| Message ID | 20191211173829.GB21797@linux.vnet.ibm.com (mailing list archive) |
|---|---|
| State | Deferred, archived |
| Headers | show |
| Series | [v4] sched/core: Preempt current task in favour of bound kthread | expand |
On Wed, Dec 11, 2019 at 11:08:29PM +0530, Srikar Dronamraju wrote: > A running task can wake-up a per CPU bound kthread on the same CPU. > If the current running task doesn't yield the CPU before the next load > balance operation, the scheduler would detect load imbalance and try to > balance the load. However this load balance would fail as the waiting > task is CPU bound, while the running task cannot be moved by the regular > load balancer. Finally the active load balancer would kick in and move > the task to a different CPU/Core. Moving the task to a different > CPU/core can lead to loss in cache affinity leading to poor performance. > > This is more prone to happen if the current running task is CPU > intensive and the sched_wake_up_granularity is set to larger value. > When the sched_wake_up_granularity was relatively small, it was observed > that the bound thread would complete before the load balancer would have > chosen to move the cache hot task to a different CPU. > > To deal with this situation, the current running task would yield to a > per CPU bound kthread, provided kthread is not CPU intensive. So a question for you here: when does the workqueue worker pre-empt the currently running task? Is it immediately? Or when a time-slice of the currently running task runs out? We don't want queued work immediately pre-empting the task that queued the work - the queued work is *deferred* work that should be run _soon_ but we want the currently running task to finish what it is doing first if possible. i.e. these are not synchronous wakeups, and so we shouldn't schedule kworker threads as though they are sync wakeups. That will affect batch processing effciency and reduce throughput because it will greatly increase the number of unnecessary context switches during IO completion processing.... > /pboffline/hwcct_prg_old/lib/fsperf -t overwrite --noclean -f 5g -b 4k /pboffline > > (With sched_wake_up_granularity set to 15ms) > > Performance counter stats for 'system wide' (5 runs): > event v5.4 v5.4 + patch(v3) > probe:active_load_balance_cpu_stop 1,919 ( +- 2.89% ) 4 ( +- 20.48% ) > sched:sched_waking 441,535 ( +- 0.17% ) 914,630 ( +- 0.18% ) > sched:sched_wakeup 441,533 ( +- 0.17% ) 914,630 ( +- 0.18% ) > sched:sched_wakeup_new 2,436 ( +- 8.08% ) 545 ( +- 4.02% ) > sched:sched_switch 797,007 ( +- 0.26% ) 1,490,261 ( +- 0.10% ) > sched:sched_migrate_task 20,998 ( +- 1.04% ) 2,492 ( +- 11.56% ) As we see here. We've doubled the number of context switches (increased by 700,000) just to avoid 17,000 incorrect load balancer task migrations. That seems like we now make 700,000 incorrect decisions instead of just 20,000. The difference is that the consequence of making these many incorrect pre-emption decisions is vastly less than the consequence of making the wrong migration decision. It seems to me that we should be checking this is_per_cpu_kthread() state for tasks queued on the runqueue during active load balancing, rather than at wakeup time. i.e. in these cases we don't migrate the running task, we just let it run out it's timeslice out and the local per-cpu kthreads then run appropriately. AFAICT this would have the same effect of avoiding unnecessary task migrations in this workload, but without causing a global change to the way workqueue kworkers are scheduled that has the potential to cause regressions in other workqueue intensive workloads.... Cheers, Dave.
On Thu, Dec 12, 2019 at 09:46:17AM +1100, Dave Chinner wrote: > On Wed, Dec 11, 2019 at 11:08:29PM +0530, Srikar Dronamraju wrote: > > A running task can wake-up a per CPU bound kthread on the same CPU. > > If the current running task doesn't yield the CPU before the next load > > balance operation, the scheduler would detect load imbalance and try to > > balance the load. However this load balance would fail as the waiting > > task is CPU bound, while the running task cannot be moved by the regular > > load balancer. Finally the active load balancer would kick in and move > > the task to a different CPU/Core. Moving the task to a different > > CPU/core can lead to loss in cache affinity leading to poor performance. > > > > This is more prone to happen if the current running task is CPU > > intensive and the sched_wake_up_granularity is set to larger value. > > When the sched_wake_up_granularity was relatively small, it was observed > > that the bound thread would complete before the load balancer would have > > chosen to move the cache hot task to a different CPU. > > > > To deal with this situation, the current running task would yield to a > > per CPU bound kthread, provided kthread is not CPU intensive. > > So a question for you here: when does the workqueue worker pre-empt > the currently running task? Is it immediately? Or when a time-slice > of the currently running task runs out? > > We don't want queued work immediately pre-empting the task that > queued the work - the queued work is *deferred* work that should be > run _soon_ but we want the currently running task to finish what it > is doing first if possible. Good point, something to maybe try (Srikar?) is making tick preemption more agressive for such tasks. The below extends the previous patch to retain the set_next_buddy() on wakeup, but does not make the actual preemption more agressive. Then it 'fixes' the tick preemption to better align with the actual scheduler pick (ie. consider the buddy hints). --- kernel/sched/core.c | 3 +++ kernel/sched/fair.c | 26 +++++++++++++++++++------- kernel/sched/sched.h | 3 ++- 3 files changed, 24 insertions(+), 8 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 90e4b00ace89..75738b136ea7 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2560,6 +2560,9 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags) success = 1; cpu = task_cpu(p); + if (is_per_cpu_kthread(p)) + wake_flags |= WF_KTHREAD; + /* * Ensure we load p->on_rq _after_ p->state, otherwise it would * be possible to, falsely, observe p->on_rq == 0 and get stuck diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 08a233e97a01..78e681c8c19a 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4126,6 +4126,9 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) update_min_vruntime(cfs_rq); } +static struct sched_entity * +__pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr); + /* * Preempt the current task with a newly woken task if needed: */ @@ -4156,13 +4159,13 @@ check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr) if (delta_exec < sysctl_sched_min_granularity) return; - se = __pick_first_entity(cfs_rq); + se = __pick_next_entity(cfs_rq, NULL); delta = curr->vruntime - se->vruntime; if (delta < 0) return; - if (delta > ideal_runtime) + if (delta > ideal_runtime) // maybe frob this too ? resched_curr(rq_of(cfs_rq)); } @@ -4210,7 +4213,7 @@ wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se); * 4) do not run the "skip" process, if something else is available */ static struct sched_entity * -pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr) +__pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr) { struct sched_entity *left = __pick_first_entity(cfs_rq); struct sched_entity *se; @@ -4255,8 +4258,14 @@ pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr) if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1) se = cfs_rq->next; - clear_buddies(cfs_rq, se); + return se; +} +static struct sched_entity * +pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr) +{ + struct sched_entity *se = __pick_next_entity(cfs_rq, curr); + clear_buddies(cfs_rq, se); return se; } @@ -6565,7 +6574,7 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_ struct sched_entity *se = &curr->se, *pse = &p->se; struct cfs_rq *cfs_rq = task_cfs_rq(curr); int scale = cfs_rq->nr_running >= sched_nr_latency; - int next_buddy_marked = 0; + int wpe, next_buddy_marked = 0; if (unlikely(se == pse)) return; @@ -6612,14 +6621,17 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_ find_matching_se(&se, &pse); update_curr(cfs_rq_of(se)); BUG_ON(!pse); - if (wakeup_preempt_entity(se, pse) == 1) { + wpe = wakeup_preempt_entity(se, pse); + if (wpe >= !(wake_flags & WF_KTHREAD)) { /* * Bias pick_next to pick the sched entity that is * triggering this preemption. */ if (!next_buddy_marked) set_next_buddy(pse); - goto preempt; + + if (wpe == 1) + goto preempt; } return; diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 280a3c735935..2ee86ef51001 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1643,7 +1643,8 @@ static inline int task_on_rq_migrating(struct task_struct *p) */ #define WF_SYNC 0x01 /* Waker goes to sleep after wakeup */ #define WF_FORK 0x02 /* Child wakeup after fork */ -#define WF_MIGRATED 0x4 /* Internal use, task got migrated */ +#define WF_MIGRATED 0x04 /* Internal use, task got migrated */ +#define WF_KTHREAD 0x08 /* * To aid in avoiding the subversion of "niceness" due to uneven distribution
On Thu, Dec 12, 2019 at 11:10:31AM +0100, Peter Zijlstra wrote: > @@ -4156,13 +4159,13 @@ check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr) > if (delta_exec < sysctl_sched_min_granularity) > return; > > - se = __pick_first_entity(cfs_rq); > + se = __pick_next_entity(cfs_rq, NULL); > delta = curr->vruntime - se->vruntime; > > if (delta < 0) > return; What I mean with the below comment is, when this isn't enough, try something like: if (se == cfs_rq->next) ideal_runtime /= 2; to make it yield sooner to 'next' buddies. Sadly, due to the whole cgroup mess, we can't say what actual task is on the end of it (without doing a full hierarchy pick, which is more expensive still). > - if (delta > ideal_runtime) > + if (delta > ideal_runtime) // maybe frob this too ? > resched_curr(rq_of(cfs_rq)); > }
On Thu, Dec 12, 2019 at 11:14:24AM +0100, Peter Zijlstra wrote: > On Thu, Dec 12, 2019 at 11:10:31AM +0100, Peter Zijlstra wrote: > > @@ -4156,13 +4159,13 @@ check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr) > > if (delta_exec < sysctl_sched_min_granularity) > > return; > > > > - se = __pick_first_entity(cfs_rq); > > + se = __pick_next_entity(cfs_rq, NULL); > > delta = curr->vruntime - se->vruntime; > > > > if (delta < 0) > > return; > > What I mean with the below comment is, when this isn't enough, try > something like: > > if (se == cfs_rq->next) > ideal_runtime /= 2; > > to make it yield sooner to 'next' buddies. Sadly, due to the whole > cgroup mess, we can't say what actual task is on the end of it (without > doing a full hierarchy pick, which is more expensive still). Just for giggles, that'd look something like: while (!entity_is_task(se) { cfs_rq = group_cfs_rq(se); se = pick_next_entity(cfs_rq, cfs_rq->curr); } p = task_of(se); if (is_per_cpu_kthread(p)) ideal_runtime /= 2; the core-scheduling patch set includes the right primitive for this I think, pick_task_fair(). > > - if (delta > ideal_runtime) > > + if (delta > ideal_runtime) // maybe frob this too ? > > resched_curr(rq_of(cfs_rq)); > > }
On Thu, 12 Dec 2019 at 11:23, Peter Zijlstra <peterz@infradead.org> wrote: > > On Thu, Dec 12, 2019 at 11:14:24AM +0100, Peter Zijlstra wrote: > > On Thu, Dec 12, 2019 at 11:10:31AM +0100, Peter Zijlstra wrote: > > > @@ -4156,13 +4159,13 @@ check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr) > > > if (delta_exec < sysctl_sched_min_granularity) > > > return; > > > > > > - se = __pick_first_entity(cfs_rq); > > > + se = __pick_next_entity(cfs_rq, NULL); > > > delta = curr->vruntime - se->vruntime; > > > > > > if (delta < 0) > > > return; > > > > What I mean with the below comment is, when this isn't enough, try > > something like: > > > > if (se == cfs_rq->next) > > ideal_runtime /= 2; > > > > to make it yield sooner to 'next' buddies. Sadly, due to the whole > > cgroup mess, we can't say what actual task is on the end of it (without > > doing a full hierarchy pick, which is more expensive still). > > Just for giggles, that'd look something like: > > while (!entity_is_task(se) { > cfs_rq = group_cfs_rq(se); > se = pick_next_entity(cfs_rq, cfs_rq->curr); > } > p = task_of(se); > > if (is_per_cpu_kthread(p)) > ideal_runtime /= 2; > > the core-scheduling patch set includes the right primitive for this I > think, pick_task_fair(). why not only updating wan_gran() which is the only function which uses sysctl_sched_wakeup_granularity ? For per cpu kthread, we could set the gran to sched_min_granularity instead of scaling it with thread's priority so per cpu kthread can still preempt current ask even if sysctl_sched_wakeup_granularity is large > > > > - if (delta > ideal_runtime) > > > + if (delta > ideal_runtime) // maybe frob this too ? > > > resched_curr(rq_of(cfs_rq)); > > > }
On Thu, Dec 12, 2019 at 12:20:01PM +0100, Vincent Guittot wrote: > On Thu, 12 Dec 2019 at 11:23, Peter Zijlstra <peterz@infradead.org> wrote: > > Just for giggles, that'd look something like: > > > > while (!entity_is_task(se) { > > cfs_rq = group_cfs_rq(se); > > se = pick_next_entity(cfs_rq, cfs_rq->curr); > > } > > p = task_of(se); > > > > if (is_per_cpu_kthread(p)) > > ideal_runtime /= 2; > > > > the core-scheduling patch set includes the right primitive for this I > > think, pick_task_fair(). > > why not only updating wan_gran() which is the only function which uses > sysctl_sched_wakeup_granularity ? I don't see how, it works on se, which need not be a task. > For per cpu kthread, we could set the gran to sched_min_granularity > instead of scaling it with thread's priority so per cpu kthread can > still preempt current ask even if sysctl_sched_wakeup_granularity is > large Also, we're not poking at wakeup preemption anymore. That, as explained by Dave, is not the right thing to do. What we want instead is to make tick preemption a little more agressive. And tick based preemption currently purely looks at the leftmost entity for each runqueue we find while iterating current. IE, it might never even see the task we tagged with next. Also, did I say I hates cgroups :-)
* Peter Zijlstra <peterz@infradead.org> [2019-12-12 11:10:31]: > > +static struct sched_entity * > +__pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr); I think we already have __pick_next_entity in kernel/sched/fair.c static struct sched_entity *__pick_next_entity(struct sched_entity *se) { struct rb_node *next = rb_next(&se->run_node); if (!next) return NULL; return rb_entry(next, struct sched_entity, run_node); } I checked in v5.5-rc1, v5.4 and tip/master too. Let me know if you were referring to a different version of code. So I modified the only place its called to the newer __pick_next_entity(cfs_rq, curr); But wanted to verify if that's what you had in mind.
On Thu, Dec 12, 2019 at 08:37:37PM +0530, Srikar Dronamraju wrote: > * Peter Zijlstra <peterz@infradead.org> [2019-12-12 11:10:31]: > > > > > +static struct sched_entity * > > +__pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr); > > I think we already have __pick_next_entity in kernel/sched/fair.c D'oh... yeah, I just wrote stuff, it never actually got near a compiler.
* Peter Zijlstra <peterz@infradead.org> [2019-12-12 11:10:31]: > On Thu, Dec 12, 2019 at 09:46:17AM +1100, Dave Chinner wrote: > > On Wed, Dec 11, 2019 at 11:08:29PM +0530, Srikar Dronamraju wrote: > > Good point, something to maybe try (Srikar?) is making tick preemption > more agressive for such tasks. > > The below extends the previous patch to retain the set_next_buddy() on > wakeup, but does not make the actual preemption more agressive. > > Then it 'fixes' the tick preemption to better align with the actual > scheduler pick (ie. consider the buddy hints). > Just to let you know, I tried the patch, but it doesn't help. The results were identical to the one without the patch. I think its probably because when we allow the task to stay on the runqueue, it will surely lead to load_balance and so we see the active-balance kick in. Peter, Based on what Dave is asking for, would you be okay if we add 1. A delayed_wake_list per runqueue, 2. A new wake_up API to add tasks to this delayed wake_list 3. On schedule, tasks on the delayed_wake_list would be actually woken up.
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 44123b4d14e8..2636002e4a0d 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2542,6 +2542,11 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags) goto out; } +#ifdef CONFIG_SMP + if (is_per_cpu_kthread(p)) + wake_flags |= WF_KTHREAD; +#endif + /* * If we are going to wake up a thread waiting for CONDITION we * need to ensure that CONDITION=1 done by the caller can not be diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 69a81a5709ff..8fe40f83804d 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6716,7 +6716,7 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_ find_matching_se(&se, &pse); update_curr(cfs_rq_of(se)); BUG_ON(!pse); - if (wakeup_preempt_entity(se, pse) == 1) { + if (wakeup_preempt_entity(se, pse) >= !(wake_flags & WF_KTHREAD)) { /* * Bias pick_next to pick the sched entity that is * triggering this preemption. diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index c8870c5bd7df..fcd1ed5af9a3 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1643,7 +1643,8 @@ static inline int task_on_rq_migrating(struct task_struct *p) */ #define WF_SYNC 0x01 /* Waker goes to sleep after wakeup */ #define WF_FORK 0x02 /* Child wakeup after fork */ -#define WF_MIGRATED 0x4 /* Internal use, task got migrated */ +#define WF_MIGRATED 0x04 /* Internal use, task got migrated */ +#define WF_KTHREAD 0x08 /* Per CPU Kthread */ /* * To aid in avoiding the subversion of "niceness" due to uneven distribution
A running task can wake-up a per CPU bound kthread on the same CPU. If the current running task doesn't yield the CPU before the next load balance operation, the scheduler would detect load imbalance and try to balance the load. However this load balance would fail as the waiting task is CPU bound, while the running task cannot be moved by the regular load balancer. Finally the active load balancer would kick in and move the task to a different CPU/Core. Moving the task to a different CPU/core can lead to loss in cache affinity leading to poor performance. This is more prone to happen if the current running task is CPU intensive and the sched_wake_up_granularity is set to larger value. When the sched_wake_up_granularity was relatively small, it was observed that the bound thread would complete before the load balancer would have chosen to move the cache hot task to a different CPU. To deal with this situation, the current running task would yield to a per CPU bound kthread, provided kthread is not CPU intensive. /pboffline/hwcct_prg_old/lib/fsperf -t overwrite --noclean -f 5g -b 4k /pboffline (With sched_wake_up_granularity set to 15ms) Performance counter stats for 'system wide' (5 runs): event v5.4 v5.4 + patch(v3) probe:active_load_balance_cpu_stop 1,919 ( +- 2.89% ) 4 ( +- 20.48% ) sched:sched_waking 441,535 ( +- 0.17% ) 914,630 ( +- 0.18% ) sched:sched_wakeup 441,533 ( +- 0.17% ) 914,630 ( +- 0.18% ) sched:sched_wakeup_new 2,436 ( +- 8.08% ) 545 ( +- 4.02% ) sched:sched_switch 797,007 ( +- 0.26% ) 1,490,261 ( +- 0.10% ) sched:sched_migrate_task 20,998 ( +- 1.04% ) 2,492 ( +- 11.56% ) sched:sched_process_free 2,436 ( +- 7.90% ) 526 ( +- 3.65% ) sched:sched_process_exit 2,451 ( +- 7.85% ) 546 ( +- 4.06% ) sched:sched_wait_task 7 ( +- 21.20% ) 1 ( +- 40.82% ) sched:sched_process_wait 3,951 ( +- 9.14% ) 854 ( +- 5.33% ) sched:sched_process_fork 2,435 ( +- 8.09% ) 545 ( +- 3.96% ) sched:sched_process_exec 1,023 ( +- 12.21% ) 205 ( +- 5.13% ) sched:sched_wake_idle_without_ipi 187,794 ( +- 1.14% ) 353,579 ( +- 0.42% ) Elasped time in seconds 289.43 +- 1.42 ( +- 0.49% ) 72.7318 +- 0.0545 ( +- 0.07% ) Throughput results v5.4 Trigger time:................... 0.842679 s (Throughput: 6075.86 MB/s) Asynchronous submit time:....... 1.0184 s (Throughput: 5027.49 MB/s) Synchronous submit time:........ 0 s (Throughput: 0 MB/s) I/O time:....................... 263.17 s (Throughput: 19.455 MB/s) Ratio trigger time to I/O time:.0.00320202 v5.4 + patch(v3) Trigger time:................... 0.852413 s (Throughput: 6006.47 MB/s) Asynchronous submit time:....... 0.773043 s (Throughput: 6623.17 MB/s) Synchronous submit time:........ 0 s (Throughput: 0 MB/s) I/O time:....................... 44.341 s (Throughput: 115.468 MB/s) Ratio trigger time to I/O time:. 0.019224 (With sched_wake_up_granularity set to 4ms) Performance counter stats for 'system wide' (5 runs): event v5.4 v5.4 + patch(v3) probe:active_load_balance_cpu_stop 6 ( +- 6.03% ) 5 ( +- 15.04% ) sched:sched_waking 899,880 ( +- 0.38% ) 912,625 ( +- 0.41% ) sched:sched_wakeup 899,878 ( +- 0.38% ) 912,624 ( +- 0.41% ) sched:sched_wakeup_new 622 ( +- 11.95% ) 550 ( +- 3.85% ) sched:sched_switch 1,458,214 ( +- 0.40% ) 1,489,032 ( +- 0.41% ) sched:sched_migrate_task 3,120 ( +- 10.00% ) 2,524 ( +- 5.54% ) sched:sched_process_free 608 ( +- 12.18% ) 528 ( +- 3.89% ) sched:sched_process_exit 623 ( +- 11.91% ) 550 ( +- 3.79% ) sched:sched_wait_task 1 ( +- 31.18% ) 1 ( +- 66.67% ) sched:sched_process_wait 998 ( +- 13.22% ) 867 ( +- 4.41% ) sched:sched_process_fork 622 ( +- 11.95% ) 550 ( +- 3.88% ) sched:sched_process_exec 242 ( +- 13.81% ) 208 ( +- 4.57% ) sched:sched_wake_idle_without_ipi 349,165 ( +- 0.35% ) 352,443 ( +- 0.21% ) Elasped time in seconds 72.8560 +- 0.0768 ( +- 0.11% ) 72.5523 +- 0.0725 ( +- 0.10% ) Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> --- Changelog: v1 : http://lore.kernel.org/lkml/20191209165122.GA27229@linux.vnet.ibm.com v2 : http://lore.kernel.org/lkml/20191210054330.GF27253@linux.vnet.ibm.com v3 : http://lore.kernel.org/lkml/20191210172307.GD9139@linux.vnet.ibm.com v1->v2: Pass the the right params to try_to_wake_up as correctly pointed out by Dave Chinner v2->v3: Suggestions from Peter Zijlstra including using vtime over context switch and detect per-cpu-kthread in try_to_wake_up v3->v4: Fixed a compilation failed under !CONFIG_SMP reported by kbuild test robot <lkp@intel.com> as is_per_cpu_kthread is only defined for CONFIG_SMP. kernel/sched/core.c | 5 +++++ kernel/sched/fair.c | 2 +- kernel/sched/sched.h | 3 ++- 3 files changed, 8 insertions(+), 2 deletions(-)