From fc1ca3d5b4b9532fff76fa21f7d22efdf02d38b7 Mon Sep 17 00:00:00 2001
From: Yang Shi <yang.shi@linux.alibaba.com>
Date: Tue, 19 Jun 2018 07:59:18 +0800
Subject: [PATCH] doc: add description to dirtytime_expire_seconds
commit 1efff914afac8a965ad63817ecf8861a927c2ace ("fs: add
dirtytime_expire_seconds sysctl") introduced dirtytime_expire_seconds
knob, but there is not description about it in
Documentation/sysctl/vm.txt.
Add the description for it.
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
---
Documentation/sysctl/vm.txt | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt
index 697ef8c225dfa..960e82759ffb5 100644
--- a/Documentation/sysctl/vm.txt
+++ b/Documentation/sysctl/vm.txt
@@ -27,6 +27,7 @@ Currently, these files are in /proc/sys/vm:
- dirty_bytes
- dirty_expire_centisecs
- dirty_ratio
+- dirtytime_expire_seconds
- dirty_writeback_centisecs
- drop_caches
- extfrag_threshold
@@ -178,6 +179,18 @@ The total available memory is not equal to total system memory.
==============================================================
+dirtytime_expire_seconds
+
+When a lazytime inode is constantly having its pages dirtied, the inode with
+an updated timestamp will never get chance to be written out. And, if the
+only thing that has happened on the file system is a dirtytime inode caused
+by an atime update, a worker will be scheduled to make sure that inode
+eventually gets pushed out to disk. This tunable is used to define when dirty
+inode is old enough to be eligible for writeback by the kernel flusher threads.
+And, it is also used as the interval to wakeup dirtytime_writeback thread.
+
+==============================================================
+
dirty_writeback_centisecs
The kernel flusher threads will periodically wake up and write `old' data
--
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