> > Reviewed-by: Christoph Lameter <cl@linux-foundation.org>
> > ---
> > mm/page_alloc.c | 16 ++++++++++------
> > 1 files changed, 10 insertions(+), 6 deletions(-)
> >
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index c57c602..a1ca038 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -456,16 +456,18 @@ static inline int page_is_buddy(struct page *page, struct page *buddy,
> > */
> >
> > static inline void __free_one_page(struct page *page,
> > - struct zone *zone, unsigned int order)
> > + struct zone *zone, unsigned int order,
> > + int migratetype)
> > {
> > unsigned long page_idx;
> > int order_size = 1 << order;
> > - int migratetype = get_pageblock_migratetype(page);
> >
> > if (unlikely(PageCompound(page)))
> > if (unlikely(destroy_compound_page(page, order)))
> > return;
> >
> > + VM_BUG_ON(migratetype == -1);
> > +
> > page_idx = page_to_pfn(page) & ((1 << MAX_ORDER) - 1);
> >
> > VM_BUG_ON(page_idx & (order_size - 1));
> > @@ -534,17 +536,18 @@ static void free_pages_bulk(struct zone *zone, int count,
> > page = list_entry(list->prev, struct page, lru);
> > /* have to delete it as __free_one_page list manipulates */
> > list_del(&page->lru);
> > - __free_one_page(page, zone, order);
> > + __free_one_page(page, zone, order, page_private(page));
> > }
> > spin_unlock(&zone->lock);
>
> looks good.
> Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
>
>
> btw, I can't review rest patch today. I plan to do that tommorow, sorry.
>

No problem. Thanks a million for the work you've done so far. It was a
big help and you caught a fair few problems in there.

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