Commit graph

375 commits

Author SHA1 Message Date
Tejun Heo
969c79215a sched: replace migration_thread with cpu_stop
Currently migration_thread is serving three purposes - migration
pusher, context to execute active_load_balance() and forced context
switcher for expedited RCU synchronize_sched.  All three roles are
hardcoded into migration_thread() and determining which job is
scheduled is slightly messy.

This patch kills migration_thread and replaces all three uses with
cpu_stop.  The three different roles of migration_thread() are
splitted into three separate cpu_stop callbacks -
migration_cpu_stop(), active_load_balance_cpu_stop() and
synchronize_sched_expedited_cpu_stop() - and each use case now simply
asks cpu_stop to execute the callback as necessary.

synchronize_sched_expedited() was implemented with private
preallocated resources and custom multi-cpu queueing and waiting
logic, both of which are provided by cpu_stop.
synchronize_sched_expedited_count is made atomic and all other shared
resources along with the mutex are dropped.

synchronize_sched_expedited() also implemented a check to detect cases
where not all the callback got executed on their assigned cpus and
fall back to synchronize_sched().  If called with cpu hotplug blocked,
cpu_stop already guarantees that and the condition cannot happen;
otherwise, stop_machine() would break.  However, this patch preserves
the paranoid check using a cpumask to record on which cpus the stopper
ran so that it can serve as a bisection point if something actually
goes wrong theree.

Because the internal execution state is no longer visible,
rcu_expedited_torture_stats() is removed.

This patch also renames cpu_stop threads to from "stopper/%d" to
"migration/%d".  The names of these threads ultimately don't matter
and there's no reason to make unnecessary userland visible changes.

With this patch applied, stop_machine() and sched now share the same
resources.  stop_machine() is faster without wasting any resources and
sched migration users are much cleaner.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Dipankar Sarma <dipankar@in.ibm.com>
Cc: Josh Triplett <josh@freedesktop.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Dimitri Sivanich <sivanich@sgi.com>
2010-05-06 18:49:21 +02:00
Suresh Siddha
99bd5e2f24 sched: Fix select_idle_sibling() logic in select_task_rq_fair()
Issues in the current select_idle_sibling() logic in select_task_rq_fair()
in the context of a task wake-up:

a) Once we select the idle sibling, we use that domain (spanning the cpu that
   the task is currently woken-up and the idle sibling that we found) in our
   wake_affine() decisions. This domain is completely different from the
   domain(we are supposed to use) that spans the cpu that the task currently
   woken-up and the cpu where the task previously ran.

b) We do select_idle_sibling() check only for the cpu that the task is
   currently woken-up on. If select_task_rq_fair() selects the previously run
   cpu for waking the task, doing a select_idle_sibling() check
   for that cpu also helps and we don't do this currently.

c) In the scenarios where the cpu that the task is woken-up is busy but
   with its HT siblings are idle, we are selecting the task be woken-up
   on the idle HT sibling instead of a core that it previously ran
   and currently completely idle. i.e., we are not taking decisions based on
   wake_affine() but directly selecting an idle sibling that can cause
   an imbalance at the SMT/MC level which will be later corrected by the
   periodic load balancer.

Fix this by first going through the load imbalance calculations using
wake_affine() and once we make a decision of woken-up cpu vs previously-ran cpu,
then choose a possible idle sibling for waking up the task on.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1270079265.7835.8.camel@sbs-t61.sc.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-04-23 11:02:02 +02:00
Peter Zijlstra
669c55e9f9 sched: Pre-compute cpumask_weight(sched_domain_span(sd))
Dave reported that his large SPARC machines spend lots of time in
hweight64(), try and optimize some of those needless cpumask_weight()
invocations (esp. with the large offstack cpumasks these are very
expensive indeed).

Reported-by: David Miller <davem@davemloft.net>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-04-23 11:02:02 +02:00
Peter Zijlstra
371fd7e7a5 sched: Add enqueue/dequeue flags
In order to reduce the dependency on TASK_WAKING rework the enqueue
interface to support a proper flags field.

Replace the int wakeup, bool head arguments with an int flags argument
and create the following flags:

  ENQUEUE_WAKEUP - the enqueue is a wakeup of a sleeping task,
  ENQUEUE_WAKING - the enqueue has relative vruntime due to
                   having sched_class::task_waking() called,
  ENQUEUE_HEAD - the waking task should be places on the head
                 of the priority queue (where appropriate).

For symmetry also convert sched_class::dequeue() to a flags scheme.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-04-02 20:12:05 +02:00
Peter Zijlstra
0017d73509 sched: Fix TASK_WAKING vs fork deadlock
Oleg noticed a few races with the TASK_WAKING usage on fork.

 - since TASK_WAKING is basically a spinlock, it should be IRQ safe
 - since we set TASK_WAKING (*) without holding rq->lock it could
   be there still is a rq->lock holder, thereby not actually
   providing full serialization.

(*) in fact we clear PF_STARTING, which in effect enables TASK_WAKING.

Cure the second issue by not setting TASK_WAKING in sched_fork(), but
only temporarily in wake_up_new_task() while calling select_task_rq().

Cure the first by holding rq->lock around the select_task_rq() call,
this will disable IRQs, this however requires that we push down the
rq->lock release into select_task_rq_fair()'s cgroup stuff.

Because select_task_rq_fair() still needs to drop the rq->lock we
cannot fully get rid of TASK_WAKING.

Reported-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-04-02 20:12:03 +02:00
Ingo Molnar
c9494727cf Merge branch 'linus' into sched/core
Merge reason: update to latest upstream

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-04-02 20:03:08 +02:00
Mike Galbraith
beac4c7e4a sched: Remove AFFINE_WAKEUPS feature
Disabling affine wakeups is too horrible to contemplate.  Remove the feature flag.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1268301890.6785.50.camel@marge.simson.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-03-11 18:32:53 +01:00
Mike Galbraith
13814d42e4 sched: Remove ASYM_GRAN feature
This features has been enabled for quite a while, after testing showed that
easing preemption for light tasks was harmful to high priority threads.

Remove the feature flag.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1268301675.6785.44.camel@marge.simson.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-03-11 18:32:53 +01:00
Mike Galbraith
f2e74eeac0 sched: Remove WAKEUP_SYNC feature
This feature never earned its keep, remove it.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1268301591.6785.42.camel@marge.simson.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-03-11 18:32:52 +01:00
Mike Galbraith
5ca9880c6f sched: Remove FAIR_SLEEPERS feature
Our preemption model relies too heavily on sleeper fairness to disable it
without dire consequences.  Remove the feature, and save a branch or two.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1268301520.6785.40.camel@marge.simson.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-03-11 18:32:52 +01:00
Mike Galbraith
6bc6cf2b61 sched: Remove NORMALIZED_SLEEPER
This feature hasn't been enabled in a long time, remove effectively dead code.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1268301447.6785.38.camel@marge.simson.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-03-11 18:32:52 +01:00
Mike Galbraith
8b911acdf0 sched: Fix select_idle_sibling()
Don't bother with selection when the current cpu is idle.  Recent load
balancing changes also make it no longer necessary to check wake_affine()
success before returning the selected sibling, so we now always use it.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1268301369.6785.36.camel@marge.simson.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-03-11 18:32:51 +01:00
Mike Galbraith
21406928af sched: Tweak sched_latency and min_granularity
Allow LAST_BUDDY to kick in sooner, improving cache utilization as soon as
a second buddy pair arrives on scene.  The cost is latency starting to climb
sooner, the tbenefit for tbench 8 on my Q6600 box is ~2%.  No detrimental
effects noted in normal idesktop usage.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1268301285.6785.34.camel@marge.simson.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-03-11 18:32:51 +01:00
Mike Galbraith
a64692a3af sched: Cleanup/optimize clock updates
Now that we no longer depend on the clock being updated prior to enqueueing
on migratory wakeup, we can clean up a bit, placing calls to update_rq_clock()
exactly where they are needed, ie on enqueue, dequeue and schedule events.

In the case of a freshly enqueued task immediately preempting, we can skip the
update during preemption, as the clock was just updated by the enqueue event.
We also save an unneeded call during a migratory wakeup by not updating the
previous runqueue, where update_curr() won't be invoked.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1268301199.6785.32.camel@marge.simson.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-03-11 18:32:50 +01:00
Mike Galbraith
e12f31d3e5 sched: Remove avg_overlap
Both avg_overlap and avg_wakeup had an inherent problem in that their accuracy
was detrimentally affected by cross-cpu wakeups, this because we are missing
the necessary call to update_curr().  This can't be fixed without increasing
overhead in our already too fat fastpath.

Additionally, with recent load balancing changes making us prefer to place tasks
in an idle cache domain (which is good for compute bound loads), communicating
tasks suffer when a sync wakeup, which would enable affine placement, is turned
into a non-sync wakeup by SYNC_LESS.  With one task on the runqueue, wake_affine()
rejects the affine wakeup request, leaving the unfortunate where placed, taking
frequent cache misses.

Remove it, and recover some fastpath cycles.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1268301121.6785.30.camel@marge.simson.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-03-11 18:32:50 +01:00
Mike Galbraith
b42e0c41a4 sched: Remove avg_wakeup
Testing the load which led to this heuristic (nfs4 kbuild) shows that it has
outlived it's usefullness.  With intervening load balancing changes, I cannot
see any difference with/without, so recover there fastpath cycles.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1268301062.6785.29.camel@marge.simson.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-03-11 18:32:50 +01:00
Lucas De Marchi
41acab8851 sched: Implement group scheduler statistics in one struct
Put all statistic fields of sched_entity in one struct, sched_statistics,
and embed it into sched_entity.

This change allows to memset the sched_statistics to 0 when needed (for
instance when forking), avoiding bugs of non initialized fields.

Signed-off-by: Lucas De Marchi <lucas.de.marchi@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1268275065-18542-1-git-send-email-lucas.de.marchi@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-03-11 15:22:28 +01:00
Paul E. McKenney
90a6501f94 sched, rcu: Fix rcu_dereference() for RCU-lockdep
Make rcu_dereference() of runqueue data structures be
rcu_dereference_sched().

Located-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
LKML-Reference: <20100228163218.GD6846@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-03-01 09:29:58 +01:00
Suresh Siddha
dd5feea14a sched: Fix SCHED_MC regression caused by change in sched cpu_power
On platforms like dual socket quad-core platform, the scheduler load
balancer is not detecting the load imbalances in certain scenarios. This
is leading to scenarios like where one socket is completely busy (with
all the 4 cores running with 4 tasks) and leaving another socket
completely idle. This causes performance issues as those 4 tasks share
the memory controller, last-level cache bandwidth etc. Also we won't be
taking advantage of turbo-mode as much as we would like, etc.

Some of the comparisons in the scheduler load balancing code are
comparing the "weighted cpu load that is scaled wrt sched_group's
cpu_power" with the "weighted average load per task that is not scaled
wrt sched_group's cpu_power". While this has probably been broken for a
longer time (for multi socket numa nodes etc), the problem got aggrevated
via this recent change:

 |
 |  commit f93e65c186
 |  Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
 |  Date:   Tue Sep 1 10:34:32 2009 +0200
 |
 |	sched: Restore __cpu_power to a straight sum of power
 |

Also with this change, the sched group cpu power alone no longer reflects
the group capacity that is needed to implement MC, MT performance
(default) and power-savings (user-selectable) policies.

We need to use the computed group capacity (sgs.group_capacity, that is
computed using the SD_PREFER_SIBLING logic in update_sd_lb_stats()) to
find out if the group with the max load is above its capacity and how
much load to move etc.

Reported-by: Ma Ling <ling.ma@intel.com>
Initial-Analysis-by: Zhang, Yanmin <yanmin_zhang@linux.intel.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
[ -v2: build fix ]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: <stable@kernel.org> # [2.6.32.x, 2.6.33.x]
LKML-Reference: <1266970432.11588.22.camel@sbs-t61.sc.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-02-26 15:45:13 +01:00
Thomas Gleixner
6e40f5bbbc Merge branch 'sched/urgent' into sched/core
Conflicts: kernel/sched.c

Necessary due to the urgent fixes which conflict with the code move
from sched.c to sched_fair.c

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2010-02-16 16:48:56 +01:00
Ingo Molnar
6d3e0907b8 Merge branch 'sched/urgent' into sched/core
Merge reason: Merge dependent fix, update to latest -rc.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-02-08 08:55:46 +01:00
Thomas Gleixner
ea87bb7853 sched: Extend enqueue_task to allow head queueing
The ability of enqueueing a task to the head of a SCHED_FIFO priority
list is required to fix some violations of POSIX scheduling policy.

Extend the related functions with a "head" argument.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Tested-by: Carsten Emde <cbe@osadl.org>
Tested-by: Mathias Weber <mathias.weber.mw1@roche.com>
LKML-Reference: <20100120171629.734886007@linutronix.de>
2010-01-22 18:09:59 +01:00
Gautham R Shenoy
871e35bc97 sched: Fix the place where group powers are updated
We want to update the sched_group_powers when balance_cpu == this_cpu.

Currently the group powers are updated only if the balance_cpu is the
first CPU in the local group. But balance_cpu = this_cpu could also be
the first idle cpu in the group. Hence fix the place where the group
powers are updated.

Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Joel Schopp <jschopp@austin.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1264017764.5717.127.camel@jschopp-laptop>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-01-21 13:40:17 +01:00
Peter Zijlstra
8f190fb3f7 sched: Assume *balance is valid
Since all load_balance() callers will have !NULL balance parameters we
can now assume so and remove a few checks.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-01-21 13:40:15 +01:00
Peter Zijlstra
f492e12ef0 sched: Remove load_balance_newidle()
The two functions: load_balance{,_newidle}() are very similar, with the
following differences:

 - rq->lock usage
 - sb->balance_interval updates
 - *balance check

So remove the load_balance_newidle() call with load_balance(.idle =
CPU_NEWLY_IDLE), explicitly unlock the rq->lock before calling (would be
done by double_lock_balance() anyway), and ignore the other differences
for now.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-01-21 13:40:14 +01:00
Peter Zijlstra
1af3ed3ddf sched: Unify load_balance{,_newidle}()
load_balance() and load_balance_newidle() look remarkably similar, one
key point they differ in is the condition on when to active balance.

So split out that logic into a separate function.

One side effect is that previously load_balance_newidle() used to fail
and return -1 under these conditions, whereas now it doesn't. I've not
yet fully figured out the whole -1 return case for either
load_balance{,_newidle}().

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-01-21 13:40:13 +01:00
Peter Zijlstra
baa8c1102f sched: Add a lock break for PREEMPT=y
Since load-balancing can hold rq->locks for quite a long while, allow
breaking out early when there is lock contention.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-01-21 13:40:13 +01:00
Peter Zijlstra
230059de77 sched: Remove from fwd decls
Move code around to get rid of fwd declarations.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-01-21 13:40:12 +01:00
Peter Zijlstra
897c395f4c sched: Remove rq_iterator from move_one_task
Again, since we only iterate the fair class, remove the abstraction.

Since this is the last user of the rq_iterator, remove all that too.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-01-21 13:40:11 +01:00
Peter Zijlstra
ee00e66fff sched: Remove rq_iterator usage from load_balance_fair
Since we only ever iterate the fair class, do away with this abstraction.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-01-21 13:40:10 +01:00
Peter Zijlstra
3d45fd804a sched: Remove the sched_class load_balance methods
Take out the sched_class methods for load-balancing.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-01-21 13:40:09 +01:00
Peter Zijlstra
1e3c88bdeb sched: Move load balance code into sched_fair.c
Straight fwd code movement.

Since non of the load-balance abstractions are used anymore, do away with
them and simplify the code some. In preparation move the code around.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-01-21 13:40:08 +01:00
Mike Galbraith
50b926e439 sched: Fix vmark regression on big machines
SD_PREFER_SIBLING is set at the CPU domain level if power saving isn't
enabled, leading to many cache misses on large machines as we traverse
looking for an idle shared cache to wake to.  Change the enabler of
select_idle_sibling() to SD_SHARE_PKG_RESOURCES, and enable same at the
sibling domain level.

Reported-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1262612696.15495.15.camel@marge.simson.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-01-21 13:39:03 +01:00
H Hartley Sweeten
6d686f4564 sched: Don't expose local functions
kernel/sched: don't expose local functions

The get_rr_interval_* functions are all class methods of
struct sched_class. They are not exported so make them
static.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Peter Zijlstra <peterz@infradead.org>
LKML-Reference: <201001132021.53253.hartleys@visionengravers.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2010-01-17 08:09:45 +01:00
Peter Zijlstra
88ec22d3ed sched: Remove the cfs_rq dependency from set_task_cpu()
In order to remove the cfs_rq dependency from set_task_cpu() we
need to ensure the task is cfs_rq invariant for all callsites.

The simple approach is to substract cfs_rq->min_vruntime from
se->vruntime on dequeue, and add cfs_rq->min_vruntime on
enqueue.

However, this has the downside of breaking FAIR_SLEEPERS since
we loose the old vruntime as we only maintain the relative
position.

To solve this, we observe that we only migrate runnable tasks,
we do this using deactivate_task(.sleep=0) and
activate_task(.wakeup=0), therefore we can restrain the
min_vruntime invariance to that state.

The only other case is wakeup balancing, since we want to
maintain the old vruntime we cannot make it relative on dequeue,
but since we don't migrate inactive tasks, we can do so right
before we activate it again.

This is where we need the new pre-wakeup hook, we need to call
this while still holding the old rq->lock. We could fold it into
->select_task_rq(), but since that has multiple callsites and
would obfuscate the locking requirements, that seems like a
fudge.

This leaves the fork() case, simply make sure that ->task_fork()
leaves the ->vruntime in a relative state.

This covers all cases where set_task_cpu() gets called, and
ensures it sees a relative vruntime.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
LKML-Reference: <20091216170518.191697025@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-12-16 19:01:58 +01:00
Peter Zijlstra
e4f4288842 sched: Select_task_rq_fair() must honour SD_LOAD_BALANCE
We should skip !SD_LOAD_BALANCE domains.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
LKML-Reference: <20091216170517.653578430@chello.nl>
CC: stable@kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-12-16 19:01:55 +01:00
Thomas Gleixner
05fa785cf8 sched: Convert rq->lock to raw_spinlock
Convert locks which cannot be sleeping locks in preempt-rt to
raw_spinlocks.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
2009-12-14 23:55:33 +01:00
Christian Ehrhardt
acb4a848da sched: Update normalized values on user updates via proc
The normalized values are also recalculated in case the scaling factor
changes.

This patch updates the internally used scheduler tuning values that are
normalized to one cpu in case a user sets new values via sysfs.

Together with patch 2 of this series this allows to let user configured
values scale (or not) to cpu add/remove events taking place later.

Signed-off-by: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1259579808-11357-4-git-send-email-ehrhardt@linux.vnet.ibm.com>
[ v2: fix warning ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-12-09 10:04:02 +01:00
Christian Ehrhardt
1983a922a1 sched: Make tunable scaling style configurable
As scaling now takes place on all kind of cpu add/remove events a user
that configures values via proc should be able to configure if his set
values are still rescaled or kept whatever happens.

As the comments state that log2 was just a second guess that worked the
interface is not just designed for on/off, but to choose a scaling type.
Currently this allows none, log and linear, but more important it allwos
us to keep the interface even if someone has an even better idea how to
scale the values.

Signed-off-by: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1259579808-11357-3-git-send-email-ehrhardt@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-12-09 10:04:01 +01:00
Christian Ehrhardt
0bcdcf28c9 sched: Fix missing sched tunable recalculation on cpu add/remove
Based on Peter Zijlstras patch suggestion this enables recalculation of
the scheduler tunables in response of a change in the number of cpus. It
also adds a max of eight cpus that are considered in that scaling.

Signed-off-by: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1259579808-11357-2-git-send-email-ehrhardt@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-12-09 10:03:58 +01:00
Peter Zijlstra
fb58bac5c7 sched: Remove unnecessary RCU exclusion
As Nick pointed out, and realized by myself when doing:
   sched: Fix balance vs hotplug race
the patch:
   sched: for_each_domain() vs RCU

is wrong, sched_domains are freed after synchronize_sched(), which
means disabling preemption is enough.

Reported-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-12-09 10:03:08 +01:00
Peter Zijlstra
6cecd084d0 sched: Discard some old bits
WAKEUP_RUNNING was an experiment, not sure why that ever ended up being
merged...

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-12-09 10:03:07 +01:00
Peter Zijlstra
3a7e73a2e2 sched: Clean up check_preempt_wakeup()
Streamline the wakeup preemption code a bit, unifying the preempt path
so that they all do the same.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-12-09 10:03:07 +01:00
Jupyung Lee
a65ac745e4 sched: Move update_curr() in check_preempt_wakeup() to avoid redundant call
If a RT task is woken up while a non-RT task is running,
check_preempt_wakeup() is called to check whether the new task can
preempt the old task. The function returns quickly without going deeper
because it is apparent that a RT task can always preempt a non-RT task.

In this situation, check_preempt_wakeup() always calls update_curr() to
update vruntime value of the currently running task. However, the
function call is unnecessary and redundant at that moment because (1) a
non-RT task can always be preempted by a RT task regardless of its
vruntime value, and (2) update_curr() will be called shortly when the
context switch between two occurs.

By moving update_curr() in check_preempt_wakeup(), we can avoid
redundant call to update_curr(), slightly reducing the time taken to
wake up RT tasks.

Signed-off-by: Jupyung Lee <jupyung@gmail.com>
[ Place update_curr() right before the wake_preempt_entity() call, which
  is the only thing that relies on the updated vruntime ]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1258451500-6714-1-git-send-email-jupyung@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-12-09 10:03:06 +01:00
Peter Zijlstra
cd29fe6f26 sched: Sanitize fork() handling
Currently we try to do task placement in wake_up_new_task() after we do
the load-balance pass in sched_fork(). This yields complicated semantics
in that we have to deal with tasks on different RQs and the
set_task_cpu() calls in copy_process() and sched_fork()

Rename ->task_new() to ->task_fork() and call it from sched_fork()
before the balancing, this gives the policy a clear point to place the
task.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-12-09 10:03:05 +01:00
Thomas Gleixner
dba091b9e3 sched: Protect sched_rr_get_param() access to task->sched_class
sched_rr_get_param calls
task->sched_class->get_rr_interval(task) without protection
against a concurrent sched_setscheduler() call which modifies
task->sched_class.

Serialize the access with task_rq_lock(task) and hand the rq
pointer into get_rr_interval() as it's needed at least in the
sched_fair implementation.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
LKML-Reference: <alpine.LFD.2.00.0912090930120.3089@localhost.localdomain>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-12-09 10:01:07 +01:00
Ingo Molnar
16bc67edeb Merge branch 'sched/urgent' into sched/core
Merge reason: Pick up fixes that did not make it into .32.0

Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-11-26 10:50:42 +01:00
Tim Blechmann
36ace27e3e sched: Optimize branch hint in pick_next_task_fair()
Branch hint profiling on my nehalem machine showed 90%
incorrect branch hints:

  15728471 158903754  90 pick_next_task_fair
  sched_fair.c    1555

Signed-off-by: Tim Blechmann <tim@klingt.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4B0BBBB1.2050100@klingt.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-11-24 12:18:12 +01:00
Peter Zijlstra
fe3bcfe1f6 sched: More generic WAKE_AFFINE vs select_idle_sibling()
Instead of only considering SD_WAKE_AFFINE | SD_PREFER_SIBLING
domains also allow all SD_PREFER_SIBLING domains below a
SD_WAKE_AFFINE domain to change the affinity target.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
LKML-Reference: <20091112145610.909723612@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-11-13 10:09:59 +01:00
Peter Zijlstra
a50bde5130 sched: Cleanup select_task_rq_fair()
Clean up the new affine to idle sibling bits while trying to
grok them. Should not have any function differences.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
LKML-Reference: <20091112145610.832503781@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-11-13 10:09:58 +01:00