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    SubjectRe: [PATCH] Optimize int_sqrt for small values for faster idle
    Date
    On Mon, Feb 01 2016, Andi Kleen <ak@linux.intel.com> wrote:

    > On Mon, Feb 01, 2016 at 10:25:17PM +0100, Rasmus Villemoes wrote:
    >> On Thu, Jan 28 2016, Andi Kleen <andi@firstfloor.org> wrote:
    >>
    >> > From: Andi Kleen <ak@linux.intel.com>
    >> >
    >> > The menu cpuidle governor does at least two int_sqrt() each time
    >> > we go into idle in get_typical_interval to compute stddev
    >> >
    >> > int_sqrts take 100-120 cycles each. Short idle latency is important
    >> > for many workloads.
    >> >
    >>
    >> If you want to optimize get_typical_interval(), why not just take the
    >> square root out of the equation (literally)?
    >>
    >> Something like
    >
    > Looks good. Yes that's a better fix.
    >

    Andi, did you have a way to measure the impact, and if so, could I get
    you to run the numbers again with my patch?

    Thanks,
    Rasmus

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