Andi Kleen wrote: >> Im running it on a x86_64 box as we speak. How can I tell if there is a >> certain mode that is permitting this? >> > > If the boot up says you're running with PMtimer then it uses the fallback > (usually happens on pre Fam10h AMD boxes). A typical Intel box > would use the faster ring 3 only TSC path and then explode with your > change I bet. > > Or step with gdb through gettimeofday() and see if it does a syscall. > > -Andi > It seems to be running fine with no indication it has fallen back. Perhaps I need a certain workload to bring out the issue? Here are some details of my system: ------------------- ghaskins@test:~> uname -a Linux test 2.6.26.3-rt3-rt #2 SMP PREEMPT RT Fri Aug 29 10:47:17 EDT 2008 x86_64 x86_64 x86_64 GNU/Linux ghaskins@test:~> cat /proc/cpuinfo processor : 0 vendor_id : GenuineIntel cpu family : 6 model : 15 model name : Intel(R) Xeon(R) CPU 5130 @ 2.00GHz stepping : 6 cpu MHz : 1995.006 cache size : 4096 KB physical id : 0 siblings : 2 core id : 0 cpu cores : 2 apicid : 0 initial apicid : 0 fpu : yes fpu_exception : yes cpuid level : 10 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 pbe syscall lm constant_tsc arch_perfmon pebs bts rep_good pni monitor ds_cpl vmx tm2 ssse3 cx16 xtpr dca lahf_lm bogomips : 3992.49 clflush size : 64 cache_alignment : 64 address sizes : 36 bits physical, 48 bits virtual power management: processor : 1 vendor_id : GenuineIntel cpu family : 6 model : 15 model name : Intel(R) Xeon(R) CPU 5130 @ 2.00GHz stepping : 6 cpu MHz : 1995.006 cache size : 4096 KB physical id : 3 siblings : 2 core id : 0 cpu cores : 2 apicid : 6 initial apicid : 6 fpu : yes fpu_exception : yes cpuid level : 10 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 pbe syscall lm constant_tsc arch_perfmon pebs bts rep_good pni monitor ds_cpl vmx tm2 ssse3 cx16 xtpr dca lahf_lm bogomips : 3990.05 clflush size : 64 cache_alignment : 64 address sizes : 36 bits physical, 48 bits virtual power management: processor : 2 vendor_id : GenuineIntel cpu family : 6 model : 15 model name : Intel(R) Xeon(R) CPU 5130 @ 2.00GHz stepping : 6 cpu MHz : 1995.006 cache size : 4096 KB physical id : 0 siblings : 2 core id : 1 cpu cores : 2 apicid : 1 initial apicid : 1 fpu : yes fpu_exception : yes cpuid level : 10 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 pbe syscall lm constant_tsc arch_perfmon pebs bts rep_good pni monitor ds_cpl vmx tm2 ssse3 cx16 xtpr dca lahf_lm bogomips : 3990.08 clflush size : 64 cache_alignment : 64 address sizes : 36 bits physical, 48 bits virtual power management: processor : 3 vendor_id : GenuineIntel cpu family : 6 model : 15 model name : Intel(R) Xeon(R) CPU 5130 @ 2.00GHz stepping : 6 cpu MHz : 1995.006 cache size : 4096 KB physical id : 3 siblings : 2 core id : 1 cpu cores : 2 apicid : 7 initial apicid : 7 fpu : yes fpu_exception : yes cpuid level : 10 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 pbe syscall lm constant_tsc arch_perfmon pebs bts rep_good pni monitor ds_cpl vmx tm2 ssse3 cx16 xtpr dca lahf_lm bogomips : 3990.04 clflush size : 64 cache_alignment : 64 address sizes : 36 bits physical, 48 bits virtual power management: ghaskins@test:~> dmesg | grep -i "pmtimer" ghaskins@test:~>
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