From mboxrd@z Thu Jan 1 00:00:00 1970
From: bugzilla-daemon@bugzilla.kernel.org
Subject: [Bug 71641] New: Unreasonable performance degradation in ext4 with
full data journaling
Date: Fri, 07 Mar 2014 11:39:40 +0000
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https://bugzilla.kernel.org/show_bug.cgi?id=3D71641
Bug ID: 71641
Summary: Unreasonable performance degradation in ext4 with f=
ull
data journaling
Product: File System
Version: 2.5
Kernel Version: 3.4.6
Hardware: x86-64
OS: Linux
Tree: Mainline
Status: NEW
Severity: normal
Priority: P1
Component: ext4
Assignee: fs_ext4@kernel-bugs.osdl.org
Reporter: fredchang.tc@gmail.com
Regression: No
JFS provides three modes, journal, ordered and writeback.
The first mode is denoted as =E2=80=98journal mode=E2=80=99in the follo=
wing context.
In the journal mode, data should be written twice, one for the journal =
area and
the other for the client file system. If the journal area and the clien=
t file
system are both located in the disk, it has at least 50% performance
degradation compared to ordered mode.
But what if we put the journal area in a ramdisk?
I did the following tests. It shows the ext4 with full data journaling =
has
unreasonable performance degradation even the journal area is located i=
n the
ramdisk.
Test environment-- =20
CPU: Intel(R) Xeon(R) CPU E3-1225 v3 @ 3.20GHz
RAM:8GB
=46ilesystem:Ext4
Linux version:3.4.6
RAID are composed of 6 x 1TB HD
Command: time dd if=3D/dev/zero of=3D Write_File bs=3D1M count=3D51200
Volume_type ordered_mode Journal_mode degradation
Single_disk 173MB/s 144MB/s 17%
RAID0 937MB/s 375MB/s 60%
RAID5 732MB/s 132MB/s 82%
Does anyone know where the bottleneck may be?
--=20
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