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List:       kde-devel
Subject:    Re: CPU load control
From:       Henry Miller <hank () millerfarm ! com>
Date:       2005-08-17 3:58:05
Message-ID: 200508162258.06901.hank () millerfarm ! com
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On Tuesday 16 August 2005 10:24 pm, Manuel Amador wrote:
> In my opinion, at load average ~ 1 is when the system feels fully
> responsive, above that you begin to feel that the system is "not as
> responsive as before".
>
> Load at 2, and the system starts to feel like it cannot be used.  Over
> here, from 2 up people start to ask "Is the server slow?" (we run a
> terminal server, so it's pretty important to keep load low).

What operating system, how many CPUs, and what priority are the other 
processes running at?   On my dual processor machine a load of 1 means that 
one CPU is sitting idle.   If I had a 64 processor machine, then a load of 60 
would be perfect acceptable.

Some systems handle load better than others.   I've had a load > 4 on my 
FreeBSD machine, and it was useable, while my linux machine wasn't.   (Note, 
invalid comparison, the linux machine was a 386 running a 2.0.x kernel, while 
the FreeBSD machine is an Athalon 1 ghz, with a 5.x kernel) 

> It all depends on what level of interactive responsiveness you're
> aiming.  An indexing daemon should, IMO, throttle as soon as the system
> begins to feel lagging, even if just a bit.  That's why I recommend
> loadavg = 1.

No, it should run at a low priority, one above idle.  (We want to be higher 
than distributed.net clients, but lower than everything else).    A good OS 
scheduler should have no problem preventing the indexer from interfering with 
active users.

> > Speaking of arts, arts _does_ load average monitoring and bails on CPU
> > overload (it assumes any CPU overload is its own fault), so you could
> > take a look at what code is in there.

which isn't a good idea, but if there are bugs in aRts it might be all we can 
do.    It fails when there are several processors kept busy enough that you 
have the right amount of CPUs.

Dual-core is already here on the high end, and multi-processor systems are old 
news.    It won't be long as the average KDE user will have more than one 
processor.   Anything that doesn't account for this will be problems.


 
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