top command doesn't display all processors running
Dear List, I am writting OpenMP parallel programs which use all the processors of my Quad Opteron baby! Now, suppose that all the 4 processors are running the same application. Typing #top I would expect to see 4 processes with 99.9% CPU usage. Instead of that I see only one! That is in my SuSE 9.2 AMD64. The same thing in SuSE 9.0 with icc compiler and OpenMP displays in top all the OMP_NUM_THREADS exported in bash by #export OMP_NUM_THREADS=4 even in a uni-processor pentium4. What is wrong with top in SuSE 9.2 and how can I fix it? Thanks in advance! Simeon! __________________________________ Do you Yahoo!? Yahoo! Small Business - Try our new resources site! http://smallbusiness.yahoo.com/resources/
Simeon Nifos wrote:
I would expect to see 4 processes with 99.9% CPU usage. Instead of that I see only one! That is in my SuSE 9.2 AMD64.
I believe this is related to the linux kernel, the new threading architecture (NPTL), and how stats are gathered & reported in /proc. I don't think its a x86_64 (or suse) specific problem. I found most of this out by googling a while back so dont take this as a definative answer. I also read they are addressing some of these issues with the newer kernels but I dont know to what degree. Mark
Mark Horton wrote:
Simeon Nifos wrote:
I would expect to see 4 processes with 99.9% CPU usage. Instead of that I see only one! That is in my SuSE 9.2 AMD64.
I believe this is related to the linux kernel, the new threading architecture (NPTL), and how stats are gathered & reported in /proc. I don't think its a x86_64 (or suse) specific problem.
I found most of this out by googling a while back so dont take this as a definative answer. I also read they are addressing some of these issues with the newer kernels but I dont know to what degree.
I think I misunderstood your original question. The issue I was having was that top would not display a multi-threaded process at all, and I thought this might be related to your prblem. On my system top shows that the cpu is busy but it does not show which process is using the CPU. I compiled and installed the latest stable vanilla kernel (2.6.11.5) and top now shows which process is actually using the CPU. Mark
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Mark Horton -
Simeon Nifos