linux-kernel - [PATCH] mm: update the document of numa_zonelist

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Message-ID: <571B1F46.3040805@huawei.com>
Date:	Sat, 23 Apr 2016 15:07:50 +0800
From:	Xishi Qiu <qiuxishi@...wei.com>
To:	Mel Gorman <mgorman@...e.de>, Johannes Weiner <hannes@...xchg.org>,
	"Rik van Riel" <riel@...hat.com>,
	David Rientjes <rientjes@...gle.com>,
	"Kamezawa Hiroyuki" <kamezawa.hiroyu@...fujitsu.com>,
	Fengguang Wu <fengguang.wu@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>
CC:	Linux MM <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH] mm: update the document of numa_zonelist_order

commit 3193913ce62c63056bc67a6ae378beaf494afa66 change the default value
of numa_zonelist_order, this patch update the document.

Signed-off-by: Xishi Qiu <qiuxishi@...wei.com>
---
 Documentation/sysctl/vm.txt |   19 ++++++++++---------
 1 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt
index cb03684..34a5fec 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.
 
 ==============================================================
 
-- 
1.7.1