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authorXishi Qiu <qiuxishi@huawei.com>2016-04-28 16:19:11 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-04-28 19:34:04 -0700
commit7c88a292dfcd6979e839493ef18d04770eb3bad0 (patch)
tree9e491f3bbb62f99b725af5a633112043ade07248 /Documentation/sysctl/vm.txt
parent33334e25769c6ad69b983379578f42581d99a2f9 (diff)
Documentation/sysctl/vm.txt: update numa_zonelist_order description
Commit 3193913ce62c ("mm: page_alloc: default node-ordering on 64-bit NUMA, zone-ordering on 32-bit") changes the default value of numa_zonelist_order. Update the document. Signed-off-by: Xishi Qiu <qiuxishi@huawei.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Rik van Riel <riel@redhat.com> Cc: David Rientjes <rientjes@google.com> Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/sysctl/vm.txt')
-rw-r--r--Documentation/sysctl/vm.txt19
1 files changed, 10 insertions, 9 deletions
diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt
index cb0368459da3..34a5fece3121 100644
--- a/Documentation/sysctl/vm.txt
+++ b/Documentation/sysctl/vm.txt
@@ -581,15 +581,16 @@ Specify "[Nn]ode" for node order
"Zone Order" orders the zonelists by zone type, then by node within each
zone. Specify "[Zz]one" for zone order.
-Specify "[Dd]efault" to request automatic configuration. Autoconfiguration
-will select "node" order in following case.
-(1) if the DMA zone does not exist or
-(2) if the DMA zone comprises greater than 50% of the available memory or
-(3) if any node's DMA zone comprises greater than 70% of its local memory and
- the amount of local memory is big enough.
-
-Otherwise, "zone" order will be selected. Default order is recommended unless
-this is causing problems for your system/application.
+Specify "[Dd]efault" to request automatic configuration.
+
+On 32-bit, the Normal zone needs to be preserved for allocations accessible
+by the kernel, so "zone" order will be selected.
+
+On 64-bit, devices that require DMA32/DMA are relatively rare, so "node"
+order will be selected.
+
+Default order is recommended unless this is causing problems for your
+system/application.
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