Messages in this thread | | | Date | Thu, 5 Apr 2018 09:57:53 +0200 | From | Michal Hocko <> | Subject | Re: [PATCH] mm/thp: don't count ZONE_MOVABLE as the target for freepage reserving |
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On Thu 05-04-18 16:27:16, Joonsoo Kim wrote: > From: Joonsoo Kim <iamjoonsoo.kim@lge.com> > > ZONE_MOVABLE only has movable pages so we don't need to keep enough > freepages to avoid or deal with fragmentation. So, don't count it. > > This changes min_free_kbytes and thus min_watermark greatly > if ZONE_MOVABLE is used. It will make the user uses more memory.
OK, but why does it matter. Has anybody seen this as an issue?
> o System > 22GB ram, fakenuma, 2 nodes. 5 zones are used. > > o Before > min_free_kbytes: 112640 > > zone_info (min_watermark): > Node 0, zone DMA > min 19 > Node 0, zone DMA32 > min 3778 > Node 0, zone Normal > min 10191 > Node 0, zone Movable > min 0 > Node 0, zone Device > min 0 > Node 1, zone DMA > min 0 > Node 1, zone DMA32 > min 0 > Node 1, zone Normal > min 14043 > Node 1, zone Movable > min 127 > Node 1, zone Device > min 0 > > o After > min_free_kbytes: 90112 > > zone_info (min_watermark): > Node 0, zone DMA > min 15 > Node 0, zone DMA32 > min 3022 > Node 0, zone Normal > min 8152 > Node 0, zone Movable > min 0 > Node 0, zone Device > min 0 > Node 1, zone DMA > min 0 > Node 1, zone DMA32 > min 0 > Node 1, zone Normal > min 11234 > Node 1, zone Movable > min 102 > Node 1, zone Device > min 0 > > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> > --- > mm/khugepaged.c | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index 5de1c6f..92dd4e6 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -1880,8 +1880,16 @@ static void set_recommended_min_free_kbytes(void) > int nr_zones = 0; > unsigned long recommended_min; > > - for_each_populated_zone(zone) > + for_each_populated_zone(zone) { > + /* > + * We don't need to worry about fragmentation of > + * ZONE_MOVABLE since it only has movable pages. > + */ > + if (zone_idx(zone) > gfp_zone(GFP_USER)) > + continue; > + > nr_zones++; > + } > > /* Ensure 2 pageblocks are free to assist fragmentation avoidance */ > recommended_min = pageblock_nr_pages * nr_zones * 2; > -- > 2.7.4 >
-- Michal Hocko SUSE Labs
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