Re: Bouts of Extreme System Slug

Hello Tim, All,

Apparently, my problem was heating related. My laptop is sitting on
a table with an uneven plastic table cloth, and since I raised it
slightly up from the table by putting bottle caps under the rear feet,
I have not experienced any problems any more.

The connection between heat and sluggishness was not that obvious.
Before the raising, I had installed temperature displays, and when I
run at full load, the temperature would first go up to 90-something,
then fall again, and only after that it would start to slow down. If
the slowing down is from a deliberate slowdown to decrease
temperature, the response seem to come too late and to strong.

Take care
Oliver

On Wed, Apr 1, 2009 at 12:00 PM, Tim <ignored_mailbox@xxxxxxxxxxxx> wrote:
Tim:
Is the CPU cooling still working fine?  Overheating can cause slowdowns.

Oliver Ruebenacker:
  Interesting! How can I test this?

Does the fan move air well, is it clogged, can you visually inspect it,
does the temperature change if you *VERY* *BRIEFLY* block airflow.

Do you know what mechanism causes the slowdown?

Most modern CPUs have a temperature sensor.  As a self preservation
exercise, many will slow down operations if they start to get too hot,
as that will reduce the amount of heat the CPU produces.

 Is it consistent with showing high CPU usage?

If the CPU is doing a lot of work, or running fast (for those that have
speed control), it will generate heat.  The more work and speed, the
more heat.  Also, in one of life's peculiarities, if slowing down the
CPU means it takes significantly longer to get the job done, slowing it
down mightn't be the life saver that it's supposed to be, as it may
still get hot enough, for long enough, to be a problem.

With really inadequate cooling, you can fry things in mere seconds.  I
got quite worried when my laptop suddenly went nuts the other day, for
no good reason.  Typically, it's running around the 50 degree mark for
both CPU and graphics processors, but it surges depending on the work
load, often to around 60 (it used to be about 5-10 degrees less, and I
can reproduce that by swapping the hard drive for the old one that still
has Fedora 7 on it).  I loaded up some webpage, and it rapidly
skyrocketed to 80, the fan turned on hard, and some rather nasty smells
emerged.  I'm guessing plastic nearby the hotspot, or heatsink material.
I killed the Firefox web browser smartish, and it settled down to a
reasonable temperature within a few seconds.  No the vents were not
blocked, and I have checked for things that might clog airflow.

It strikes me that many laptops are very poorly designed, with air
intake vents on the bottom, that will be blocked if you actually do use
it on your lap.

  Actually, I also felt sometimes that my laptop was quite hot, long
before I had slowdown issues. And sometimes the fan would seem to gear
up, even with no one using the laptop.

Mine used to run quite cool and quiet, but not since Fedora 9.  Just
sitting at the logon screen its churning away.  So I have yet another
thing I don't like about the new GDM (it's not just spinning the fans
more than needed, they're expelling quite a bit of heat).

If I logon and do nothing, it cools down a bit, sometimes enough that it
runs nearly silently; but that's rare, these days.  But, if I leave it
alone, and it's idling just showing the empty desktop (no applications
running), sometimes it'll suddenly warm up.  And it's not like a cron
job has kicked in, there's no indication of that if I leave top running.

--
[tim@localhost ~]$ uname -r
2.6.27.19-78.2.30.fc9.i686

Don't send private replies to my address, the mailbox is ignored.  I
read messages from the public lists.



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--
Oliver Ruebenacker, Computational Cell Biologist
BioPAX Integration at Virtual Cell (http://vcell.org/biopax)
Center for Cell Analysis and Modeling
http://www.oliver.curiousworld.org

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