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# ktune sysctl settings for rhel6 servers, maximizing i/o throughput
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#
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# Minimal preemption granularity for CPU-bound tasks:
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# (default: 1 msec# (1 + ilog(ncpus)), units: nanoseconds)
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kernel.sched_min_granularity_ns = 10000000
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# SCHED_OTHER wake-up granularity.
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# (default: 1 msec# (1 + ilog(ncpus)), units: nanoseconds)
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#
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# This option delays the preemption effects of decoupled workloads
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# and reduces their over-scheduling. Synchronous workloads will still
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# have immediate wakeup/sleep latencies.
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kernel.sched_wakeup_granularity_ns = 15000000
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# TODO: this bits need comment
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kernel.sched_latency_ns = 80000000
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kernel.sched_features = 15834234
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kernel.sched_tunable_scaling = 0
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# If a workload mostly uses anonymous memory and it hits this limit, the entire
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# working set is buffered for I/O, and any more write buffering would require
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# swapping, so it's time to throttle writes until I/O can catch up. Workloads
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# that mostly use file mappings may be able to use even higher values.
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#
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# The generator of dirty data starts writeback at this percentage (system default
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# is 20%)
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vm.dirty_ratio = 40
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# Start background writeback (via writeback threads) at this percentage (system
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# default is 10%)
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#vm.dirty_background_ratio = 15
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# PID allocation wrap value. When the kernel's next PID value
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# reaches this value, it wraps back to a minimum PID value.
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# PIDs of value pid_max or larger are not allocated.
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#
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# A suggested value for pid_max is 1024 * <# of cpu cores/threads in system>
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# e.g., a box with 32 cpus, the default of 32768 is reasonable, for 64 cpus,
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# 65536, for 4096 cpus, 4194304 (which is the upper limit possible).
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#kernel.pid_max = 65536
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