Freeing CPU cores

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bill

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Message 1400614 - Posted: 8 Aug 2013, 13:44:26 UTC

Has anyone posted the exact meaning of 'freeing up
a cpu core' in relation to gpu usage, and the where
and how to do so? And since there is more than one
way to do it, which would be the best/easiest/fastest
way to do it, in such a way that a newb would understand
it? A faq perhaps?
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Message 1400634 - Posted: 8 Aug 2013, 14:25:04 UTC - in response to Message 1400614.  

Has anyone posted the exact meaning of 'freeing up
a cpu core' in relation to gpu usage, and the where
and how to do so? And since there is more than one
way to do it, which would be the best/easiest/fastest
way to do it, in such a way that a newb would understand
it? A faq perhaps?


I 'free up a core' in the local Preferences>processor usage tab. "On multiprocessor systems, use at most ___% of the processors."

I set mine at 90% and it crunches on 7 cores and leaves the 8th free.
75% on a 4 core system will leave 1 free

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Message 1400639 - Posted: 8 Aug 2013, 15:09:52 UTC - in response to Message 1400634.  

Yes, but is that for ATI or NVIDIA or is there a difference
between the two that newbs should be aware of.

Mine are set. I'm looking for something to point to when
a newb comes in that can be pointed at to answer their questions
while inflicting the minimum of pain on them.
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Message 1400659 - Posted: 8 Aug 2013, 15:48:23 UTC - in response to Message 1400639.  
Last modified: 8 Aug 2013, 15:50:05 UTC

Yes, but is that for ATI or NVIDIA or is there a difference
between the two that newbs should be aware of.

Mine are set. I'm looking for something to point to when
a newb comes in that can be pointed at to answer their questions
while inflicting the minimum of pain on them.


Works for both.

90% doesn`t free a full core.
On a 8 core the correct settings is 86% on a quad 75%.


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Message 1400663 - Posted: 8 Aug 2013, 15:58:27 UTC - in response to Message 1400639.  
Last modified: 8 Aug 2013, 16:01:48 UTC

Yes, but is that for ATI or NVIDIA or is there a difference
between the two that newbs should be aware of.

The unwrited rules is...
You need to free 1 core if you have a AMD CPU and want to crunch on the GPU (ATI or NV) even if you run only MB, if you run AP you need to add +1 free core per GPU WU (AMD or Intel CPU).

To be sure the % to use just do the following math: 100*(1-(free cores needed)/(processor number of cores))

On I5 or Quad a processor number of cores = 4
On I7 processor number of cores =8 without HT or 4 with HT enabled
Same works with AMD or other Intels CPU´s.

It´s clear now?
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Message 1400673 - Posted: 8 Aug 2013, 16:33:52 UTC

With 8 cores one core is 12.5.

Anything less than 100 will free one core. (allow 7 tasks)
88 will free one core. (7 tasks)
87.5 - since it's allow' One core not used - 7 tasks
87 will free two cores.
80 - 6 out of 8 cores in use
75 - still 6
74 - 5
70 - 5

So, for ease of editing when you have 8 cores:

50 - 4 cores used
70 - 5 cores used
80 - 6 cores used
90 - 7 cores used

And for a quad:

50 - 2 cores
75 - 3 cores (you could use 80 too)


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Message 1400675 - Posted: 8 Aug 2013, 16:40:01 UTC
Last modified: 8 Aug 2013, 17:19:50 UTC

edited


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Message 1400677 - Posted: 8 Aug 2013, 16:42:53 UTC - in response to Message 1400675.  

On a AMD CPU 88% isn`t enough.
At least on a FX 86% is needed.

86 should be freeing two cores - if you have more than 6 CPU tasks running, you've found a bug.
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Message 1400680 - Posted: 8 Aug 2013, 16:50:57 UTC - in response to Message 1400677.  
Last modified: 8 Aug 2013, 17:19:31 UTC

[quote]


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Message 1400682 - Posted: 8 Aug 2013, 16:52:56 UTC - in response to Message 1400677.  
Last modified: 8 Aug 2013, 16:53:45 UTC

On a AMD CPU 88% isn`t enough.
At least on a FX 86% is needed.

86 should be freeing two cores - if you have more than 6 CPU tasks running, you've found a bug.


My FX 8150 is set to use 90% and it's crunching 7:
08/08/2013 11:13:54 AM | | max CPUs used: 7

One core should be enough for 2 GTX 560 with 2 wu's each, shouldn't it? The work times are similar to the GTX 560 in my other machine that has a free core (Phenom 9650) and 2 wu's. -- ONLY MB btw.
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Message 1400685 - Posted: 8 Aug 2013, 17:01:36 UTC - in response to Message 1400680.  

On a AMD CPU 88% isn`t enough.
At least on a FX 86% is needed.

86 should be freeing two cores - if you have more than 6 CPU tasks running, you've found a bug.


More than one actually LOL.

Windows assigns upt to 13.5% to one CPU core.
So if you only reseverve 88% no full core is available.
This depends on the Win work scheduler.

I`ve tested this excessive in the last 2 years.

Well what BOINC does and what Windows does are different things.
88 will tell boinc to only run 7 tasks, 87 drops it to 6 tasks.

Those 7 cores will be fully used (depending on app) the remaining core then takes the normal load - so yes, technically not a full core is available.

For most people freeing most of a CPU core is enough.

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Message 1400686 - Posted: 8 Aug 2013, 17:03:17 UTC - in response to Message 1400682.  
Last modified: 8 Aug 2013, 17:19:13 UTC

[quote]


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Message 1400687 - Posted: 8 Aug 2013, 17:05:46 UTC - in response to Message 1400685.  
Last modified: 8 Aug 2013, 17:18:52 UTC

edited


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Message 1400688 - Posted: 8 Aug 2013, 17:06:05 UTC - in response to Message 1400682.  

On a AMD CPU 88% isn`t enough.
At least on a FX 86% is needed.

86 should be freeing two cores - if you have more than 6 CPU tasks running, you've found a bug.


My FX 8150 is set to use 90% and it's crunching 7:
08/08/2013 11:13:54 AM | | max CPUs used: 7

One core should be enough for 2 GTX 560 with 2 wu's each, shouldn't it? The work times are similar to the GTX 560 in my other machine that has a free core (Phenom 9650) and 2 wu's. -- ONLY MB btw.


Rule of thumb is one core per card. - You might want to try and free another core.

We've gone horribly offtopic by the way which is quite impolite to a new user. Where's a moderator when you need one...
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Message 1400691 - Posted: 8 Aug 2013, 17:12:00 UTC - in response to Message 1400688.  
Last modified: 8 Aug 2013, 17:18:15 UTC

[quote]


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Message 1400697 - Posted: 8 Aug 2013, 17:23:25 UTC

I suspect what I'm doing is different from almost everyone else:

I use the anonymous platform, not stock apps, so I can use app_info.xml.

In BOINC my settings are to use 100% of the CPU.

In app_info, for astropulse I set <avg_ncpus> and <max_ncpus> to 1, so it sets aside a core for each GPU job when they run.

For multibeam I don't free a core, I use the command line settings:

-cpu_lock -instances_per_device 2 -gpu_lock

which set the GPU jobs to run on an assigned single core. For my Phenom II, at least, that works as well as idling a core.
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Message 1400704 - Posted: 8 Aug 2013, 17:27:54 UTC

To answer the original question: if anyone writes a FAQ entry I'll be delighted to post it in the Lunatics FAQ section.
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Message 1400755 - Posted: 8 Aug 2013, 19:04:05 UTC

I am just days away from trying to get my first AMD graphics card going on a rig.

Is freeing up a core something I only need to worry about for AMD cards? So far with NVidia cards, my graphics card task usually says something like (1 NVIDIA GPU + 0.04 CPUs)
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Message 1400804 - Posted: 8 Aug 2013, 21:11:55 UTC - in response to Message 1400755.  

try running your nvidia card with a free core for a few WU cycles see if it improves(decreases) your GPU WU completion times


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Message 1400837 - Posted: 8 Aug 2013, 23:13:46 UTC - in response to Message 1400697.  


-cpu_lock -instances_per_device 2 -gpu_lock

which set the GPU jobs to run on an assigned single core. For my Phenom II, at least, that works as well as idling a core.


Did you try the same for AP and failed or just didn't try ?
AP and MB share GPU/CPU lock code so if it works for MB it should work for AP too (in theory and in latest builds)

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Message boards : Number crunching : Freeing CPU cores


 
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