https://community.hpe.com/t5/proliant-servers-ml-dl-sl/inconsistent-performance-with-dl785-using-mpi/m-p/4653778#M103760 We are using a DL785 G6 system with 8x Opteron 6-core processors (48core) with 256 GB total memory. We are running a computationally and memory intensive model, which uses MPI, testing the scalability of said model. System OS is RH Enterprise Linux 5.5.<BR /><BR />Running on (for example) 12 cores produces inconsistent performance results - run times vary greatly depending on which processors get assigned to the tasks. Running on increasing numbers of cores yields diminishing returns.<BR /><BR />Running a single threaded test, 47 instances of a calculation of PI to 100,000,000 digits produced strange results as well. Performance for each instance was consistent (seconds per digit calculated) while all 47 threads were running - however, 28 threads performed at speed X, while the remaining 19 cores performed at 75% to 50% of the speed of the fastest cores. Memory availability was not an issue for this test (memory footprint of the program was small). After some threads terminated, a visible improvement occurred in the remaining threads - whether they actually migrated processors or just improved performance is unknown.<BR /><BR />Does anyone know why the same program running on each core would perform significantly slower on some cores when all processors are identical?<BR /> Mon, 28 Jun 2010 14:12:40 GMT David B Hart 2010-06-28T14:12:40Z https://community.hpe.com/t5/proliant-servers-ml-dl-sl/inconsistent-performance-with-dl785-using-mpi/m-p/4653778#M103760 We are using a DL785 G6 system with 8x Opteron 6-core processors (48core) with 256 GB total memory. We are running a computationally and memory intensive model, which uses MPI, testing the scalability of said model. System OS is RH Enterprise Linux 5.5.<BR /><BR />Running on (for example) 12 cores produces inconsistent performance results - run times vary greatly depending on which processors get assigned to the tasks. Running on increasing numbers of cores yields diminishing returns.<BR /><BR />Running a single threaded test, 47 instances of a calculation of PI to 100,000,000 digits produced strange results as well. Performance for each instance was consistent (seconds per digit calculated) while all 47 threads were running - however, 28 threads performed at speed X, while the remaining 19 cores performed at 75% to 50% of the speed of the fastest cores. Memory availability was not an issue for this test (memory footprint of the program was small). After some threads terminated, a visible improvement occurred in the remaining threads - whether they actually migrated processors or just improved performance is unknown.<BR /><BR />Does anyone know why the same program running on each core would perform significantly slower on some cores when all processors are identical?<BR /> Mon, 28 Jun 2010 14:12:40 GMT https://community.hpe.com/t5/proliant-servers-ml-dl-sl/inconsistent-performance-with-dl785-using-mpi/m-p/4653778#M103760 David B Hart 2010-06-28T14:12:40Z https://community.hpe.com/t5/proliant-servers-ml-dl-sl/inconsistent-performance-with-dl785-using-mpi/m-p/4653779#M103761 Hello David,<BR />we use DL785G5 (32cores, 128GB ram) as MS SQL data warehouse.<BR />Server performance is great, but we do different kind of task than you.<BR /><BR />Jan Tue, 29 Jun 2010 18:13:41 GMT https://community.hpe.com/t5/proliant-servers-ml-dl-sl/inconsistent-performance-with-dl785-using-mpi/m-p/4653779#M103761 Jan Soska 2010-06-29T18:13:41Z