linux-kernel - kernel 2.6.22 CPU shoot up with same amount of file I/O

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Date:	Mon, 19 May 2008 19:47:52 -0700
From:	"Reeve Yang" <reeve.yang@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: kernel 2.6.22 CPU shoot up with same amount of file I/O

Hi all,

We recently upgrade kernel from 2.6.17.4 to 2.6.22.15 on our products.
In our some test, the disk I/O shot as well as CPU utilization, which
starving our some other critical process. For the sake of curiosity, I
ran bonnie++ on both kernels, following are the result:

## ###############Linux 2.6.17 #1 SMP Tue May 6
##################################

Version 1.03c       ------Sequential Output------ --Sequential Input- --Random-
                    -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine        Size       K/sec %CP K/sec %CP K/sec %CP K/sec %CP
K/sec %CP  /sec %CP
ib-10-34-68-2 2016M 23989  35 44123   6 16360   1 21823  28 43090   1 172.7   0
                    ------Sequential Create------ --------Random Create--------
                    -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
              files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
                 16 +++++ +++ +++++ +++ +++++ +++ +++++ +++ +++++ +++ +++++ +++
ib-10-34-68-2.infoblox.com,2016M,23989,35,44123,6,16360,1,21823,28,43090,1,172.7,0,16,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++


## ###############Linux 2.6.22.15 #1 SMP Tue May 6
##################################

bonnie++ -d /storage -s 2016M -u root
                    -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine        Size       K/sec %CP K/sec %CP K/sec %CP K/sec %CP
K/sec %CP  /sec %CP
ib-10-34-68-2 2016M 26078  94 52117  17 23596   5 27172  86 56402   4 160.2   0
                    ------Sequential Create------ --------Random Create--------
                    -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
              files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
                 16 +++++ +++ +++++ +++ +++++ +++ +++++ +++ +++++ +++ +++++ +++
ib-10-34-68-2.infoblox.com,2016M,26078,94,52117,17,23596,5,27172,86,56402,4,160.2,0,16,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++
###################################################################################

As you can see, the I/O throughput improves about 10%, but CPU
utilization is up to 94% from 35% in new and old kernel respectively
for the exact the same test on the exact same hardware system. My
mother board is Tyan S5102 and the CPU is IPentium(R) 4 CPU 3.40GHz. I
searched on the web, some guys suggest to use "highres=off nohz=off
clocksource=acpi-pm" etc., but no help. Has anyone here had similar
problem on  your system? Is this a problem/bug on 2.6.22 kernel?

I saw a patch from Fengguang Wu on this
board(http://lkml.org/lkml/2008/1/15/132). Is this the patch targeting
the above issue? I'd appreciate if anyone could help me out.

Thanks.
- Reeve
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