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authorIngo Molnar <mingo@kernel.org>2016-05-05 10:12:37 +0200
committerIngo Molnar <mingo@kernel.org>2016-05-05 10:12:37 +0200
commit1a618c2cfe4c02190d8d1f9c5052f0defc58de20 (patch)
tree170002288786f702e1d4ca638b53d1594a7caa16 /Documentation/sysctl
parent03d85a63ee3e2d3a43460f936b86334b32f88c89 (diff)
parent8482716b9d865db34c55d4bf2fed19498e7195b9 (diff)
downloadlinux-1a618c2cfe4c02190d8d1f9c5052f0defc58de20.tar.bz2
Merge branch 'perf/urgent' into perf/core, to pick up fixes
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'Documentation/sysctl')
-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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