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    SubjectRe: [RFC PATCH v4] sched/fair: select idle cpu from idle cpumask for task wakeup
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    On 2020/11/18 20:06, Valentin Schneider wrote:
    >
    > On 16/11/20 20:04, Aubrey Li wrote:
    >> From: Aubrey Li <aubrey.li@intel.com>
    >>
    >> Add idle cpumask to track idle cpus in sched domain. When a CPU
    >> enters idle, if the idle driver indicates to stop tick, this CPU
    >> is set in the idle cpumask to be a wakeup target. And if the CPU
    >> is not in idle, the CPU is cleared in idle cpumask during scheduler
    >> tick to ratelimit idle cpumask update.
    >>
    >> When a task wakes up to select an idle cpu, scanning idle cpumask
    >> has low cost than scanning all the cpus in last level cache domain,
    >> especially when the system is heavily loaded.
    >>
    >> Benchmarks were tested on a x86 4 socket system with 24 cores per
    >> socket and 2 hyperthreads per core, total 192 CPUs. Hackbench and
    >> schbench have no notable change, uperf has:
    >>
    >> uperf throughput: netperf workload, tcp_nodelay, r/w size = 90
    >>
    >> threads baseline-avg %std patch-avg %std
    >> 96 1 0.83 1.23 3.27
    >> 144 1 1.03 1.67 2.67
    >> 192 1 0.69 1.81 3.59
    >> 240 1 2.84 1.51 2.67
    >>
    >> Cc: Mel Gorman <mgorman@suse.de>
    >> Cc: Vincent Guittot <vincent.guittot@linaro.org>
    >> Cc: Qais Yousef <qais.yousef@arm.com>
    >> Cc: Valentin Schneider <valentin.schneider@arm.com>
    >> Cc: Jiang Biao <benbjiang@gmail.com>
    >> Cc: Tim Chen <tim.c.chen@linux.intel.com>
    >> Signed-off-by: Aubrey Li <aubrey.li@linux.intel.com>
    >
    > That's missing a v3 -> v4 change summary
    >

    okay, I'll add in the next version soon.

    Thanks,
    -Aubrey

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