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  1. 09 Aug, 2007 13 commits
    • Peter Williams's avatar
      sched: fix bug in balance_tasks() · a4ac01c3
      Peter Williams authored 
      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: default avatarPeter Williams <pwil3058@bigpond.net.au>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      a4ac01c3
    • Ingo Molnar's avatar
      sched: document nice levels · aea25401
      Ingo Molnar authored 
      Document the design thinking behind nice levels.
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      aea25401
    • Alexey Dobriyan's avatar
      sched: remove binary sysctls from kernel.sched_domain · e0361851
      Alexey Dobriyan authored 
      kernel.sched_domain hierarchy is under CTL_UNNUMBERED and thus
unreachable to sysctl(2). Generating .ctl_number's in such situation is
not useful.
Signed-off-by: default avatarAlexey Dobriyan <adobriyan@sw.ru>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      e0361851
    • Ingo Molnar's avatar
      sched: delta_exec accounting fix · fd8bb43e
      Ingo Molnar authored 
      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: default avatarIngo Molnar <mingo@elte.hu>
      fd8bb43e
    • Ingo Molnar's avatar
      sched: clean up delta_mine · c5dcfe72
      Ingo Molnar authored 
      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: default avatarIngo Molnar <mingo@elte.hu>
      c5dcfe72
    • Ingo Molnar's avatar
      sched: schedule() speedup · 8e717b19
      Ingo Molnar authored 
      speed up schedule(): share the 'now' parameter that deactivate_task()
was calculating internally.

( this also fixes the small accounting window between the deactivate
  call and the pick_next_task() call. )
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      8e717b19
    • Ingo Molnar's avatar
      sched: uninline rq_clock() · 7bfd0485
      Ingo Molnar authored 
      uninline rq_clock() to save 263 bytes of code:

   text    data     bss     dec     hex filename
   39561    3642      24   43227    a8db sched.o.before
   39298    3642      24   42964    a7d4 sched.o.after
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      7bfd0485
    • Josh Triplett's avatar
      sched: mark print_cfs_stats static · 291ae5a1
      Josh Triplett authored 
      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: default avatarJosh Triplett <josh@kernel.org>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      291ae5a1
    • Ulrich Drepper's avatar
      sched: clean up sched_getaffinity() · 9531b62f
      Ulrich Drepper authored 
      here's another tiny cleanup.  The generated code is not affected (gcc is
smart enough) but for people looking over the code it is just irritating
to have the extra conditional.
Signed-off-by: default avatarUlrich Drepper <drepper@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      9531b62f
    • Thomas Voegtle's avatar
      sched: mention CONFIG_SCHED_DEBUG in documentation · 5f5d3aa1
      Thomas Voegtle authored 
      a little hint to switch on CONFIG_SCHED_DEBUG should be given.
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      5f5d3aa1
    • Peter Williams's avatar
      sched: simplify move_tasks() · 43010659
      Peter Williams authored 
      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: default avatarPeter Williams <pwil3058@bigpond.net.au>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      43010659
    • Ingo Molnar's avatar
      sched: reorder update_cpu_load(rq) with the ->task_tick() call · f1a438d8
      Ingo Molnar authored 
      Peter Williams suggested to flip the order of update_cpu_load(rq) with
the ->task_tick() call. This is a NOP for the current scheduler (the
two functions are independent of each other), ->task_tick() might
create some state for update_cpu_load() in the future (or in PlugSched).
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      f1a438d8
    • Ingo Molnar's avatar
      sched: batch sleeper bonus · 0915c4e8
      Ingo Molnar authored 
      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: default avatarIngo Molnar <mingo@elte.hu>
      0915c4e8
  3. 07 Aug, 2007 9 commits
  5. 06 Aug, 2007 3 commits
  7. 05 Aug, 2007 2 commits
  9. 04 Aug, 2007 13 commits