* Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > 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. In terms of build and documentation environment, tools/perf/ has one cloned/inherited from Git, which is rather good and functional. Sharing it with the kernel's build system depends on the kbuild developers being interested in it. Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
