Messages in this thread | | | Date | Tue, 09 Apr 2013 16:41:36 +0800 | From | Simon Jeons <> | Subject | Re: [PATCH 08/10] mm: vmscan: Have kswapd shrink slab only once per priority |
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Hi Joonsoo, On 04/09/2013 02:53 PM, Joonsoo Kim wrote: > Hello, Mel. > Sorry for too late question. > > On Sun, Mar 17, 2013 at 01:04:14PM +0000, Mel Gorman wrote: >> If kswaps fails to make progress but continues to shrink slab then it'll >> either discard all of slab or consume CPU uselessly scanning shrinkers. >> This patch causes kswapd to only call the shrinkers once per priority. >> >> Signed-off-by: Mel Gorman <mgorman@suse.de> >> --- >> mm/vmscan.c | 28 +++++++++++++++++++++------- >> 1 file changed, 21 insertions(+), 7 deletions(-) >> >> diff --git a/mm/vmscan.c b/mm/vmscan.c >> index 7d5a932..84375b2 100644 >> --- a/mm/vmscan.c >> +++ b/mm/vmscan.c >> @@ -2661,9 +2661,10 @@ static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order, long remaining, >> */ >> static bool kswapd_shrink_zone(struct zone *zone, >> struct scan_control *sc, >> - unsigned long lru_pages) >> + unsigned long lru_pages, >> + bool shrinking_slab) >> { >> - unsigned long nr_slab; >> + unsigned long nr_slab = 0; >> struct reclaim_state *reclaim_state = current->reclaim_state; >> struct shrink_control shrink = { >> .gfp_mask = sc->gfp_mask, >> @@ -2673,9 +2674,15 @@ static bool kswapd_shrink_zone(struct zone *zone, >> sc->nr_to_reclaim = max(SWAP_CLUSTER_MAX, high_wmark_pages(zone)); >> shrink_zone(zone, sc); >> >> - reclaim_state->reclaimed_slab = 0; >> - nr_slab = shrink_slab(&shrink, sc->nr_scanned, lru_pages); >> - sc->nr_reclaimed += reclaim_state->reclaimed_slab; >> + /* >> + * Slabs are shrunk for each zone once per priority or if the zone >> + * being balanced is otherwise unreclaimable >> + */ >> + if (shrinking_slab || !zone_reclaimable(zone)) { >> + reclaim_state->reclaimed_slab = 0; >> + nr_slab = shrink_slab(&shrink, sc->nr_scanned, lru_pages); >> + sc->nr_reclaimed += reclaim_state->reclaimed_slab; >> + } >> >> if (nr_slab == 0 && !zone_reclaimable(zone)) >> zone->all_unreclaimable = 1; > Why shrink_slab() is called here? > I think that outside of zone loop is better place to run shrink_slab(), > because shrink_slab() is not directly related to a specific zone.
True.
> > And this is a question not related to this patch. > Why nr_slab is used here to decide zone->all_unreclaimable? > nr_slab is not directly related whether a specific zone is reclaimable > or not, and, moreover, nr_slab is not directly related to number of > reclaimed pages. It just say some objects in the system are freed. > > This question comes from my ignorance, so please enlighten me.
Good question, I also want to know. ;-)
> > Thanks. > >> @@ -2713,6 +2720,7 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order, >> int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */ >> unsigned long nr_soft_reclaimed; >> unsigned long nr_soft_scanned; >> + bool shrinking_slab = true; >> struct scan_control sc = { >> .gfp_mask = GFP_KERNEL, >> .priority = DEF_PRIORITY, >> @@ -2861,7 +2869,8 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order, >> * already being scanned that that high >> * watermark would be met at 100% efficiency. >> */ >> - if (kswapd_shrink_zone(zone, &sc, lru_pages)) >> + if (kswapd_shrink_zone(zone, &sc, >> + lru_pages, shrinking_slab)) >> raise_priority = false; >> >> nr_to_reclaim += sc.nr_to_reclaim; >> @@ -2900,6 +2909,9 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order, >> pfmemalloc_watermark_ok(pgdat)) >> wake_up(&pgdat->pfmemalloc_wait); >> >> + /* Only shrink slab once per priority */ >> + shrinking_slab = false; >> + >> /* >> * Fragmentation may mean that the system cannot be rebalanced >> * for high-order allocations in all zones. If twice the >> @@ -2925,8 +2937,10 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order, >> * Raise priority if scanning rate is too low or there was no >> * progress in reclaiming pages >> */ >> - if (raise_priority || !this_reclaimed) >> + if (raise_priority || !this_reclaimed) { >> sc.priority--; >> + shrinking_slab = true; >> + } >> } while (sc.priority >= 1 && >> !pgdat_balanced(pgdat, order, *classzone_idx)); >> >> -- >> 1.8.1.4 >> >> -- >> To unsubscribe, send a message with 'unsubscribe linux-mm' in >> the body to majordomo@kvack.org. For more info on Linux MM, >> see: http://www.linux-mm.org/ . >> Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a> > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@kvack.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
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