Re: Hello and a question about high cpu usage on jfsCommit (kernel2.6.25.1)

From: David Fix
Date: Tue May 20 2008 - 09:06:24 EST

Hey Dave,

Thanks for following up on this... The previous kernel that I was running was From CentOS 5.1.

It appears that the thread eating up that much CPU isn't a continuous happening, only when there's a fair amount of activity going on. It's hard to nail down exactly when it happens, but the next time it does, I'll definitely let you all know!

I haven't been able to reboot this machine, as it's a production unit, but if I do get the chance, I'll do so. It seems to have leveled out now, with there being no high usage at all on there right now.


Dave Kleikamp wrote:
I'm copying this to jfs-discussion to see if anyone has seen anything
like this.

On Thu, 2008-05-15 at 15:35 -0400, David Fix wrote:
Hey guys,

I'm new to the list, but I've been using Linux and fooling around with the kernel for ages. :)

I've been experiencing high CPU usage for jfsCommit on kernel (haven't had a chance to go to, but I didn't see any JFS-specific changes between the versions yet).

In fact, there haven't been a whole lot of non-cosmetic changes to jfs
at all recently. Nothing I see that suspicious.

What was the previous kernel you were running before moving to

Here's my hardware config, as well:

CPUs: 2x Intel Xeon E5420 2.5GHz Quad-core
RAID Controller: 3Ware 9650SE-24M8

For anyone seeing this for the first time on jfs-discussion, Dave
followed up stating that this was an x86_64 build.

I can't find a mention of what motherboard I have in here, so I'll give a bit of lspci:

00:00.0 Host bridge: Intel Corporation 5000P Chipset Memory Controller Hub (rev b1)
00:1d.0 USB Controller: Intel Corporation 631xESB/632xESB/3100 Chipset UHCI USB Controller #1 (rev 09)
00:1e.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev d9)
01:00.0 PCI bridge: Intel Corporation 6311ESB/6321ESB PCI Express Upstream Port (rev 01)
03:00.0 PCI bridge: Integrated Device Technology, Inc. Unknown device 8018 (rev 04) (prog-if 00 [Normal decode])
05:00.0 Ethernet controller: Intel Corporation 82571EB Gigabit Ethernet Controller (rev 06)
07:00.0 Ethernet controller: Intel Corporation 80003ES2LAN Gigabit Ethernet Controller (Copper) (rev 01)
0c:00.0 RAID bus controller: 3ware Inc 9650SE SATA-II RAID (rev 01)
0f:0c.0 VGA compatible controller: ATI Technologies Inc ES1000 (rev 02)

There's the salient points there. The NIC is a quad, which is trunked to the switch using LAPC.

I've got a RAID-6 on the 3Ware controller of 20 TB, and when I'm running "top", I see this:

top - 15:33:27 up 5:40, 3 users, load average: 4.33, 3.59, 3.98
Tasks: 315 total, 2 running, 313 sleeping, 0 stopped, 0 zombie
Cpu(s): 0.2%us, 13.2%sy, 0.0%ni, 61.3%id, 24.9%wa, 0.1%hi, 0.2%si, 0.0%st
Mem: 8194264k total, 8144500k used, 49764k free, 3884k buffers
Swap: 16779884k total, 148k used, 16779736k free, 7667400k cached

2669 root 15 -5 0 0 0 R 99 0.0 19:45.71 jfsCommit

This is highly unusual. Is this thread continually eating cpu at this
rate, or does it happen in spurts?

And people are complaining (and I'm seeing) very slow writes to the drives.

Just wondering if anyone has any ideas. :) If you need any information, I'll provide whatever you need.

Has this happened more than once (have you rebooted and still seen the
problem)? I'm not sure if some rare bug has caused some kind of linked
list corruption that puts the thread into an infinite loop, or if this
is a real regression.

Thanks in advance!



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