On Mon, Mar 18, 2013 at 07:35:04PM +0800, Hillf Danton wrote:
> On Sun, Mar 17, 2013 at 9:04 PM, Mel Gorman <mgorman@xxxxxxx> wrote:
> > In the past, kswapd makes a decision on whether to compact memory after the
> > pgdat was considered balanced. This more or less worked but it is late to
> > make such a decision and does not fit well now that kswapd makes a decision
> > whether to exit the zone scanning loop depending on reclaim progress.
> >
> > This patch will compact a pgdat if at least the requested number of pages
> > were reclaimed from unbalanced zones for a given priority. If any zone is
> > currently balanced, kswapd will not call compaction as it is expected the
> > necessary pages are already available.
> >
> > Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
> > ---
> > mm/vmscan.c | 52 +++++++++++++++++++++-------------------------------
> > 1 file changed, 21 insertions(+), 31 deletions(-)
> >
> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index 279d0c2..7513bd1 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -2694,8 +2694,11 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
> >
> > do {
> > unsigned long lru_pages = 0;
> > + unsigned long nr_to_reclaim = 0;
> > unsigned long nr_reclaimed = sc.nr_reclaimed;
> > + unsigned long this_reclaimed;
> > bool raise_priority = true;
> > + bool pgdat_needs_compaction = true;
>
> To show that compaction is needed iff non order-o reclaim,
> bool do_compaction = !!order;
>
An order check is already made where relevant. It could be part of how
pgdat_needs_compaction gets initialised but I did not think it helped
readability.
> >
> > /*
> > * Scan in the highmem->dma direction for the highest
> > @@ -2743,7 +2746,17 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
> > for (i = 0; i <= end_zone; i++) {
> > struct zone *zone = pgdat->node_zones + i;
> >
> > + if (!populated_zone(zone))
> > + continue;
> > +
> > lru_pages += zone_reclaimable_pages(zone);
> > +
> > + /* Check if the memory needs to be defragmented */
> Enrich the comment with, say,
> /*If any zone is
> currently balanced, kswapd will not call compaction as it is expected the
> necessary pages are already available.*/
> please since a big one is deleted below.
>
Ok, done.
--
Mel Gorman
SUSE Labs
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