Daemon or Thread with 5 minute interval
I have been working on a project that analyzes "noise" in Linux clusters running large parallel jobs. Where noise is caused by daemons or kernel threads periodically waking up and slowing down a process of a parallel job enough so that is misses a rendezvous with the other processes and so slows down the entire job. Using an internal tool I have been able to track down several daemons that have been a large source of noise but, after turning them all off I am left with a large noise spike that occurs every 5 minutes. I have tried turning off most of the most common daemons such as cron, ntp, syslog, ect. but, I am still left with this spike. Not being a kernel expert myself I have not been able to experiment with kernel threads. So, my question is does anyone know of a kernel thread or daemon in the 2.4 kernel that wakes up every 5 minutes?
Thanks
Howard
Hi
Can you find the new process's name by getting the ps ax command or Stop the crond and see what happens
Regards
John
----- Original Message -----
From: "Howard Rifkin" <[email protected]>
To: <[email protected]>
Sent: Thursday, May 26, 2005 5:20 PM
Subject: [linux-lvm] Daemon or Thread with 5 minute interval
Quoted 23 lines
I have been working on a project that analyzes "noise" in Linux clusters running large parallel jobs. Where noise is caused by daemons or kernel threads periodically waking up and slowing down a process of a parallel job enough so that is misses a rendezvous with the other processes and so slows down the entire job. Using an internal tool I have been able to track down several daemons that have been a large source of noise but, after turning them all off I am left with a large noise spike that occurs every 5 minutes. I have tried turning off most of the most common daemons such as cron, ntp, syslog, ect. but, I am still left with this spike. Not being a kernel expert myself I have not been able to experiment with kernel threads. So, my question is does anyone know of a kernel thread or daemon in the 2.4 kernel that wakes up every 5 minutes?
Thanks
Howard
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Quoted 2 lines · Howard Rifkin
So, my question is does anyone know of a
kernel thread or daemon in the 2.4 kernel that wakes up every 5 minutes?
[kupdated] can cause massive CPU load if your kernel does not have the IDE chipset support for your system. I think it flushed any data in the HD buffers to disk and if the chipset support isn't there, then the main CPU has
to do this using PIO.
--
Bill
We do have the right kernel support for our didsks. But, you do not need a lot of CPU activity to generate noise. Just enough to disrupt the cashe. Does kupdated run every 5 minutes? If so it could still be the culprit.
Thanks
Howard
Quoted 18 lines · Bill Mair
Quoted 2 lines · Howard Rifkin
So, my question is does anyone know of a
kernel thread or daemon in the 2.4 kernel that wakes up every 5 minutes?[kupdated] can cause massive CPU load if your kernel does not have the IDE chipset support for your system. I think it flushed any data in the HD buffers to disk and if the chipset support isn't there, then the main CPU has
to do this using PIO.Signature · 7 lines
Bill _______________________________________________ linux-lvm mailing list [email protected] https://www.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
Quoted 2 lines · Howard Rifkin
We do have the right kernel support for our didsks. But, you do not need a lot of CPU activity to generate noise. Just enough to disrupt the cashe. Does kupdated run every 5 minutes? If so it could still be the culprit.
kupdated - journal update
kswapd - swapper
bdflush - flush IO
All/any of them could cause problems fir what you are doing, but I don't think LVM is your problem.
--
Bill