Documentation for numa_zonelist_order.
Signed-Off-By: KAMEZAWA Hiroyuki <[EMAIL PROTECTED]>
Documentation/kernel-parameters.txt | 5 +++
Documentation/sysctl/vm.txt | 46 ++++++++++++++++++++++++++++++++++++
2 files changed, 51 insertions(+)
Index: linux-2.6.21-mm2/Documentation/sysctl/vm.txt
===================================================================
--- linux-2.6.21-mm2.orig/Documentation/sysctl/vm.txt
+++ linux-2.6.21-mm2/Documentation/sysctl/vm.txt
@@ -33,6 +33,7 @@ Currently, these files are in /proc/sys/
- panic_on_oom
- swap_prefetch
- stat_interval
+- numa_zonelist_order
==============================================================
@@ -248,3 +249,48 @@ determines the frequency of these consol
The default value is 1 second.
+==============================================================
+
+numa_zonelist_order
+
+This sysctl is only for NUMA.
+'where the memory is allocated from' is controlled by zonelists.
+(This documentation ignores ZONE_HIGHMEM/ZONE_DMA32 for simple explanation.
+ you may be able to read ZONE_DMA as ZONE_DMA32...)
+
+In non-NUMA case, a zonelist for GFP_KERNEL is ordered as following.
+ZONE_NORMAL -> ZONE_DMA
+This means that a memory allocation request for GFP_KERNEL will
+get memory from ZONE_DMA only when ZONE_NORMAL is not available.
+
+In NUMA case, you can think of following 2 types of order.
+Assume 2 node NUMA and below is zonelist of Node(0)'s GFP_KERNEL
+
+(A) Node(0) ZONE_NORMAL -> Node(0) ZONE_DMA -> Node(1) ZONE_NORMAL
+(B) Node(0) ZONE_NORMAL -> Node(1) ZONE_NORMAL -> Node(0) ZONE_DMA.
+
+Type(A) offers the best locality for processes on Node(0), but ZONE_DMA
+will be used before ZONE_NORMAL exhaustion. This increases possibility of
+out-of-memory(OOM) of ZONE_DMA because ZONE_DMA is tend to be small.
+
+Type(B) cannot offer the best locality but is more robust against OOM of
+the DMA zone.
+
+Type(A) is called as "Node" order. Type (B) is "Zone" order.
+
+"Node order" orders the zonelists by node, then by zone within each node.
+Specify "[Nn]ode" for zone order
+
+"Zone Order" orders the zonelists by zone type, then by node within each
+zone. Specify "[Zz]one"for zode 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 60% 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.
+
Index: linux-2.6.21-mm2/Documentation/kernel-parameters.txt
===================================================================
--- linux-2.6.21-mm2.orig/Documentation/kernel-parameters.txt
+++ linux-2.6.21-mm2/Documentation/kernel-parameters.txt
@@ -1231,6 +1231,11 @@ and is between 256 and 4096 characters.
nowb [ARM]
+ numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
+ one of ['zone', 'node', 'default'] can be specified
+ This can be set from sysctl after boot.
+ See Documentation/sysctl/vm.txt for details.
+
nr_uarts= [SERIAL] maximum number of UARTs to be registered.
opl3= [HW,OSS]
-
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