From: Namjae Jeon <linkinjeon@gmail.com>
To: fengguang.wu@intel.com
Cc: linux-kernel@vger.kernel.org, Namjae Jeon <linkinjeon@gmail.com>,
Namjae Jeon <namjae.jeon@samsung.com>,
Vivek Trivedi <t.vivek@samsung.com>
Subject: [PATCH v3 2/2] Documentation: add description of dirty_background_centisecs
Date: Sun, 16 Sep 2012 08:26:04 -0400 [thread overview]
Message-ID: <1347798364-2864-1-git-send-email-linkinjeon@gmail.com> (raw)
From: Namjae Jeon <namjae.jeon@samsung.com>
This commit adds dirty_background_centisecs description in bdi sysfs
documentation.
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Vivek Trivedi <t.vivek@samsung.com>
---
Documentation/ABI/testing/sysfs-class-bdi | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)
diff --git a/Documentation/ABI/testing/sysfs-class-bdi b/Documentation/ABI/testing/sysfs-class-bdi
index 5f50097..6869736 100644
--- a/Documentation/ABI/testing/sysfs-class-bdi
+++ b/Documentation/ABI/testing/sysfs-class-bdi
@@ -48,3 +48,28 @@ max_ratio (read-write)
most of the write-back cache. For example in case of an NFS
mount that is prone to get stuck, or a FUSE mount which cannot
be trusted to play fair.
+
+dirty_background_centisecs (read-write)
+
+ It is used to start early writeback of given bdi once bdi dirty
+ data exceeds product of average write bandwidth and
+ dirty_background_centisecs. It works in parallel of
+ dirty_writeback_centsecs and dirty_expire_interval based periodic
+ flushing mechanism.
+
+ It is mainly useful for tuning writeback speed at 'NFS Server'
+ sothat NFS client could see better write speed.
+ A good use case is setting it to around 100 (1 second) in the NFS
+ server for improving NFS write performance. Note that it's not
+ recommended to set it to a too small value, which might lead to
+ unnecessary flushing for small IO size.
+ Setting it to 0 disables the feature.
+
+ However, sometimes it may not match user expectations as it is based
+ on bdi write bandwidth estimation. The users should not expect this
+ threshold to work accurately.
+ Write bandwidth estimation is a best effort to estimate bdi write
+ speed bandwidth. But it can be wildly wrong in certain situations
+ such as sudden change of workload (including the workload startup
+ stage), or if there are no heavy writes since boot, in which case
+ there is no reasonable estimation yet.
--
1.7.9.5
next reply other threads:[~2012-09-16 12:26 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-16 12:26 Namjae Jeon [this message]
2012-09-20 8:45 ` [PATCH v3 2/2] Documentation: add description of dirty_background_centisecs Fengguang Wu
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1347798364-2864-1-git-send-email-linkinjeon@gmail.com \
--to=linkinjeon@gmail.com \
--cc=fengguang.wu@intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=namjae.jeon@samsung.com \
--cc=t.vivek@samsung.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).