Message boards :
ATLAS application :
Hyperthreading/SMT
Message board moderation
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Send message Joined: 19 May 14 Posts: 10 Credit: 103,452,917 RAC: 0  
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Just wondering if there is any noticeable difference between running hyperthreading/smt on or off? Lets say a user has lots of cores/threads but limited ram. (Less than 2GB per core) Would it be worth it (points wise) to disable hyperthreading? Has anyone had any experience testing this? (I probably will...but thought I'd save some time) Thanks |
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Send message Joined: 14 Jan 10 Posts: 1274 Credit: 8,480,870 RAC: 2,011   |
I did not test with HT on/off, but with running a 4-core ATLAS VM with and without the other 4 threads idle. With half of my 8 threads idle the ATLAS job finished much faster. |
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Send message Joined: 13 May 14 Posts: 387 Credit: 15,314,184 RAC: 0 |
I posted about this a long time ago but it was probably in the old ATLAS project forums. I have a 4+4HT machine and found I got the same work done running 1 4 core WU as 1 8-core WU, i.e. the 8-core WU are twice as slow but have twice as many threads so finish in the same time. I think this is because virtualbox is not so good at exploiting HT - I have not done the same test with the native Linux version but it might work better with HT. |
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Send message Joined: 2 May 07 Posts: 2090 Credit: 158,929,705 RAC: 124,843 
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One Horse have only ONE HorsePower ;-)) T4T shows a Benchmark in the log. 2018-02-18 16:44:04 (3348): Guest Log: [INFO] Running the fast benchmark. 2018-02-18 16:45:32 (3348): Guest Log: [INFO] Machine performance 6.01 HEPSEC06 The combination of CPU, RAM, Disk(SSD) is so difficult, that there is no perfect solution for every Computer. |
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