Questions and Answers :
Unix/Linux :
Set cpu count how ?
Message board moderation
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David Anderson (not *that* DA) Send message Joined: 5 Dec 09 Posts: 215 Credit: 74,008,558 RAC: 74 |
Just a random David A volunteer, not 'the' David A. With Hyperthreading turned on Linux reports the CPU count higher than it really is. (Xeon 5670, 2 cpus, 6 cores each shows as 24, not 12 in /proc/cpuinfo, so boinc starts too many processes for best cpu use) (This is a new machine, just going into service). This issue is known in Linux kernel discussions (google found one in 2006) but it is not really considered a bug. I'll bet there is a simple way to put some xml somewhere that will let me set the cpu count boinc projects (like Seti, Einstein) see as the cpu count. Thanks in advance for any suggestions. |
Gundolf Jahn Send message Joined: 19 Sep 00 Posts: 3184 Credit: 446,358 RAC: 0 |
Try setting "On multiprocessors, use at most 50% of the processors" in your Computing preferences (or corresponding in local preferences). Greets, Gundolf (There's no "sharp s" on a Spanish keyboard:-) |
David Anderson (not *that* DA) Send message Joined: 5 Dec 09 Posts: 215 Credit: 74,008,558 RAC: 74 |
A Dual-Core processor machine has no BIOS option letting me chose hyperthreading (Linux /proc/cpuinfo shows 'ht' in the flags, so I think the cpu has hyperthreading. Maybe.) The (new) 12 core machine BIOS has hyperthreading as an option. So I guess I either turn off hyperthreading on the 12 core machine or I live with only 1 cpu (50%) on the 2 core machine, or I just let things run as they are. I wonder which would give the best WU production (but it could take a long time to figure out... and at least with present settings all cpus are busy... so for now I'll just let things run and watch for anything odd). [Ignoring the possibility of updating BIOS/firmware on the 2-core machine...] Thanks for the prompt response. Much appreciated! |
arkayn Send message Joined: 14 May 99 Posts: 4438 Credit: 55,006,323 RAC: 0 |
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Gundolf Jahn Send message Joined: 19 Sep 00 Posts: 3184 Credit: 446,358 RAC: 0 |
So I guess I either turn off hyperthreading on the 12 core machine If you use the local preferences, only that machine is affected where you set them. Gundolf |
David Anderson (not *that* DA) Send message Joined: 5 Dec 09 Posts: 215 Credit: 74,008,558 RAC: 74 |
Ah. My goodness. The boinc-gui is perfectly clear on its preferences page that the preferences are for that computer only, but somehow the message did not penetrate my brain. Thank you Gundolf Jahn for gently pointing out I had missed the obvious. So now running 12 cores on the new machine. Interestingly having cut down the process count boinc runs from 24 to 12 resulted in the wattage decreasing by 30 watts. It is two systems on a meter (not just the one system) but the overall wattage decreased from 560 to 530 with that one change. The question arkayn raises in my head is whether I'll get more WU production with 24 processes running or with 12. Is the answer well known and certain? Or does it depend on other things? Thanks again folks. |
David Anderson (not *that* DA) Send message Joined: 5 Dec 09 Posts: 215 Credit: 74,008,558 RAC: 74 |
A forum search for 'hyperthread' turned up lots of interesting info. But no firm answer. For now I am leaving hyptherthead on but restricting to 50% so each of the 12 cores has one task. Any and all suggestions are welcome. |
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