Re: [SLUG] slowdown

From: steve szmidt (steve@szmidt.org)
Date: Tue Feb 12 2008 - 16:22:02 EST


On Tuesday 12 February 2008, Eben King wrote:
> Something's using up CPU time on my machine, but nothing shows in top nor
> gkrellm's strip charts, nor does any unusual network use show up in
> gkrellm. But bash and trn take seconds to start and exit, and the CPU speed
> is a constant 2.4G (normally it falls back when nothing's happening). How
> can I find out what it is? I can get network bandwidth from the
> internet-facing router for everyone combined (which is mostly me), for
> periods from 1m - 5h.

If an application does not thread and ties up some h/w you also get these
dragged out delays. A similar thing can be seen with the desktop. Start
something which opens a login or confirmation window and leave it alone.
Other confirmation windows ends up in a queue waiting for the first to be
cleared.

Windows does that on boot when it looks for drives. It will sit and time out
on every drive, rather than running multiple threads and do all drives. No
doubt some nasty design hole which they cannot get around do to overly
complex code.

When you say it's using up your CPU how do you identify this?

Often times a machine look like it has locked up but is actually in some deep
processing which is using up some resource making the desktop appear locked
up.

Unlike windows all running processes will show up on top. Nor do I think top
lies. Remember, today's computers have more processing going on than in your
CPU. You have a number of controllers that all do their processing. If anyone
of them is busy another request will end up in a queue.

This is an example where top will show you low CPU load but heavy system load.
The system load, or load average, is a loose indicator of overall system load.
Basically 1.00 is ideal top load per core. In theory if you go above that
there are processes being queued as they are more than what can be
processed "realtime." It is however a non scientific measurement. Obviously
it have survived for a long time so it is a popular yardstick.

-- 

Steve Szmidt

"They that would give up essential liberty for temporary safety deserve neither liberty nor safety." Benjamin Franklin ----------------------------------------------------------------------- This list is provided as an unmoderated internet service by Networked Knowledge Systems (NKS). Views and opinions expressed in messages posted are those of the author and do not necessarily reflect the official policy or position of NKS or any of its employees.



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