Hi, I just have tried two other setups on the x86_64 machine: 1. Ubuntu Feisty Fawn (gcc 4.1.2) server x86: - Expected performance: about two times faster than on my notebook 2. Ubuntu Gutsy Gibbon (gcc 4.2.1) server x86: - nearly same performance than "Ubuntu Feisty Fawn (gcc 4.1.2) server x86" - Expected performance: about two times faster than on my notebook Was there a change from gcc 4.1.2 to gcc 4.2.1 which could explain that? Or is there anything else which could explain that? Ralf On Wednesday, 26. September 2007 10:35:20 Ralf Lübben wrote: > Hello, > > in the last days I ran a simulation on a x86_64 architecture: > ################### > processor : 0 > vendor_id : GenuineIntel > cpu family : 15 > model : 6 > model name : Genuine Intel(R) CPU 3.20GHz > stepping : 8 > cpu MHz : 3192.081 > cache size : 8192 KB > physical id : 0 > siblings : 2 > core id : 0 > cpu cores : 2 > fpu : yes > fpu_exception : yes > cpuid level : 6 > wp : yes > flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca > cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall nx lm > constant_tsc pni monitor ds_cpl vmx est tm2 cid cx16 xtpr lahf_lm > bogomips : 6390.34 > clflush size : 64 > cache_alignment : 128 > address sizes : 40 bits physical, 48 bits virtual > power management: > ##################### > > with very poor performance. > > I ran the same simulations on my notebook: > > ###################### > processor : 0 > vendor_id : AuthenticAMD > cpu family : 6 > model : 8 > model name : mobile AMD Athlon(tm) XP 2000+ > stepping : 1 > cpu MHz : 797.820 > cache size : 256 KB > fdiv_bug : no > hlt_bug : no > f00f_bug : no > coma_bug : no > fpu : yes > fpu_exception : yes > cpuid level : 1 > wp : yes > flags : fpu vme de pse tsc msr pae mce cx8 sep mtrr pge mca cmov > pat pse36 mmx fxsr sse syscall mp mmxext 3dnowext 3dnow ts fid vid > bogomips : 1596.37 > clflush size : 32 > ####################### > > The same simulation is about 10 times faster on my notebook. > The simulation was compiled with "-O3 -ffast-math", without "-ffast-math" > the performance of the x86_64 architecture is much worse. > I used gcc 4.1.2 on Ubuntu, the simulator is Omnet++. > > There was already a post about the topic: > http://gcc.gnu.org/ml/gcc-help/2006-05/msg00185.html > on AMD machines. > > I could also figure out, that one problem ist the pow() function, maybe > there are more functions with poor performance on x86_64 machines. > > Has anyone an idea about the reasons or how to improve the performance on > x86_64 machines? > > Thanks. > > Regards, > Ralf
