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    SubjectRe: [PATCH] tools: add x86_energy_perf_policy to program MSR_IA32_ENERGY_PERF_BIAS

    * Andrew Morton <akpm@linux-foundation.org> wrote:

    > On Sat, 23 Oct 2010 00:40:18 -0400 (EDT) Len Brown <lenb@kernel.org> 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@intel.com>
    > > ---
    > > 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


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