On Wed, Apr 27, 2011 at 01:25:20AM +0900, Minchan Kim wrote:
> In some __zone_reclaim case, we don't want to shrink mapped page.
> Nonetheless, we have isolated mapped page and re-add it into
> LRU's head. It's unnecessary CPU overhead and makes LRU churning.
>
> Of course, when we isolate the page, the page might be mapped but
> when we try to migrate the page, the page would be not mapped.
> So it could be migrated. But race is rare and although it happens,
> it's no big deal.
>
> Cc: Christoph Lameter <cl@xxxxxxxxx>
> Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
> Cc: Mel Gorman <mgorman@xxxxxxx>
> Cc: Rik van Riel <riel@xxxxxxxxxx>
> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
> Signed-off-by: Minchan Kim <minchan.kim@xxxxxxxxx>
> index 71d2da9..e8d6190 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1147,7 +1147,8 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
>
> static unsigned long isolate_pages_global(unsigned long nr,
> struct list_head *dst,
> - unsigned long *scanned, int order,
> + unsigned long *scanned,
> + struct scan_control *sc,
> int mode, struct zone *z,
> int active, int file)
> {
> @@ -1156,8 +1157,8 @@ static unsigned long isolate_pages_global(unsigned long nr,
> lru += LRU_ACTIVE;
> if (file)
> lru += LRU_FILE;
> - return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
> - mode, file, 0, 0);
> + return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, sc->order,
> + mode, file, 0, !sc->may_unmap);
> }
>
Why not take may_writepage into account for dirty pages?
> /*
> @@ -1407,7 +1408,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
>
> if (scanning_global_lru(sc)) {
> nr_taken = isolate_pages_global(nr_to_scan,
> - &page_list, &nr_scanned, sc->order,
> + &page_list, &nr_scanned, sc,
> sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ?
> ISOLATE_BOTH : ISOLATE_INACTIVE,
> zone, 0, file);
> @@ -1531,7 +1532,7 @@ static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
> spin_lock_irq(&zone->lru_lock);
> if (scanning_global_lru(sc)) {
> nr_taken = isolate_pages_global(nr_pages, &l_hold,
> - &pgscanned, sc->order,
> + &pgscanned, sc,
> ISOLATE_ACTIVE, zone,
> 1, file);
> zone->pages_scanned += pgscanned;
> --
> 1.7.1
>
--
Mel Gorman
SUSE Labs
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