Hakan BAYINDIR wrote: > Volkan YAZICI wrote: >> On Tue, 01 Jul 2008, Hakan BAYINDIR <[EMAIL PROTECTED]> writes: >>> # >>> # CPU Frequency scaling >>> # >>> CONFIG_CPU_FREQ=y >>> CONFIG_CPU_FREQ_TABLE=m >>> # CONFIG_CPU_FREQ_DEBUG is not set >>> CONFIG_CPU_FREQ_STAT=m >>> # CONFIG_CPU_FREQ_STAT_DETAILS is not set >>> CONFIG_CPU_FREQ_DEFAULT_GOV_PERFORMANCE=y >>> # CONFIG_CPU_FREQ_DEFAULT_GOV_USERSPACE is not set >>> # CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND is not set >>> # CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE is not set >>> CONFIG_CPU_FREQ_GOV_PERFORMANCE=y >>> CONFIG_CPU_FREQ_GOV_POWERSAVE=m >>> CONFIG_CPU_FREQ_GOV_USERSPACE=m >>> CONFIG_CPU_FREQ_GOV_ONDEMAND=m >>> CONFIG_CPU_FREQ_GOV_CONSERVATIVE=m >>> >>> # >>> # CPUFreq processor drivers >>> # >>> CONFIG_X86_ACPI_CPUFREQ=m >>> CONFIG_X86_POWERNOW_K6=m >>> CONFIG_X86_POWERNOW_K7=m >>> CONFIG_X86_POWERNOW_K7_ACPI=y >>> CONFIG_X86_POWERNOW_K8=m >>> CONFIG_X86_POWERNOW_K8_ACPI=y >>> CONFIG_X86_GX_SUSPMOD=m >>> CONFIG_X86_SPEEDSTEP_CENTRINO=m >>> CONFIG_X86_SPEEDSTEP_CENTRINO_TABLE=y >>> CONFIG_X86_SPEEDSTEP_ICH=m >>> CONFIG_X86_SPEEDSTEP_SMI=m >>> CONFIG_X86_P4_CLOCKMOD=m >>> CONFIG_X86_CPUFREQ_NFORCE2=m >>> CONFIG_X86_LONGRUN=m >>> CONFIG_X86_LONGHAUL=m >>> CONFIG_X86_E_POWERSAVER=m >> Also "lsmod" output will be helpful as well. >> >> >> Regards. >> >> > > After subscribing to cpu-freq mailing list and asking the same question here, > Venkatesh Pallipadi from intel answered my question. He said that since > voltages > in a CPU package is constant across cores, keeping frequencies low on other > cores while clocking one up doesn't save considerable amount of power. Because > of this fact, they keep the frequencies in a core synchronized if possible. > > Since his message is more informational than that, I'm quoting information > parts > from the conversation below: > >> In actual hardware, voltage is coordinated at socket level and that is the >> reason frequencies in one socket are tied together. Now, what has changed in >> two above config will be the mode in which kernel operates: >> 1) Hardware coordination mode: Kernel thinks each core is having independent >> frequency and reports the same. Underneath, hardware does frequency >> coodination and picks the highest requested frequency among all cores and >> runs all cores at that freq. >> 2) Software coordination mode: Kernel understands which specific CPUs are >> dependent and picks the highest frequency needed among all such dependent >> cores and makes single request for such frequency and reports the same. >> >> Note that there should not be any power consumption difference with these >> two kernels on under identical load. Just that the kernel now knows more >> about the frequency dependencies in the platform. > > and > >> Both Core 2 Duo and Core 2 Quad, voltage is sync'ed across all cores in a >> single socket due to VR restriction. Most of the power savings from lower >> freq comes from lower voltage. As all cores in a single socket runs on same >> voltage here, independent voltage is not possible. On a real multi-socket >> system (dual or quad socket serves, cores in each socket can be at different >> frequencies though). >> >> Older linux kernel only supports hardware coordination which explains the >> pre 2.6.21 behavior. Newer Linux kernel picks up hardware coordination mode >> or software coordination mode based on depending on BIOS capability and >> information it gets from BIOS ACPI table. So, it is possible that different >> systems have different coordination mode active, with same kernel. > > > Thanks to all for your help and time, > > Cheers and Regards, > > --Hakan > > P.S: > > For reference, my PC configuration is below: > > CPU: Intel Core2Quad Q6600, 2.4GHz > M/B: MSI P35 Platinum, BIOS ver. 1.8 > RAM: 4GB OCz Flex XLC CL3 DDR2 > Distro: Debian testing > Kernel: 2.6.24-1-686-bigmem >
Umm a last, small clarification: It seems like Core series CPUs cannot scale their cores independently and this was an illusion I saw from kernel behavior. After reading the conversation again, I got it completely. Thanks again. Cheers, --Hakan.
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