Messages in this thread | | | Subject | Re: [PATCH 11/27] mm: vmscan: Do not reclaim from kswapd if there is any eligible zone | From | Vlastimil Babka <> | Date | Thu, 16 Jun 2016 12:08:58 +0200 |
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On 06/09/2016 08:04 PM, Mel Gorman wrote: > kswapd scans from highest to lowest for a zone that requires balancing. > This was necessary when reclaim was per-zone to fairly age pages on > lower zones. Now that we are reclaiming on a per-node basis, any eligible > zone can be used and pages will still be aged fairly. This patch avoids > reclaiming excessively unless buffer_heads are over the limit and it's > necessary to reclaim from a higher zone than requested by the waker of > kswapd to relieve low memory pressure.
Looks like the code was even wrong before... if classzone_idx wasn't already set to the highmem zone in the first place, it wouldn't look at it.
> Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
After fixing the bug below,
Acked-by: Vlastimil Babka <vbabka@suse.cz>
> --- > mm/vmscan.c | 32 +++++++++++++++++++------------- > 1 file changed, 19 insertions(+), 13 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index e4f3e068b7a0..6663fc75c3bc 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -3102,24 +3102,30 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx) > > sc.nr_reclaimed = 0; > > - /* Scan from the highest requested zone to dma */ > + /* > + * If the number of buffer_heads in the machine exceeds the > + * maximum allowed level and this node has a highmem zone, > + * force kswapd to reclaim from it to relieve lowmem pressure. > + */ > + if (buffer_heads_over_limit) { > + for (i = MAX_NR_ZONES - 1; i >= 0; i++) {
i--
> + zone = pgdat->node_zones + i; > + if (!populated_zone(zone)) > + continue; > + > + if (is_highmem_idx(i)) > + classzone_idx = i; > + break; > + } > + } > + > + /* Only reclaim if there are no eligible zones */ > for (i = classzone_idx; i >= 0; i--) { > zone = pgdat->node_zones + i; > if (!populated_zone(zone)) > continue; > > - /* > - * If the number of buffer_heads in the machine > - * exceeds the maximum allowed level and this node > - * has a highmem zone, force kswapd to reclaim from > - * it to relieve lowmem pressure. > - */ > - if (buffer_heads_over_limit && is_highmem_idx(i)) { > - classzone_idx = i; > - break; > - } > - > - if (!zone_balanced(zone, order, 0)) { > + if (!zone_balanced(zone, sc.order, classzone_idx)) { > classzone_idx = i; > break; > } >
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