Assignmet of CPUs

Dave Stephens hsoftdev17 at gmail.com
Thu Jun 2 06:16:55 PDT 2005


The main problem I see with using temperature is that the ability to
detect CPU temp. is a feature limited to "more modern" machines.  It
has become very common even in desktops now a days, but it wouldn't be
available in legacy hardware or custom hardware.

Just a thought.


On 6/1/05, Erich Dollansky <oceanare at pacific.net.sg> wrote:
> Hi,
> 
> it is a general problem of systems with more than one CPU to assign the
> proper CPU to a task.
> 
> The most obvious problem is the cache. If a task is migrating all the
> time, the cache has to be reloaded again and again.
> 
> The next problem is the location of the data in RAM on NUMA machines. It
> is better to leave a thread on a CPU if the RAM connected to it also has
> the data stored. This could block a task from running if to many running
> tasks have their data stored on the same CPU.
> 
> The last, but hardly used parameter, is the CPU temperature. I noticed
> that FreeBSD tends to use always the same CPU to start a task. This
> makes one CPU real hot while the other stays cool. Taking the CPU
> temperature into account for starting at least new threads would also
> have an advantage of systems with an less then ideal cooling system.
> 
> Spreading tasks all over the system with the coolest CPU being the one
> to be started next will make systems a bit cooler.
> 
> Erich
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