shino korah wrote: > Hi, .... snip.... > This results shows HT improves performance if we have > 4 tasks on DP system and performance is hit if we use > 2 tasks on a DP system. > > I did use kernel 2.4.9 did you repeat the tests several times? as i remember from ingo's article, he found HT with the non-HT-aware scheduler (but on 2.5, using O(1)) gave a big variations between the best and worst time. apparently it was randomly assingning the processes to the virtual cpus without regard of the real cpu utilization. his HT-aware scheduler didn't get a better performance, but stayed solidly at the best time he got with the old scheduler > I wrote this to make sure my assumptions are correct > and I'm getting performance as expected.Correct me if > I'm wrong. i think your 2 process case was degraded becaouse sometimes one (real) processor had to do all the work and the scheduler didn't noticed the inbalance; but having 4 processes made it fill every virtual cpu, achieving real balance just by the coincidence of the numbers on the real world you usually don't have as much control on the number of processes, and very seldom you can start 4 computation-intensive processes and finish all at roughly the same time the HT-aware scheduler would keep the real cpus balanced most of the time, but in 2.4.9 you would have to depend on chance also, i don't know if the 2.4 scheduler implements any cpu-affinity heuristics; these usually help by reducing cache trashing; but would perpetuate a cpu inbalance caused by the HT-ignorance of the scheduler ------ Javier -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
