Created attachment 832850 [details]
System-monitor screenshot 2

I cannot reproduce this bug.
Please take a look in the first lines of the "Event log" (open boinc manager and press SHIFT+E). You should see a line starting with "max CPUs used:". What it says?
Also, from the screenshots it seems you're running only one project (Poem) that has a multithreaded app, is that right? It seems there are 4 instances of that project running, so it seems everything ok (if you have a 4 core CPU).

I had the exact same problem running World Community Grid. Please also take a look at this thread, where there are a couple of users who experienced this bug, all using Fedora:
http://boinc.berkeley.edu/dev/forum_thread.php?id=8715

To make it clear: The log does say "Number of CPUs: 4" and 4 tasks are started, but they only use about 75% of the total CPU time, so that when a task is finished, the figures "Elapsed time" and "CPU time" differ significantly more than usual.

Number of cores = number of active BOINC tasks.


But, as you could see from my screenshots - 2 cores loaded almost 100%, but remaining 2 cores only ~50% each.
I believe - those tasks using 1 core for both.


Comparing with Fedora 17: its highly visible that Boinc crunch less tasks and CPU temperature is much lower for some cores.
CPU usage graph also shows higher load. (always 100% for all cores)
For now it is unachievable on Fedora 20.

I noticed that on my system I have high cpu usage by Ksoftirqd when I run boinc (I'm on KDE). This takes a lot of CPU, in F17 it didn't do that.

Maybe it's the same problem for you, if you're using Gnome it's maybe some other process that controls IRQs that eats a lot of CPU.

Can you please look in a console what 'top' command says? Do you see any process not boinc related that eats a lot of CPU (in my case ksoftirqd eats 7% of each core when GPU is not used and 16% of each core when using GPU apps....).

Created attachment 840027 [details]
CPU usage diagram

You could distinctly see, that most of the time 1 core is idle.

Of course some other running processes eats CPU ( 4% - 8% ). But anyway, even if this value is 25% - why BOINC doesn't load other 75% ???

Created attachment 840034 [details]
CPU with/without GPU

I don't know why, but as you can see from my screenshot I have your exact problem with GPU enabled (in the graph you can see that in the first seconds there is always a core idle and three at 100%), but as soon as I disable GPU all four cores become active at 100% and ksoftirqd does not eat CPU cicles anymore.

I'm using boinc 7.2.33 available in updates-testing. Before updating (boinc 7.0.65) ksoftirqd had high cpu usage even with GPU disabled. Please try out the updates-testing version and see if it resolve the problem (but I still think this is something due to how kernel handles CPU load/interrupts rather than a boinc problem).

I opened a bug against kernel about my problem, but seems not to be considered: #1016797

Didn't help me. 

I enabled "updates-testing" repo and installed all available updates.
Also I added to Boinc "cc_config.xml" configuration file "<no_gpus>1</no_gpus>" line.

Can you try to remove CPUShares=2 from /lib/systemd/system/boinc-client.service ?
Seems to me very low (according with systemd.exec man default is 1024) and I have removed it long time ago

Created attachment 842342 [details]
CPU usage without "CPUShares=2"

Seems that helped. Now all cores have ~ 100%  load.

Just tried if the problem does still occur with the new BOINC 7.2.33 packages - it does.
But: Removing CPUShares=2 from /lib/systemd/system/boinc-client.service (as suggested by Lorenzo Mastrogiacomi) indeed solved it for me. Thanks!

I've already applied the change in rawhide, it will be fixed in the next boinc build.

boinc-client-7.2.33-3.git1994cc8.fc20 has been submitted as an update for Fedora 20.
https://admin.fedoraproject.org/updates/boinc-client-7.2.33-3.git1994cc8.fc20

Package boinc-client-7.2.33-3.git1994cc8.fc20:
* should fix your issue,
* was pushed to the Fedora 20 testing repository,
* should be available at your local mirror within two days.
Update it with:
# su -c 'yum update --enablerepo=updates-testing boinc-client-7.2.33-3.git1994cc8.fc20'
as soon as you are able to.
Please go to the following url:
https://admin.fedoraproject.org/updates/FEDORA-2014-2160/boinc-client-7.2.33-3.git1994cc8.fc20
then log in and leave karma (feedback).

boinc-client-7.2.33-3.git1994cc8.fc20 has been pushed to the Fedora 20 stable repository.  If problems still persist, please make note of it in this bug report.