Messages in this thread | | | Date | Thu, 7 Jul 2016 11:58:09 +0100 | From | Mel Gorman <> | Subject | Re: [PATCH 20/31] mm, vmscan: only wakeup kswapd once per node for the requested classzone |
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On Thu, Jul 07, 2016 at 10:24:23AM +0900, Joonsoo Kim wrote: > On Fri, Jul 01, 2016 at 09:01:28PM +0100, Mel Gorman wrote: > > kswapd is woken when zones are below the low watermark but the wakeup > > decision is not taking the classzone into account. Now that reclaim is > > node-based, it is only required to wake kswapd once per node and only if > > all zones are unbalanced for the requested classzone. > > > > Note that one node might be checked multiple times if the zonelist is > > ordered by node because there is no cheap way of tracking what nodes have > > already been visited. For zone-ordering, each node should be checked only > > once. > > > > Signed-off-by: Mel Gorman <mgorman@techsingularity.net> > > Acked-by: Vlastimil Babka <vbabka@suse.cz> > > --- > > mm/page_alloc.c | 8 ++++++-- > > mm/vmscan.c | 13 +++++++++++-- > > 2 files changed, 17 insertions(+), 4 deletions(-) > > > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > index 441f482bf9a2..2fe2fbb4f2ad 100644 > > --- a/mm/page_alloc.c > > +++ b/mm/page_alloc.c > > @@ -3410,10 +3410,14 @@ static void wake_all_kswapds(unsigned int order, const struct alloc_context *ac) > > { > > struct zoneref *z; > > struct zone *zone; > > + pg_data_t *last_pgdat = NULL; > > > > for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, > > - ac->high_zoneidx, ac->nodemask) > > - wakeup_kswapd(zone, order, ac_classzone_idx(ac)); > > + ac->high_zoneidx, ac->nodemask) { > > + if (last_pgdat != zone->zone_pgdat) > > + wakeup_kswapd(zone, order, ac_classzone_idx(ac)); > > + last_pgdat = zone->zone_pgdat; > > + } > > } > > In wakeup_kswapd(), there is a check if it is a populated zone or not.
It's redundant.
> If first zone in node is not a populated zone, wakeup_kswapd() would be > skipped. Though, I'm not sure if zonelist can include a un-populated > zone.
Zonelists do not contain unpopulated zones.
> Perhaps, moving populated zone check in wakeup_kswapd() to here > would be a safe code. >
If anything was going to happen to it, it should be deleted. It's a minor cleanup.
-- Mel Gorman SUSE Labs
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