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Four-core tasks only using one core

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Donald Qualls

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Message 60535 - Posted: 7 Dec 2013, 16:29:53 UTC

I've recently noticed my average credit dropping, and a quick check showed my CPU monitor had only a single core running at 100%; the other three were running almost nothing on "nice" priority (in which MilkyWay is the only task). The task list in BOINC manager shows a task running on 4.0 CPU, preventing other tasks from running while it's "up front" -- yet that task, with name starting "ps_nbody_12_5_sim_orphan" is showing in my System Activity as using only 25% of my total CPU resources, i.e. one core out of four. It's also not yet showing an estimated completion time, despite the fact it's been running for two and a half hours (it also shows 0% completed at this time). I've just had one task in this class finish, I've another pre-fetched -- I'm thinking these tasks are malfunctioning in some fashion and preventing the ones that are working right from getting CPU time.

For whatever it's worth, I'm running BOINC manager 6.10.58 (latest version available in my repositories) and what I presume to be current Milky Way modules, on a Core Quad 8400, 4 cores at 2.67 GHz, 4 GiB RAM, plenty of clear HDD space, under MEPIS 11 64-bit (Debian stable based) Linux; this system is also running Einstein@home on GPU only (can't run MilkyWay on GPU; my nVidia GT520 GPU lacks double precision floating point capability).

Anyone else seen this, have a suggestion, etc.?
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Message 60539 - Posted: 8 Dec 2013, 12:00:14 UTC - in response to Message 60535.  

I've recently noticed my average credit dropping, and a quick check showed my CPU monitor had only a single core running at 100%; the other three were running almost nothing on "nice" priority (in which MilkyWay is the only task). The task list in BOINC manager shows a task running on 4.0 CPU, preventing other tasks from running while it's "up front" -- yet that task, with name starting "ps_nbody_12_5_sim_orphan" is showing in my System Activity as using only 25% of my total CPU resources, i.e. one core out of four. It's also not yet showing an estimated completion time, despite the fact it's been running for two and a half hours (it also shows 0% completed at this time). I've just had one task in this class finish, I've another pre-fetched -- I'm thinking these tasks are malfunctioning in some fashion and preventing the ones that are working right from getting CPU time.

For whatever it's worth, I'm running BOINC manager 6.10.58 (latest version available in my repositories) and what I presume to be current Milky Way modules, on a Core Quad 8400, 4 cores at 2.67 GHz, 4 GiB RAM, plenty of clear HDD space, under MEPIS 11 64-bit (Debian stable based) Linux; this system is also running Einstein@home on GPU only (can't run MilkyWay on GPU; my nVidia GT520 GPU lacks double precision floating point capability).

Anyone else seen this, have a suggestion, etc.?


Some MilkyWay cpu tasks are what are called MT tasks, or multi-threaded tasks, this means one unit will use all available cpu cores, sort of like a super computer does when it does things. They are phasing them out so over time you should see less and less of these. They don't usually last very long, mine were lasting in the 5 minute range using 5 of the 6 cores on my cpu.
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Donald Qualls

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Message 60541 - Posted: 8 Dec 2013, 16:32:46 UTC - in response to Message 60539.  

Some MilkyWay cpu tasks are what are called MT tasks, or multi-threaded tasks, this means one unit will use all available cpu cores, sort of like a super computer does when it does things. They are phasing them out so over time you should see less and less of these. They don't usually last very long, mine were lasting in the 5 minute range using 5 of the 6 cores on my cpu.


I'm familiar with the multi-thread tasks; as you note, on a reasonably fast multi-core CPU they don't bog things down, and keep my CPU usage at 100% for all four cores. What I have here, though, is a task that's demanding all four cores (and blocking other tasks from using them), but only using one. Further, the current one has been running for 19+ hours at this point, and still shows 0% complete. There are two more of these tasks in my queue, as well.

So far they're dropped my average credit by 25% over the past week, indicating very inefficient resource use. I believe this is a bug in these tasks or their computation module; if they're intended to use multiple cores, they're failing to do so, and if they're not, they shouldn't be monopolizing the CPU.
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Message 60545 - Posted: 10 Dec 2013, 12:51:02 UTC - in response to Message 60541.  

Some MilkyWay cpu tasks are what are called MT tasks, or multi-threaded tasks, this means one unit will use all available cpu cores, sort of like a super computer does when it does things. They are phasing them out so over time you should see less and less of these. They don't usually last very long, mine were lasting in the 5 minute range using 5 of the 6 cores on my cpu.


I'm familiar with the multi-thread tasks; as you note, on a reasonably fast multi-core CPU they don't bog things down, and keep my CPU usage at 100% for all four cores. What I have here, though, is a task that's demanding all four cores (and blocking other tasks from using them), but only using one. Further, the current one has been running for 19+ hours at this point, and still shows 0% complete. There are two more of these tasks in my queue, as well.

So far they're dropped my average credit by 25% over the past week, indicating very inefficient resource use. I believe this is a bug in these tasks or their computation module; if they're intended to use multiple cores, they're failing to do so, and if they're not, they shouldn't be monopolizing the CPU.


I personally would just abort the current one of them and move on, 19 hours is way too long to still be at zero percent!! AND if the next one starts out the same way I would abort it too!!
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Message 60551 - Posted: 11 Dec 2013, 8:57:11 UTC - in response to Message 60535.  

Hi Donald

For a start I would not use the version of BOINC that comes in your repository as they can be significantly out of date. (I am using Ubuntu Linux 13.10 here.). The current versions of BOINC are 7.xx series.

The best way to do it is to create a boinc directroy in your HOME directory. Download/install boinc using the latest boinc and install instructions from the boinc site. Then add your project(s) as per normal. You will then get the latest apps to get around the issue you are having, potentually incluting optimised apps to further improve your results.

Hope this helps


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Donald Qualls

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Message 60592 - Posted: 15 Dec 2013, 4:16:58 UTC - in response to Message 60551.  

I personally would just abort the current one of them and move on, 19 hours is way too long to still be at zero percent!! AND if the next one starts out the same way I would abort it too!!


I did; others of that same series seem fine, so I presume it was something specific to that one or two tasks.

Hi Donald

For a start I would not use the version of BOINC that comes in your repository as they can be significantly out of date. (I am using Ubuntu Linux 13.10 here.). The current versions of BOINC are 7.xx series.

The best way to do it is to create a boinc directroy in your HOME directory. Download/install boinc using the latest boinc and install instructions from the boinc site. Then add your project(s) as per normal. You will then get the latest apps to get around the issue you are having, potentually incluting optimised apps to further improve your results.

Hope this helps




I've never managed to install BOINC from the download, and the download page tells me to use the one in my repository if it's available. I agree, for software that undergoes significant ongoing development, the repo version is often seriously dated -- but the current download needs to be capable of installation by those who'll use it. I need a .deb package (I'm using a Debian based distro) or a tarball; I'm not yet knowledgeable enough in Linux to compile my own apps from source.
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