MT performance lacking
Bugzilla Link | 1166 |
Created on | Oct 07, 2015 15:23 |
Version | svn |
OS | All |
Architecture | All |
Attachments | tutu.sac |
Extended Description
Created an attachment (id=1043) source code used When compiling the attached code with sac2c 1.2.beta-BlackForest-41-7dc65 (sac2c-follow branch) I find two problems: 1) sequential execution is twice as fast as mt execution with one thread 2) scaling is virtually non existant Here the exact data on a 24 core Intel Intel(R) Xeon(R) CPU X5650 @ 2.67GHz: Sequential time: -bash-4.1$ sac2c tutu3.sac -bash-4.1$ /usr/bin/time ./a.out 1.04user 0.00system 0:01.07elapsed 96%CPU (0avgtext+0avgdata 1504maxresident)k 1504inputs+0outputs (0major+422minor)pagefaults 0swaps => 1.07 sec Parallel times: -bash-4.1$ sac2c -tmt_pth tutu3.sac -bash-4.1$ /usr/bin/time ./a.out -mt 1 2.83user 0.00system 0:02.93elapsed 96%CPU (0avgtext+0avgdata 3296maxresident)k 3344inputs+0outputs (3major+363minor)pagefaults 0swaps => 2.93 secs -bash-4.1$ /usr/bin/time ./a.out -mt 2 4.92user 0.19system 0:03.37elapsed 151%CPU (0avgtext+0avgdata 4184maxresident)k 0inputs+0outputs (0major+600minor)pagefaults 0swaps => 3.37 secs -bash-4.1$ /usr/bin/time ./a.out -mt 4 4.16user 0.65system 0:01.52elapsed 316%CPU (0avgtext+0avgdata 5512maxresident)k 0inputs+0outputs (0major+510minor)pagefaults 0swaps => 1.52 secs