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SubjectRe: [PATCH 09/10] vmscan: Setup pagevec as late as possible in shrink_page_list()
On Fri, Apr 16, 2010 at 04:54:03PM +0900, KOSAKI Motohiro wrote:
> > shrink_page_list() sets up a pagevec to release pages as according as they
> > are free. It uses significant amounts of stack on the pagevec. This
> > patch adds pages to be freed via pagevec to a linked list which is then
> > freed en-masse at the end. This avoids using stack in the main path that
> > potentially calls writepage().
> >
> > Signed-off-by: Mel Gorman <mel@csn.ul.ie>
> > ---
> > mm/vmscan.c | 34 ++++++++++++++++++++++++++--------
> > 1 files changed, 26 insertions(+), 8 deletions(-)
> >
> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index 9bc1ede..2c22c83 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -619,6 +619,22 @@ static enum page_references page_check_references(struct page *page,
> > return PAGEREF_RECLAIM;
> > }
> >
> > +static void free_page_list(struct list_head *free_list)
> > +{
> > + struct pagevec freed_pvec;
> > + struct page *page, *tmp;
> > +
> > + pagevec_init(&freed_pvec, 1);
> > +
> > + list_for_each_entry_safe(page, tmp, free_list, lru) {
> > + list_del(&page->lru);
> > + if (!pagevec_add(&freed_pvec, page)) {
> > + __pagevec_free(&freed_pvec);
> > + pagevec_reinit(&freed_pvec);
> > + }
> > + }
>
> Need this two line at this? because we need consider number of
> list element are not 14xN.
>
> if (pagevec_count(&freed_pvec))
> __pagevec_free(&freed_pvec);
>

Whoops, yes indeed. Otherwise this potentially leaks and as
SWAP_CLUSTER_MAX is 32, it's often not going to be 14xN

>
> > +}
> > +
> > /*
> > * shrink_page_list() returns the number of reclaimed pages
> > */
> > @@ -627,13 +643,12 @@ static unsigned long shrink_page_list(struct list_head *page_list,
> > enum pageout_io sync_writeback)
> > {
> > LIST_HEAD(ret_pages);
> > - struct pagevec freed_pvec;
> > + LIST_HEAD(free_list);
> > int pgactivate = 0;
> > unsigned long nr_reclaimed = 0;
> >
> > cond_resched();
> >
> > - pagevec_init(&freed_pvec, 1);
> > while (!list_empty(page_list)) {
> > enum page_references references;
> > struct address_space *mapping;
> > @@ -808,10 +823,12 @@ static unsigned long shrink_page_list(struct list_head *page_list,
> > __clear_page_locked(page);
> > free_it:
> > nr_reclaimed++;
> > - if (!pagevec_add(&freed_pvec, page)) {
> > - __pagevec_free(&freed_pvec);
> > - pagevec_reinit(&freed_pvec);
> > - }
> > +
> > + /*
> > + * Is there need to periodically free_page_list? It would
> > + * appear not as the counts should be low
> > + */
> > + list_add(&page->lru, &free_list);
> > continue;
> >
> > cull_mlocked:
> > @@ -834,9 +851,10 @@ keep:
> > list_add(&page->lru, &ret_pages);
> > VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
> > }
> > +
> > + free_page_list(&free_list);
> > +
> > list_splice(&ret_pages, page_list);
> > - if (pagevec_count(&freed_pvec))
> > - __pagevec_free(&freed_pvec);
> > count_vm_events(PGACTIVATE, pgactivate);
> > return nr_reclaimed;
> > }
> > --
> > 1.6.5
> >
>
>
>

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


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