improve the rq-clock overflow logic: limit the absolute rq->clock
delta since the last scheduler tick, instead of limiting the delta
itself.
tested by Arjan van de Ven - whole laptop was misbehaving due to
an incorrectly calibrated cpu_khz confusing sched_clock().
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
round a tiny bit better in high-frequency rescheduling scenarios,
by rounding around zero instead of rounding down.
(this is pretty theoretical though)
Signed-off-by: Ingo Molnar <mingo@elte.hu>
optimize update_rq_clock() calls in the load-balancer: update them
right after locking the runqueue(s) so that the pull functions do
not have to call it.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
optimize activate_task() by removing update_rq_clock() from it.
(and add update_rq_clock() to all callsites of activate_task() that
did not have it before.)
Signed-off-by: Ingo Molnar <mingo@elte.hu>
move the __update_rq_clock() call from update_cpu_load() to
scheduler_tick().
( identity transformation that causes no change in functionality. )
this allows the direct use of rq->clock in ->task_tick() functions.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
final step: remove all (now superfluous) 'u64 now' variables.
( identity transformation that causes no change in functionality. )
Signed-off-by: Ingo Molnar <mingo@elte.hu>
remove the 'u64 now' parameter from deactivate_task().
( identity transformation that causes no change in functionality. )
Signed-off-by: Ingo Molnar <mingo@elte.hu>
remove the 'u64 now' parameter from dequeue_task().
( identity transformation that causes no change in functionality. )
Signed-off-by: Ingo Molnar <mingo@elte.hu>
remove the 'u64 now' parameter from enqueue_task().
( identity transformation that causes no change in functionality. )
Signed-off-by: Ingo Molnar <mingo@elte.hu>
remove the 'u64 now' parameter from dec_nr_running().
( identity transformation that causes no change in functionality. )
Signed-off-by: Ingo Molnar <mingo@elte.hu>
remove the 'u64 now' parameter from inc_nr_running().
( identity transformation that causes no change in functionality. )
Signed-off-by: Ingo Molnar <mingo@elte.hu>
remove the 'u64 now' parameter from dec_load().
( identity transformation that causes no change in functionality. )
Signed-off-by: Ingo Molnar <mingo@elte.hu>
remove the 'u64 now' parameter from inc_load().
( identity transformation that causes no change in functionality. )
Signed-off-by: Ingo Molnar <mingo@elte.hu>
remove the 'u64 now' parameter from update_curr_load().
( identity transformation that causes no change in functionality. )
Signed-off-by: Ingo Molnar <mingo@elte.hu>
remove the 'u64 now' parameter from ->task_new().
( identity transformation that causes no change in functionality. )
Signed-off-by: Ingo Molnar <mingo@elte.hu>
remove the 'u64 now' parameter from ->put_prev_task().
( identity transformation that causes no change in functionality. )
Signed-off-by: Ingo Molnar <mingo@elte.hu>
remove the 'u64 now' parameter from pick_next_task().
( identity transformation that causes no change in functionality. )
Signed-off-by: Ingo Molnar <mingo@elte.hu>
remove the 'u64 now' parameter from ->pick_next_task().
( identity transformation that causes no change in functionality. )
Signed-off-by: Ingo Molnar <mingo@elte.hu>
remove the 'u64 now' parameter from ->dequeue_task().
( identity transformation that causes no change in functionality. )
Signed-off-by: Ingo Molnar <mingo@elte.hu>
remove the 'u64 now' parameter from ->enqueue_task().
( identity transformation that causes no change in functionality. )
Signed-off-by: Ingo 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: Ingo 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: Ingo 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: Ingo Molnar <mingo@elte.hu>
add the [__]update_rq_clock(rq) functions. (No change in functionality,
just reorganization to prepare for elimination of the heavy 64-bit
timestamp-passing in the scheduler.)
Signed-off-by: Ingo 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: Peter Williams <pwil3058@bigpond.net.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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: Alexey Dobriyan <adobriyan@sw.ru>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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: Ingo Molnar <mingo@elte.hu>
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: Ingo Molnar <mingo@elte.hu>
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: Ulrich Drepper <drepper@redhat.com>
Signed-off-by: Ingo 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: Peter Williams <pwil3058@bigpond.net.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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: Ingo 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: Ingo Molnar <mingo@elte.hu>
1. The only place that RTPRIO_TO_LOAD_WEIGHT() is used is in the call to
move_tasks() in the function active_load_balance() and its purpose here
is just to make sure that the load to be moved is big enough to ensure
that exactly one task is moved (if there's one available). This can be
accomplished by using ULONG_MAX instead and this allows
RTPRIO_TO_LOAD_WEIGHT() to be deleted.
2. This, in turn, allows PRIO_TO_LOAD_WEIGHT() to be deleted.
3. This allows load_weight() to be deleted which allows
TIME_SLICE_NICE_ZERO to be deleted along with the comment above it.
Signed-off-by: Peter Williams <pwil3058@bigpond.net.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Fix kernel-doc warnings in sched.c:
Warning(linux-2623-rc1g4//kernel/sched.c:1685): No description found for parameter 'notifier'
Warning(linux-2623-rc1g4//kernel/sched.c:1696): No description found for parameter 'notifier'
Warning(linux-2623-rc1g4//kernel/sched.c:1750): No description found for parameter 'prev'
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
debugging feature: make the sched-domains tree runtime-tweakable.
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
[ mingo@elte.hu: made it depend on CONFIG_SCHED_DEBUG & small updates ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
it is enough to disable interrupts to get the precise rq-clock
of the local CPU.
this also solves an NMI watchdog regression: the NMI watchdog
calls touch_softlockup_watchdog(), which might deadlock on
rq->lock if the NMI hits an rq-locked critical section.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This adds a general mechanism whereby a task can request the scheduler to
notify it whenever it is preempted or scheduled back in. This allows the
task to swap any special-purpose registers like the fpu or Intel's VT
registers.
Signed-off-by: Avi Kivity <avi@qumranet.com>
[ mingo@elte.hu: fixes, cleanups ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Implement the cpu_clock(cpu) interface for kernel-internal use:
high-speed (but slightly incorrect) per-cpu clock constructed from
sched_clock().
This API, unused at the moment, will be used in the future by blktrace,
by the softlockup-watchdog, by printk and by lockstat.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
nr_moved is not the correct check for triggering all pinned logic. Fix
the all pinned logic in the case of load_balance_newidle().
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
In the presence of SMT, newly idle balance was never happening for
multi-core and SMP domains (even when both the logical siblings are
idle).
If thread 0 is already idle and when thread 1 is about to go to idle,
newly idle load balance always think that one of the threads is not idle
and skips doing the newly idle load balance for multi-core and SMP
domains.
This is because of the idle_cpu() macro, which checks if the current
process on a cpu is an idle process. But this is not the case for the
thread doing the load_balance_newidle().
Fix this by using runqueue's nr_running field instead of idle_cpu(). And
also skip the logic of 'only one idle cpu in the group will be doing
load balancing' during newly idle case.
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
