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doug
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Message 1158894 - Posted: 5 Oct 2011, 0:46:04 UTC

I watched again as the WUs wound down, distributing work among the idled cores, now that I'm using the Lunatics apps. It behaved exactly as I expected which would explain its 2.5 times speed increase even though I have yet to hit the GPU as far as I can tell. I can't wait to get a ATI GPU task to see how it does. Thanks again to everyone for helping me understand this. I've learned a lot.

Doug

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Message 1158904 - Posted: 5 Oct 2011, 1:19:50 UTC

That's interesting for the first scenario. I've been told but haven't seen it on Linux machines, a single-threaded (or single-CPU) application will be assigned one core/CPU at the start, and will stay on that core/CPU until it finishes or gets interrupted by the CPU scheduling function in the kernel.

Windows will balance the load across all the available cores. 4 cores with a single-threaded task will result in all four cores having ~25% load unless you use task manager to manually set the affinity for that particular process.

I don't know why you experienced the completely idle core issue with the stock setup. I thought the OS kernel was the one that made the scheduling decisions like that, but changing from stock to Lunatics seems to have "fixed" that weird behavior.
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doug
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Message 1158910 - Posted: 5 Oct 2011, 1:33:18 UTC - in response to Message 1158904.

I think Bill Gates had something to do with it. I'm going back to Linux as soon as I can get my internet phone (MagicJack) to work on it or buy a second computer. I've been waiting 2 years.

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Message 1159707 - Posted: 7 Oct 2011, 7:59:04 UTC - in response to Message 1158904.

Actually.....

Under linux I have watched the seti loads get swapped between the cores (3 tasks running on a 4 real core i7). Its seemed to swap every 30 seconds or so, especially jumping to the core that was the coolest and the least active. Quite amusing to watch, which is why I am currently doing the following experiment:


http://setiathome.berkeley.edu/forum_thread.php?id=65352#1159580

My gut instinct is that on such a processor going beyond 6 seti cpu tasks would have minimal to no extra gain - but that's why I am doing the experiment :)

All because I saw the seti tasks being juggled as well as wondering how much spare CPU needs to feed the GPU (nVidia 580 in this case).

Now to get work units flowing so I can really see what it can do lol

Cheers

Mark
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Message boards : Number crunching : Interesting behavior

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