On Sat, 23 Oct 2010 00:40:18 -0400 (EDT) Len Brown <lenb@xxxxxxxxxx> wrote: > MSR_IA32_ENERGY_PERF_BIAS first became available on Westmere Xeon. > It is implemented in all Sandy Bridge processors -- mobile, desktop and server. > It is expected to become increasingly important in subsequent generations. > > x86_energy_perf_policy is a user-space utility to set this > hardware energy vs performance policy hint in the processor. > Most systems would benefit from "x86_energy_perf_policy normal" > at system startup, as the hardware default is maximum performance > at the expense of energy efficiency. See the comments > in the source code for more information. > > Linux-2.6.36 added "epb" to /proc/cpuinfo to indicate > if an x86 processor supports MSR_IA32_ENERGY_PERF_BIAS, > though the kernel does not actually program the MSR. > > In March, Venkatesh Pallipadi proposed a small driver > that programmed MSR_IA32_ENERGY_PERF_BIAS, based on > the cpufreq governor in use. It also offered > a boot-time cmdline option to override. > http://lkml.org/lkml/2010/3/4/457 > But hiding the hardware policy behind the > governor choice was deemed "kinda icky". > > So in June, I proposed a generic user/kernel API to > consolidate the power/performance policy trade-off. > "RFC: /sys/power/policy_preference" > http://lkml.org/lkml/2010/6/16/399 > That is my preference for implementing this capability, > but I received no support on the list. > > So in September, I sent x86_energy_perf_policy.c to LKML, > a user-space utility that scribbles directly to the MSR. > http://lkml.org/lkml/2010/9/28/246 > > Here is the same utility re-sent, this time proposed > to reside in the kernel tools directory. > > Signed-off-by: Len Brown <len.brown@xxxxxxxxx> > --- > tools/power/x86/x86_energy_perf_policy/Makefile | 7 + > .../x86_energy_perf_policy.c | 358 ++++++++++++++++++++ > 2 files changed, 365 insertions(+), 0 deletions(-) > create mode 100644 tools/power/x86/x86_energy_perf_policy/Makefile > create mode 100644 tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.c tools/power/x86, eh? It seems a better place than under Documentation/, where such things have thus far landed! I looked briefly, wondering about the kbuild situation. It doesn't appear to be wired up, so one has to manually enter that directory and type `make'? I guess that's OK as an interim thing but longer-term I suppose we should have some more complete build and deployment system. So (thinking out loud) a `make' would invoke a `make tools', and that `make tools' would build the tools which are specific to the target arch[*], and any generic ones. And a `make tools_install' would install those tools in, I guess, /lib/modules/$(uname -r)/bin. Or something else. We'd need input from the distro guys to get this right. [*]: building tools for the `target arch' would require a far more extensive cross-build environment than is needed for just kernel cross-compilation. This is perhaps Just Too Hard and perhaps a `make tools_install' should copy the *source* into /lib/modules/$(uname -r)/src and you then finish the build on the target. Or something else. The mind boggles. So for now, just parking the source down in ./tools/ and deferring the problem sounds a fine idea ;) A number of programs down under Documentation/ should be moved into tools/ as well. _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
