Date: Thu, 2 Jun 2005 09:16:07 -0400 From: Dave Stephens <hsoftdev17@gmail.com> To: freebsd-smp@freebsd.org Subject: Re: Assignmet of CPUs Message-ID: <6845d25a0506020616293991e3@mail.gmail.com> In-Reply-To: <429E67CB.6090901@pacific.net.sg> References: <429E67CB.6090901@pacific.net.sg>
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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@pacific.net.sg> wrote: > Hi, >=20 > it is a general problem of systems with more than one CPU to assign the > proper CPU to a task. >=20 > The most obvious problem is the cache. If a task is migrating all the > time, the cache has to be reloaded again and again. >=20 > 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. >=20 > 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. >=20 > Spreading tasks all over the system with the coolest CPU being the one > to be started next will make systems a bit cooler. >=20 > Erich > _______________________________________________ > freebsd-smp@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-smp > To unsubscribe, send any mail to "freebsd-smp-unsubscribe@freebsd.org" >
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