Messages in this thread | | | Date | Thu, 12 Feb 2009 12:25:58 +0100 | From | Johannes Weiner <> | Subject | Re: [PATCH v2] shrink_all_memory() use sc.nr_reclaimed |
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On Thu, Feb 12, 2009 at 04:33:10PM +0900, MinChan Kim wrote: > > Impact: cleanup > > Commit a79311c14eae4bb946a97af25f3e1b17d625985d "vmscan: bail out of > direct reclaim after swap_cluster_max pages" moved the nr_reclaimed > counter into the scan control to accumulate the number of all > reclaimed pages in a reclaim invocation. > > The shrink_all_memory() can use the same mechanism. it increases code > consistency and readability. > > It's based on mmtom 2009-02-11-17-15. > > Signed-off-by: MinChan Kim <minchan.kim@gmail.com> > Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> > Cc: Johannes Weiner <hannes@cmpxchg.org> > Cc: "Rafael J. Wysocki" <rjw@sisk.pl> > Cc: Rik van Riel <riel@redhat.com> > > > --- > mm/vmscan.c | 51 ++++++++++++++++++++++++++++++--------------------- > 1 files changed, 30 insertions(+), 21 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index ae4202b..caa2de5 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -2055,16 +2055,15 @@ unsigned long global_lru_pages(void) > #ifdef CONFIG_PM > /* > * Helper function for shrink_all_memory(). Tries to reclaim 'nr_pages' pages > - * from LRU lists system-wide, for given pass and priority, and returns the > - * number of reclaimed pages > + * from LRU lists system-wide, for given pass and priority. > * > * For pass > 3 we also try to shrink the LRU lists that contain a few pages > */ > -static unsigned long shrink_all_zones(unsigned long nr_pages, int prio, > +static void shrink_all_zones(unsigned long nr_pages, int prio, > int pass, struct scan_control *sc) > { > struct zone *zone; > - unsigned long ret = 0; > + unsigned long nr_reclaimed = 0;
Why this extra variable? You could use sc->nr_reclaimed throughout, like you do in shrink_all_memory().
> for_each_populated_zone(zone) { > enum lru_list l; > @@ -2087,14 +2086,16 @@ static unsigned long shrink_all_zones(unsigned long nr_pages, int prio, > > zone->lru[l].nr_scan = 0; > nr_to_scan = min(nr_pages, lru_pages); > - ret += shrink_list(l, nr_to_scan, zone, > + nr_reclaimed += shrink_list(l, nr_to_scan, zone, > sc, prio); > - if (ret >= nr_pages) > - return ret; > + if (nr_reclaimed >= nr_pages) { > + sc->nr_reclaimed = nr_reclaimed; > + return; > + } > } > } > } > - return ret; > + sc->nr_reclaimed = nr_reclaimed; > } > > /* > @@ -2126,13 +2127,15 @@ unsigned long shrink_all_memory(unsigned long nr_pages) > /* If slab caches are huge, it's better to hit them first */ > while (nr_slab >= lru_pages) { > reclaim_state.reclaimed_slab = 0; > - shrink_slab(nr_pages, sc.gfp_mask, lru_pages); > + shrink_slab(sc.swap_cluster_max, sc.gfp_mask, lru_pages); > if (!reclaim_state.reclaimed_slab) > break; > > - ret += reclaim_state.reclaimed_slab; > - if (ret >= nr_pages) > + sc.nr_reclaimed += reclaim_state.reclaimed_slab; > + if (sc.nr_reclaimed >= sc.swap_cluster_max) { > + ret = sc.nr_reclaimed;
Why do you still maintain `ret'? Just return sc.nr_reclaimed at the end and get rid of ret alltogether.
Using sc.swap_cluster_max here seems to be a good idea at first sight but really it is not.
Usually, swap_cluster_max is smaller than the reclaim goal and reclaim code uses it combined with other conditions to bail out BEFORE the original reclaim goal is met. But sc.swap_cluster_max IS our original reclaim goal, so it means something different.
It's btw buggy, we never decrease swap_cluster_max which leads to funky overreclaim in shrink_inactive_list(). I will send the original patch from Kosaki-san for using sc->nr_reclaimed and a patch for the overreclaim problem.
Hannes
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