• Len Brown's avatar
    x86, intel, power: Initialize MSR_IA32_ENERGY_PERF_BIAS · abe48b10
    Len Brown authored
    Since 2.6.36 (23016bf0), Linux prints the existence of "epb" in /proc/cpuinfo,
    Since 2.6.38 (d5532ee7), the x86_energy_perf_policy(8) utility has
    been available in-tree to update MSR_IA32_ENERGY_PERF_BIAS.
    
    However, the typical BIOS fails to initialize the MSR, presumably
    because this is handled by high-volume shrink-wrap operating systems...
    
    Linux distros, on the other hand, do not yet invoke x86_energy_perf_policy(8).
    As a result, WSM-EP, SNB, and later hardware from Intel will run in its
    default hardware power-on state (performance), which assumes that users
    care for performance at all costs and not for energy efficiency.
    While that is fine for performance benchmarks, the hardware's intended default
    operating point is "normal" mode...
    
    Initialize the MSR to the "normal" by default during kernel boot.
    
    x86_energy_perf_policy(8) is available to change the default after boot,
    should the user have a different preference.
    Signed-off-by: default avatarLen Brown <len.brown@intel.com>
    Link: http://lkml.kernel.org/r/alpine.LFD.2.02.1107140051020.18606@x980Acked-by: default avatarRafael J. Wysocki <rjw@sisk.pl>
    Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
    Cc: <stable@kernel.org>
    abe48b10
msr-index.h 15.9 KB