mm/thp: don't count ZONE_MOVABLE as the target for freepage reserving
There was a regression report for "mm/cma: manage the memory of the CMA area by using the ZONE_MOVABLE" [1] and I think that it is related to this problem. CMA patchset makes the system use one more zone (ZONE_MOVABLE) and then increases min_free_kbytes. It reduces usable memory and it could cause regression. 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. System: 22GB ram, fakenuma, 2 nodes. 5 zones are used. 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 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 [1] (lkml.kernel.org/r/20180102063528.GG30397%20()%20yexl-desktop) Link: http://lkml.kernel.org/r/1522913236-15776-1-git-send-email-iamjoonsoo.kim@lge.com Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -1879,8 +1879,16 @@ static void set_recommended_min_free_kbytes(void)
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int nr_zones = 0;
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unsigned long recommended_min;
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for_each_populated_zone(zone)
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for_each_populated_zone(zone) {
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/*
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* We don't need to worry about fragmentation of
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* ZONE_MOVABLE since it only has movable pages.
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*/
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if (zone_idx(zone) > gfp_zone(GFP_USER))
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continue;
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nr_zones++;
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}
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/* Ensure 2 pageblocks are free to assist fragmentation avoidance */
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recommended_min = pageblock_nr_pages * nr_zones * 2;
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