Peter Ziljstra noticed that the sleeper bonus deduction code
was not properly rate-limited: a task that scheduled more
frequently would get a disproportionately large deduction.
So limit the deduction to delta_exec.
Signed-off-by: NIngo Molnar <mingo@elte.hu>

while there's no in-tree way to turn group scheduling at the moment,
fix a typo in it nevertheless.
Signed-off-by: NIngo Molnar <mingo@elte.hu>

refine the granularity of negative nice level tasks: let them
reschedule more often to offset the effect of them consuming
their wait_runtime proportionately slower. (This makes nice-0
task scheduling smoother in the presence of negatively
reniced tasks.)
Signed-off-by: NIngo Molnar <mingo@elte.hu>

the key has to be rescaled to /weight even if it has a positive value.

(this change only affects the scheduling of reniced tasks)
Signed-off-by: NIngo Molnar <mingo@elte.hu>

clean up set_curr_task_fair().

( identity transformation that causes no change in functionality. )

   text    data     bss     dec     hex filename
  39170    3750      36   42956    a7cc sched.o.before
  39170    3750      36   42956    a7cc sched.o.after
Signed-off-by: NIngo Molnar <mingo@elte.hu>

remove __update_rq_clock() call from entity_tick().

no change in functionality because scheduler_tick() already calls
__update_rq_clock().
Signed-off-by: NIngo Molnar <mingo@elte.hu>

final step: remove all (now superfluous) 'u64 now' variables.

( identity transformation that causes no change in functionality. )
Signed-off-by: NIngo Molnar <mingo@elte.hu>

remove the 'u64 now' parameter from ->task_new().

( identity transformation that causes no change in functionality. )
Signed-off-by: NIngo Molnar <mingo@elte.hu>

remove the 'u64 now' parameter from ->put_prev_task().

( identity transformation that causes no change in functionality. )
Signed-off-by: NIngo Molnar <mingo@elte.hu>

remove the 'u64 now' parameter from ->pick_next_task().

( identity transformation that causes no change in functionality. )
Signed-off-by: NIngo Molnar <mingo@elte.hu>

remove the 'u64 now' parameter from ->dequeue_task().

( identity transformation that causes no change in functionality. )
Signed-off-by: NIngo Molnar <mingo@elte.hu>

remove the 'u64 now' parameter from ->enqueue_task().

( identity transformation that causes no change in functionality. )
Signed-off-by: NIngo Molnar <mingo@elte.hu>

remove the 'u64 now' parameter from put_prev_entity().

( identity transformation that causes no change in functionality. )
Signed-off-by: NIngo Molnar <mingo@elte.hu>

remove the 'u64 now' parameter from pick_next_entity().

( identity transformation that causes no change in functionality. )
Signed-off-by: NIngo Molnar <mingo@elte.hu>

remove the 'u64 now' parameter from set_next_entity().

( identity transformation that causes no change in functionality. )
Signed-off-by: NIngo Molnar <mingo@elte.hu>

remove the 'u64 now' parameter from dequeue_entity().

( identity transformation that causes no change in functionality. )
Signed-off-by: NIngo Molnar <mingo@elte.hu>

remove the 'u64 now' parameter from enqueue_entity().

( identity transformation that causes no change in functionality. )
Signed-off-by: NIngo Molnar <mingo@elte.hu>

remove the 'u64 now' parameter from enqueue_sleeper().

( identity transformation that causes no change in functionality. )
Signed-off-by: NIngo Molnar <mingo@elte.hu>

remove the 'u64 now' parameter from __enqueue_sleeper().

( identity transformation that causes no change in functionality. )
Signed-off-by: NIngo Molnar <mingo@elte.hu>

remove the 'u64 now' parameter from update_stats_curr_end().

( identity transformation that causes no change in functionality. )
Signed-off-by: NIngo Molnar <mingo@elte.hu>

remove the 'u64 now' parameter from update_stats_dequeue().

( identity transformation that causes no change in functionality. )
Signed-off-by: NIngo Molnar <mingo@elte.hu>

remove the 'u64 now' parameter from update_stats_curr_start().

( identity transformation that causes no change in functionality. )
Signed-off-by: NIngo Molnar <mingo@elte.hu>

remove the 'u64 now' parameter from update_stats_wait_end().

( identity transformation that causes no change in functionality. )
Signed-off-by: NIngo Molnar <mingo@elte.hu>

remove the 'u64 now' parameter from __update_stats_wait_end().

( identity transformation that causes no change in functionality. )
Signed-off-by: NIngo Molnar <mingo@elte.hu>

remove the 'u64 now' parameter from update_stats_enqueue().

( identity transformation that causes no change in functionality. )
Signed-off-by: NIngo Molnar <mingo@elte.hu>

remove the 'u64 now' parameter from update_stats_wait_start().

( identity transformation that causes no change in functionality. )
Signed-off-by: NIngo Molnar <mingo@elte.hu>

remove the 'u64 now' parameter from update_curr().

( identity transformation that causes no change in functionality. )
Signed-off-by: NIngo Molnar <mingo@elte.hu>

remove the 'u64 now' parameter from print_cfs_rq().

( identity transformation that causes no change in functionality. )
Signed-off-by: NIngo Molnar <mingo@elte.hu>

change all 'now' timestamp uses in assignments to rq->clock.

( this is an identity transformation that causes no functionality change:
  all such new rq->clock is necessarily preceded by an update_rq_clock()
  call. )
Signed-off-by: NIngo Molnar <mingo@elte.hu>

eliminate __rq_clock() use by changing it to:

   __update_rq_clock(rq)
   now = rq->clock;

identity transformation - no change in behavior.
Signed-off-by: NIngo Molnar <mingo@elte.hu>

eliminate rq_clock() use by changing it to:

   update_rq_clock(rq)
   now = rq->clock;

identity transformation - no change in behavior.
Signed-off-by: NIngo Molnar <mingo@elte.hu>

There are two problems with balance_tasks() and how it used:

1. The variables best_prio and best_prio_seen (inherited from the old
move_tasks()) were only required to handle problems caused by the
active/expired arrays, the order in which they were processed and the
possibility that the task with the highest priority could be on either.
  These issues are no longer present and the extra overhead associated
with their use is unnecessary (and possibly wrong).

2. In the absence of CONFIG_FAIR_GROUP_SCHED being set, the same
this_best_prio variable needs to be used by all scheduling classes or
there is a risk of moving too much load.  E.g. if the highest priority
task on this at the beginning is a fairly low priority task and the rt
class migrates a task (during its turn) then that moved task becomes the
new highest priority task on this_rq but when the sched_fair class
initializes its copy of this_best_prio it will get the priority of the
original highest priority task as, due to the run queue locks being
held, the reschedule triggered by pull_task() will not have taken place.
  This could result in inappropriate overriding of skip_for_load and
excessive load being moved.

The attached patch addresses these problems by deleting all reference to
best_prio and best_prio_seen and making this_best_prio a reference
parameter to the various functions involved.

load_balance_fair() has also been modified so that this_best_prio is
only reset (in the loop) if CONFIG_FAIR_GROUP_SCHED is set.  This should
preserve the effect of helping spread groups' higher priority tasks
around the available CPUs while improving system performance when
CONFIG_FAIR_GROUP_SCHED isn't set.
Signed-off-by: NPeter Williams <pwil3058@bigpond.net.au>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

small delta_exec accounting fix: increase delta_exec and increase
sum_exec_runtime even if the task is not on the runqueue anymore.
Signed-off-by: NIngo Molnar <mingo@elte.hu>

cleanup: delta_mine is an unsigned value.

no code impact:

   text    data     bss     dec     hex filename
   27823    2726      16   30565    7765 sched.o.before
   27823    2726      16   30565    7765 sched.o.after
Signed-off-by: NIngo Molnar <mingo@elte.hu>

sched_fair.c defines print_cfs_stats, and sched_debug.c uses it, but sched.c
includes both sched_fair.c and sched_debug.c, so all the references to
print_cfs_stats occur in the same compilation unit.  Thus, mark
print_cfs_stats static.

Eliminates a sparse warning:
warning: symbol 'print_cfs_stats' was not declared. Should it be static?
Signed-off-by: NJosh Triplett <josh@kernel.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

The move_tasks() function is currently multiplexed with two distinct
capabilities:

1. attempt to move a specified amount of weighted load from one run
queue to another; and
2. attempt to move a specified number of tasks from one run queue to
another.

The first of these capabilities is used in two places, load_balance()
and load_balance_idle(), and in both of these cases the return value of
move_tasks() is used purely to decide if tasks/load were moved and no
notice of the actual number of tasks moved is taken.

The second capability is used in exactly one place,
active_load_balance(), to attempt to move exactly one task and, as
before, the return value is only used as an indicator of success or failure.

This multiplexing of sched_task() was introduced, by me, as part of the
smpnice patches and was motivated by the fact that the alternative, one
function to move specified load and one to move a single task, would
have led to two functions of roughly the same complexity as the old
move_tasks() (or the new balance_tasks()).  However, the new modular
design of the new CFS scheduler allows a simpler solution to be adopted
and this patch addresses that solution by:

1. adding a new function, move_one_task(), to be used by
active_load_balance(); and
2. making move_tasks() a single purpose function that tries to move a
specified weighted load and returns 1 for success and 0 for failure.

One of the consequences of these changes is that neither move_one_task()
or the new move_tasks() care how many tasks sched_class.load_balance()
moves and this enables its interface to be simplified by returning the
amount of load moved as its result and removing the load_moved pointer
from the argument list.  This helps simplify the new move_tasks() and
slightly reduces the amount of work done in each of
sched_class.load_balance()'s implementations.

Further simplification, e.g. changes to balance_tasks(), are possible
but (slightly) complicated by the special needs of load_balance_fair()
so I've left them to a later patch (if this one gets accepted).

NB Since move_tasks() gets called with two run queue locks held even
small reductions in overhead are worthwhile.

[ mingo@elte.hu ]

this change also reduces code size nicely:

   text    data     bss     dec     hex filename
   39216    3618      24   42858    a76a sched.o.before
   39173    3618      24   42815    a73f sched.o.after
Signed-off-by: NPeter Williams <pwil3058@bigpond.net.au>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

batch up the sleeper bonus sum a bit more. Anything below
sched-granularity is too small to make a practical difference
anyway.

this optimization reduces the math in high-frequency scheduling
scenarios.
Signed-off-by: NIngo Molnar <mingo@elte.hu>

move the rest of the debugging/instrumentation code to under
CONFIG_SCHEDSTATS too. This reduces code size and speeds code up:

    text    data     bss     dec     hex filename
   33044    4122      28   37194    914a sched.o.before
   32708    4122      28   36858    8ffa sched.o.after
Signed-off-by: NIngo Molnar <mingo@elte.hu>

make use of the new schedstat_set() API to eliminate two #ifdef sections.

No functional changes:

    text    data     bss     dec     hex filename
   29009    4122      28   33159    8187 sched.o.before
   29009    4122      28   33159    8187 sched.o.after
Signed-off-by: NIngo Molnar <mingo@elte.hu>

make sched_class.task_new == NULL a 'default method', this
allows the removal of task_rt_new.
Signed-off-by: NIngo Molnar <mingo@elte.hu>