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Message-Id: <20070508201904.0ee47ca2.kamezawa.hiroyu@jp.fujitsu.com> Date: Tue, 8 May 2007 20:19:04 +0900 From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org, Lee.Schermerhorn@...com, clameter@....com, akpm@...ux-foundation.org, ak@...e.de, jbarnes@...tuousgeek.org Subject: [PATCH] change zonelist order v5 [3/3] documentation Patch for documentation. Signed-Off-By: KAMEZAWA hiroyuki <kamezawa.hiroyu@...fujitsu.com> --- Documentation/kernel-parameters.txt | 10 +++++++ Documentation/sysctl/vm.txt | 48 ++++++++++++++++++++++++++++++++++++ 2 files changed, 58 insertions(+) Index: linux-2.6.21-mm1/Documentation/kernel-parameters.txt =================================================================== --- linux-2.6.21-mm1.orig/Documentation/kernel-parameters.txt +++ linux-2.6.21-mm1/Documentation/kernel-parameters.txt @@ -1233,6 +1233,16 @@ and is between 256 and 4096 characters. nr_uarts= [SERIAL] maximum number of UARTs to be registered. + numa_zonelist_oder= [KNL,BOOT] + Select zonelist order for NUMA. zonelist is used for + desiding where the kernel allocates memory from. + Default is automatic configuration. If "node" is + specified, zonelist is ordered by locality. This can + offer the best locality but possibility of OOM may + increase. If "zone" is specified, the zonelist is + ordered by zone_type. + See Documentaion/sysctl/vm.txt numa_zonelist_order. + opl3= [HW,OSS] Format: <io> Index: linux-2.6.21-mm1/Documentation/sysctl/vm.txt =================================================================== --- linux-2.6.21-mm1.orig/Documentation/sysctl/vm.txt +++ linux-2.6.21-mm1/Documentation/sysctl/vm.txt @@ -35,6 +35,7 @@ Currently, these files are in /proc/sys/ - stat_interval - readahead_ratio - readahead_hit_rate +- numa_zonelist_order ============================================================== @@ -293,3 +294,49 @@ Possible values can be: The larger value, the more capabilities, with more possible overheads. The default value is 1. + +============================================================== + +numa_zonelist_order + +This sysctl is only for NUMA. +'where the memory is allocated from' is controlled by zonelist. +(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 very robust against OOM of 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. +This will offer the best locality but increases possibility of OOM. +Specify "[Nn]ode" for zone order + +"Zone Order" preserves the DMA zone as long as possible but +results in off-node allocation [for node 0] earlier. +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 a node's DMA zone comprises greater than 60% of its local memory and + the amount of local memory is enough big. + +Otherwise, "zone" order will be selected. Default order is recommended unless +unless this is causing problems for your system/application. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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