About use of kernel parameter 'sched'

Resolution

• kernel.sched_child_runs_first
  This parameter controls whether process scheduled next after fork is
  the parent or child. If set to 0, the parent is scheduled next.

• kernel.sched_latency_ns
  sched_latency_ns is the initial value for the scheduler
  period. The scheduler period is a period of time during which all
  runnable tasks should be allowed to run at least once. While CFS has
  no concept of time slices, you can think of the period as the
  initial chunk of time which is then divided evenly into timeslices,
  one for each runnable process. Note that this tunable only specifies
  the initial value. When too many tasks become runnable the scheduler
  will use kernel.sched_min_granularity_ns instead .
  /usr/share/doc/kernel-doc-2.6.32/Documentation/scheduler/sched-design-CFS.txt

• kernel.sched_min_granularity_ns
  sched_min_granularity_ns specifies the target minimum scheduler period in which a single task will run. This tunable is used only when running load is high. Unlike sched_latency_ns, this tunable specifies the target period allocated for each task to run rather than the time in which all tasks should be run once.

• kernel.sched_wakeup_granularity_ns
  It gives preemption granularity when tasks wake up.

• kernel.sched_shares_ratelimit
  This parameter is used for updating the group shares.
  However, it was obsolete in RHEL6.2 due to a patch from
  upstream. For the detail please see the following.
  http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=2069dd75c7d0f49355939e5586daf5a9ab216db7

• kernel.sched_tunable_scaling
  sched_tunable_scaling controls whether the scheduler can adjust
  sched_latency_ns. The values are 0 = do not adjust, 1 = logarithmic
  adjustment, and 2 = linear adjustment.
  The adjustment made is based on the number of CPUs, and increases
  logarithmically or linearly as implied in the available values. This
  is due to the fact that with more CPUs there's an apparent reduction
  in perceived latency.

• kernel.sched_migration_cost
  Amount of time after the last execution that a task is considered to
  be “cache hot” in migration decisions. A “hot” task is less
  likely to be migrated, so increasing this variable reduces task
  migrations. The default value is 500000 (ns).
  If the CPU idle time is higher than expected when there are runnable
  processes, try reducing this value. If tasks bounce between CPUs or
  nodes too often, try increasing it.

• kernel.sched_nr_migrate
  If a SCHED_OTHER task spawns a large number of other tasks, they
  will all run on the same CPU. The migration task or softirq will try
  to balance these tasks so they can run on idle CPUs. The
  sched_nr_migrate option can be set to specify the number of tasks
  that will move at a time.

• kernel.sched_shares_thresh
  It works to inject some fuzzyness into changing the per-cpu group
  shares. This avoids remote rq-locks at the expense of fairness.
  However, it was obsolete in RHEL6.2 as well as
  sched_shares_ratelimit. Please refer to the above upstream
  information.

• kernel.sched_features
  This parameter allows you to enable or disable scheduler features for debugging purposes.

  NO_GENTLE_FAIR_SLEEPERS = 1
  NO_START_DEBIT = 2
  NO_WAKEUP_PREEMPT = 4
  NO_AFFINE_WAKEUPS = 8
  NEXT_BUDDY = 16
  NO_LAST_BUDDY = 32
  NO_CACHE_HOT_BUDDY = 64
  ARCH_POWER = 128
  HRTICK = 256
  DOUBLE_TICK = 512
  NO_LB_BIAS = 1024
  NO_OWNER_SPIN = 2048

• kernel.sched_time_avg
  sched_time_avg is a period of time over which the average real-time
  task CPU consumption is averaged. The resulting average is used to
  adjust CPU power for non-real-time tasks to ensure that real-time
  tasks don't have to fight for CPU time.