linux-kernel - [PATCH 3/3] sysctl/vm.txt: Update document

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Date:   Fri, 15 Sep 2017 17:23:26 +0800
From:   Kemi Wang <kemi.wang@...el.com>
To:     "Luis R . Rodriguez" <mcgrof@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jonathan Corbet <corbet@....net>,
        Michal Hocko <mhocko@...e.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Johannes Weiner <hannes@...xchg.org>,
        Christopher Lameter <cl@...ux.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Vlastimil Babka <vbabka@...e.cz>,
        Hillf Danton <hillf.zj@...baba-inc.com>
Cc:     Dave <dave.hansen@...ux.intel.com>,
        Tim Chen <tim.c.chen@...el.com>,
        Andi Kleen <andi.kleen@...el.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Ying Huang <ying.huang@...el.com>,
        Aaron Lu <aaron.lu@...el.com>, Kemi Wang <kemi.wang@...el.com>,
        Proc sysctl <linux-fsdevel@...r.kernel.org>,
        Linux MM <linux-mm@...ck.org>,
        Linux Kernel <linux-kernel@...r.kernel.org>
Subject: [PATCH 3/3] sysctl/vm.txt: Update document

Add a paragraph to introduce the functionality and usage on vmstat_mode in
sysctl/vm.txt

Reported-by: Jesper Dangaard Brouer <brouer@...hat.com>
Suggested-by: Dave Hansen <dave.hansen@...el.com>
Suggested-by: Ying Huang <ying.huang@...el.com>
Signed-off-by: Kemi Wang <kemi.wang@...el.com>
---
 Documentation/sysctl/vm.txt | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt
index 9baf66a..6ab2843 100644
--- a/Documentation/sysctl/vm.txt
+++ b/Documentation/sysctl/vm.txt
@@ -61,6 +61,7 @@ Currently, these files are in /proc/sys/vm:
 - swappiness
 - user_reserve_kbytes
 - vfs_cache_pressure
+- vmstat_mode
 - watermark_scale_factor
 - zone_reclaim_mode
 
@@ -843,6 +844,31 @@ ten times more freeable objects than there are.
 
 =============================================================
 
+vmstat_mode
+
+This interface allows virtual memory statistics configurable.
+
+When performance becomes a bottleneck and you can tolerate some possible
+tool breakage and some decreased counter precision (e.g. numa counter), you
+can do:
+	echo [C|c]oarse > /proc/sys/vm/vmstat_mode
+ignorable statistics list:
+- numa counters
+
+When performance is not a bottleneck and you want all tooling to work, you
+can do:
+	echo [S|s]trict > /proc/sys/vm/vmstat_mode
+
+We recommend automatic detection of virtual memory statistics by system,
+this is also system default configuration, you can do:
+	echo [A|a]uto > /proc/sys/vm/vmstat_mode
+
+E.g. numa statistics does not affect system's decision and it is very
+rarely consumed. If set vmstat_mode = auto, numa counters update is skipped
+unless the counter is *read* by users at least once.
+
+==============================================================
+
 watermark_scale_factor:
 
 This factor controls the aggressiveness of kswapd. It defines the
-- 
2.7.4