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authorMel Gorman <mgorman@techsingularity.net>2016-09-02 02:14:55 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2016-09-02 03:52:01 +0300
commit6aa303defb7454a2520c4ddcdf6b081f62a15890 (patch)
treef29799a63374ed8b39114c8f55bc10f52b679737 /include/linux/mmzone.h
parente6173ba42bbdba05fd4f3021c0beda0506271507 (diff)
downloadlinux-6aa303defb7454a2520c4ddcdf6b081f62a15890.tar.xz
mm, vmscan: only allocate and reclaim from zones with pages managed by the buddy allocator
Firmware Assisted Dump (FA_DUMP) on ppc64 reserves substantial amounts of memory when booting a secondary kernel. Srikar Dronamraju reported that multiple nodes may have no memory managed by the buddy allocator but still return true for populated_zone(). Commit 1d82de618ddd ("mm, vmscan: make kswapd reclaim in terms of nodes") was reported to cause kswapd to spin at 100% CPU usage when fadump was enabled. The old code happened to deal with the situation of a populated node with zero free pages by co-incidence but the current code tries to reclaim populated zones without realising that is impossible. We cannot just convert populated_zone() as many existing users really need to check for present_pages. This patch introduces a managed_zone() helper and uses it in the few cases where it is critical that the check is made for managed pages -- zonelist construction and page reclaim. Link: http://lkml.kernel.org/r/20160831195104.GB8119@techsingularity.net Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Reported-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Tested-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Acked-by: Michal Hocko <mhocko@suse.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/mmzone.h')
-rw-r--r--include/linux/mmzone.h16
1 files changed, 14 insertions, 2 deletions
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index d572b78b65e1..7f2ae99e5daf 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -828,9 +828,21 @@ unsigned long __init node_memmap_size_bytes(int, unsigned long, unsigned long);
*/
#define zone_idx(zone) ((zone) - (zone)->zone_pgdat->node_zones)
-static inline int populated_zone(struct zone *zone)
+/*
+ * Returns true if a zone has pages managed by the buddy allocator.
+ * All the reclaim decisions have to use this function rather than
+ * populated_zone(). If the whole zone is reserved then we can easily
+ * end up with populated_zone() && !managed_zone().
+ */
+static inline bool managed_zone(struct zone *zone)
+{
+ return zone->managed_pages;
+}
+
+/* Returns true if a zone has memory */
+static inline bool populated_zone(struct zone *zone)
{
- return (!!zone->present_pages);
+ return zone->present_pages;
}
extern int movable_zone;