aboutsummaryrefslogtreecommitdiffstats
path: root/kernel/sched/sched.h
Commit message (Collapse)AuthorAgeFilesLines
* Merge branch 'sched-core-for-linus' of ↵Linus Torvalds2016-01-111-50/+18
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull scheduler updates from Ingo Molnar: "The main changes in this cycle were: - tickless load average calculation enhancements (Byungchul Park) - vtime handling enhancements (Frederic Weisbecker) - scalability improvement via properly aligning a key structure field (Jiri Olsa) - various stop_machine() fixes (Oleg Nesterov) - sched/numa enhancement (Rik van Riel) - various fixes and improvements (Andi Kleen, Dietmar Eggemann, Geliang Tang, Hiroshi Shimamoto, Joonwoo Park, Peter Zijlstra, Waiman Long, Wanpeng Li, Yuyang Du)" * 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (32 commits) sched/fair: Fix new task's load avg removed from source CPU in wake_up_new_task() sched/core: Move sched_entity::avg into separate cache line x86/fpu: Properly align size in CHECK_MEMBER_AT_END_OF() macro sched/deadline: Fix the earliest_dl.next logic sched/fair: Disable the task group load_avg update for the root_task_group sched/fair: Move the cache-hot 'load_avg' variable into its own cacheline sched/fair: Avoid redundant idle_cpu() call in update_sg_lb_stats() sched/core: Move the sched_to_prio[] arrays out of line sched/cputime: Convert vtime_seqlock to seqcount sched/cputime: Introduce vtime accounting check for readers sched/cputime: Rename vtime_accounting_enabled() to vtime_accounting_cpu_enabled() sched/cputime: Correctly handle task guest time on housekeepers sched/cputime: Clarify vtime symbols and document them sched/cputime: Remove extra cost in task_cputime() sched/fair: Make it possible to account fair load avg consistently sched/fair: Modify the comment about lock assumptions in migrate_task_rq_fair() stop_machine: Clean up the usage of the preemption counter in cpu_stopper_thread() stop_machine: Shift the 'done != NULL' check from cpu_stop_signal_done() to callers stop_machine: Kill cpu_stop_done->executed stop_machine: Change __stop_cpus() to rely on cpu_stop_queue_work() ...
| * sched/fair: Move the cache-hot 'load_avg' variable into its own cachelineWaiman Long2015-12-041-1/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | If a system with large number of sockets was driven to full utilization, it was found that the clock tick handling occupied a rather significant proportion of CPU time when fair group scheduling and autogroup were enabled. Running a java benchmark on a 16-socket IvyBridge-EX system, the perf profile looked like: 10.52% 0.00% java [kernel.vmlinux] [k] smp_apic_timer_interrupt 9.66% 0.05% java [kernel.vmlinux] [k] hrtimer_interrupt 8.65% 0.03% java [kernel.vmlinux] [k] tick_sched_timer 8.56% 0.00% java [kernel.vmlinux] [k] update_process_times 8.07% 0.03% java [kernel.vmlinux] [k] scheduler_tick 6.91% 1.78% java [kernel.vmlinux] [k] task_tick_fair 5.24% 5.04% java [kernel.vmlinux] [k] update_cfs_shares In particular, the high CPU time consumed by update_cfs_shares() was mostly due to contention on the cacheline that contained the task_group's load_avg statistical counter. This cacheline may also contains variables like shares, cfs_rq & se which are accessed rather frequently during clock tick processing. This patch moves the load_avg variable into another cacheline separated from the other frequently accessed variables. It also creates a cacheline aligned kmemcache for task_group to make sure that all the allocated task_group's are cacheline aligned. By doing so, the perf profile became: 9.44% 0.00% java [kernel.vmlinux] [k] smp_apic_timer_interrupt 8.74% 0.01% java [kernel.vmlinux] [k] hrtimer_interrupt 7.83% 0.03% java [kernel.vmlinux] [k] tick_sched_timer 7.74% 0.00% java [kernel.vmlinux] [k] update_process_times 7.27% 0.03% java [kernel.vmlinux] [k] scheduler_tick 5.94% 1.74% java [kernel.vmlinux] [k] task_tick_fair 4.15% 3.92% java [kernel.vmlinux] [k] update_cfs_shares The %cpu time is still pretty high, but it is better than before. The benchmark results before and after the patch was as follows: Before patch - Max-jOPs: 907533 Critical-jOps: 134877 After patch - Max-jOPs: 916011 Critical-jOps: 142366 Signed-off-by: Waiman Long <Waiman.Long@hpe.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Ben Segall <bsegall@google.com> Cc: Douglas Hatch <doug.hatch@hpe.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Morten Rasmussen <morten.rasmussen@arm.com> Cc: Paul Turner <pjt@google.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Scott J Norton <scott.norton@hpe.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Yuyang Du <yuyang.du@intel.com> Link: http://lkml.kernel.org/r/1449081710-20185-3-git-send-email-Waiman.Long@hpe.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * sched/core: Move the sched_to_prio[] arrays out of lineAndi Kleen2015-12-041-40/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When building a kernel with a gcc 6 snapshot the compiler complains about unused const static variables for prio_to_weight and prio_to_mult for multiple scheduler files (all but core.c and autogroup.c) The way the array is currently declared it will be duplicated in every scheduler file that includes sched.h, which seems rather wasteful. Move the array out of line into core.c. I also added a sched_ prefix to avoid any potential name space collisions. Signed-off-by: Andi Kleen <ak@linux.intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1448859583-3252-1-git-send-email-andi@firstfloor.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * sched/fair: Make it possible to account fair load avg consistentlyByungchul Park2015-12-041-1/+10
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The current code accounts for the time a task was absent from the fair class (per ATTACH_AGE_LOAD). However it does not work correctly when a task got migrated or moved to another cgroup while outside of the fair class. This patch tries to address that by aging on migration. We locklessly read the 'last_update_time' stamp from both the old and new cfs_rq, ages the load upto the old time, and sets it to the new time. These timestamps should in general not be more than 1 tick apart from one another, so there is a definite bound on things. Signed-off-by: Byungchul Park <byungchul.park@lge.com> [ Changelog, a few edits and !SMP build fix ] Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1445616981-29904-2-git-send-email-byungchul.park@lge.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * Merge branch 'sched/urgent' into sched/core, to pick up fixes before ↵Ingo Molnar2015-12-041-0/+3
| |\ | | | | | | | | | | | | | | | applying new changes Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * | sched/fair: Remove empty idle enter and exit functionsDietmar Eggemann2015-11-231-8/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Commit cd126afe838d ("sched/fair: Remove rq's runnable avg") got rid of rq->avg and so there is no need to update it any more when entering or exiting idle. Remove the now empty functions idle_{enter|exit}_fair(). Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Yuyang Du <yuyang.du@intel.com> Link: http://lkml.kernel.org/r/1445342681-17171-1-git-send-email-dietmar.eggemann@arm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | | locking, sched: Introduce smp_cond_acquire() and use itPeter Zijlstra2015-12-041-1/+1
| |/ |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Introduce smp_cond_acquire() which combines a control dependency and a read barrier to form acquire semantics. This primitive has two benefits: - it documents control dependencies, - its typically cheaper than using smp_load_acquire() in a loop. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | sched/core: Better document the try_to_wake_up() barriersPeter Zijlstra2015-12-041-0/+3
|/ | | | | | | | | | | | | | | Explain how the control dependency and smp_rmb() end up providing ACQUIRE semantics and pair with smp_store_release() in finish_lock_switch(). Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched/core: Remove a parameter in the migrate_task_rq() functionxiaofeng.yan2015-10-061-1/+1
| | | | | | | | | | | | | | | | | | The parameter "int next_cpu" in the following function is unused: migrate_task_rq(struct task_struct *p, int next_cpu) Remove it. Signed-off-by: xiaofeng.yan <yanxiaofeng@inspur.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Link: http://lkml.kernel.org/r/1442991360-31945-1-git-send-email-yanxiaofeng@inspur.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched/core: Fix task and run queue sched_info::run_delay inconsistenciesPeter Zijlstra2015-10-061-6/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Mike Meyer reported the following bug: > During evaluation of some performance data, it was discovered thread > and run queue run_delay accounting data was inconsistent with the other > accounting data that was collected. Further investigation found under > certain circumstances execution time was leaking into the task and > run queue accounting of run_delay. > > Consider the following sequence: > > a. thread is running. > b. thread moves beween cgroups, changes scheduling class or priority. > c. thread sleeps OR > d. thread involuntarily gives up cpu. > > a. implies: > > thread->sched_info.last_queued = 0 > > a. and b. results in the following: > > 1. dequeue_task(rq, thread) > > sched_info_dequeued(rq, thread) > delta = 0 > > sched_info_reset_dequeued(thread) > thread->sched_info.last_queued = 0 > > thread->sched_info.run_delay += delta > > 2. enqueue_task(rq, thread) > > sched_info_queued(rq, thread) > > /* thread is still on cpu at this point. */ > thread->sched_info.last_queued = task_rq(thread)->clock; > > c. results in: > > dequeue_task(rq, thread) > > sched_info_dequeued(rq, thread) > > /* delta is execution time not run_delay. */ > delta = task_rq(thread)->clock - thread->sched_info.last_queued > > sched_info_reset_dequeued(thread) > thread->sched_info.last_queued = 0 > > thread->sched_info.run_delay += delta > > Since thread was running between enqueue_task(rq, thread) and > dequeue_task(rq, thread), the delta above is really execution > time and not run_delay. > > d. results in: > > __sched_info_switch(thread, next_thread) > > sched_info_depart(rq, thread) > > sched_info_queued(rq, thread) > > /* last_queued not updated due to being non-zero */ > return > > Since thread was running between enqueue_task(rq, thread) and > __sched_info_switch(thread, next_thread), the execution time > between enqueue_task(rq, thread) and > __sched_info_switch(thread, next_thread) now will become > associated with run_delay due to when last_queued was last updated. > This alternative patch solves the problem by not calling sched_info_{de,}queued() in {de,en}queue_task(). Therefore the sched_info state is preserved and things work as expected. By inlining the {de,en}queue_task() functions the new condition becomes (mostly) a compile-time constant and we'll not emit any new branch instructions. It even shrinks the code (due to inlining {en,de}queue_task()): $ size defconfig-build/kernel/sched/core.o defconfig-build/kernel/sched/core.o.orig text data bss dec hex filename 64019 23378 2344 89741 15e8d defconfig-build/kernel/sched/core.o 64149 23378 2344 89871 15f0f defconfig-build/kernel/sched/core.o.orig Reported-by: Mike Meyer <Mike.Meyer@Teradata.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Link: http://lkml.kernel.org/r/20150930154413.GO3604@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
* Merge branch 'sched/urgent' into sched/core, to pick up fixes before ↵Ingo Molnar2015-10-061-2/+3
|\ | | | | | | | | | | applying new changes Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * sched/core: Fix TASK_DEAD race in finish_task_switch()Peter Zijlstra2015-10-061-2/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | So the problem this patch is trying to address is as follows: CPU0 CPU1 context_switch(A, B) ttwu(A) LOCK A->pi_lock A->on_cpu == 0 finish_task_switch(A) prev_state = A->state <-. WMB | A->on_cpu = 0; | UNLOCK rq0->lock | | context_switch(C, A) `-- A->state = TASK_DEAD prev_state == TASK_DEAD put_task_struct(A) context_switch(A, C) finish_task_switch(A) A->state == TASK_DEAD put_task_struct(A) The argument being that the WMB will allow the load of A->state on CPU0 to cross over and observe CPU1's store of A->state, which will then result in a double-drop and use-after-free. Now the comment states (and this was true once upon a long time ago) that we need to observe A->state while holding rq->lock because that will order us against the wakeup; however the wakeup will not in fact acquire (that) rq->lock; it takes A->pi_lock these days. We can obviously fix this by upgrading the WMB to an MB, but that is expensive, so we'd rather avoid that. The alternative this patch takes is: smp_store_release(&A->on_cpu, 0), which avoids the MB on some archs, but not important ones like ARM. Reported-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: <stable@vger.kernel.org> # v3.1+ Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Cc: manfred@colorfullife.com Cc: will.deacon@arm.com Fixes: e4a52bcb9a18 ("sched: Remove rq->lock from the first half of ttwu()") Link: http://lkml.kernel.org/r/20150929124509.GG3816@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | sched/deadline: Unify dl_time_before() usageJuri Lelli2015-09-231-5/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Move dl_time_before() static definition in include/linux/sched/deadline.h so that it can be used by different parties without being re-defined. Reported-by: Luca Abeni <luca.abeni@unitn.it> Signed-off-by: Juri Lelli <juri.lelli@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1441188096-23021-3-git-send-email-juri.lelli@arm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | sched/core: Make policy-testing consistentHenrik Austad2015-09-181-0/+9
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Most of the policy-tests are done via the <class>_policy() helpers with the notable exception of idle. A new wrapper for valid_policy() has also been added to improve readability in set_load_weight(). This commit does not change the logical behavior of the scheduler core. Signed-off-by: Henrik Austad <henrik@austad.us> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Link: http://lkml.kernel.org/r/1441810841-4756-1-git-send-email-henrik@austad.us Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | sched/fair: Make utilization tracking CPU scale-invariantDietmar Eggemann2015-09-131-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Besides the existing frequency scale-invariance correction factor, apply CPU scale-invariance correction factor to utilization tracking to compensate for any differences in compute capacity. This could be due to micro-architectural differences (i.e. instructions per seconds) between cpus in HMP systems (e.g. big.LITTLE), and/or differences in the current maximum frequency supported by individual cpus in SMP systems. In the existing implementation utilization isn't comparable between cpus as it is relative to the capacity of each individual CPU. Each segment of the sched_avg.util_sum geometric series is now scaled by the CPU performance factor too so the sched_avg.util_avg of each sched entity will be invariant from the particular CPU of the HMP/SMP system on which the sched entity is scheduled. With this patch, the utilization of a CPU stays relative to the max CPU performance of the fastest CPU in the system. In contrast to utilization (sched_avg.util_sum), load (sched_avg.load_sum) should not be scaled by compute capacity. The utilization metric is based on running time which only makes sense when cpus are _not_ fully utilized (utilization cannot go beyond 100% even if more tasks are added), where load is runnable time which isn't limited by the capacity of the CPU and therefore is a better metric for overloaded scenarios. If we run two nice-0 busy loops on two cpus with different compute capacity their load should be similar since their compute demands are the same. We have to assume that the compute demand of any task running on a fully utilized CPU (no spare cycles = 100% utilization) is high and the same no matter of the compute capacity of its current CPU, hence we shouldn't scale load by CPU capacity. Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Signed-off-by: Morten Rasmussen <morten.rasmussen@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/55CE7409.1000700@arm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | sched/fair: Convert arch_scale_cpu_capacity() from weak function to #defineMorten Rasmussen2015-09-131-0/+11
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Bring arch_scale_cpu_capacity() in line with the recent change of its arch_scale_freq_capacity() sibling in commit dfbca41f3479 ("sched: Optimize freq invariant accounting") from weak function to #define to allow inlining of the function. While at it, remove the ARCH_CAPACITY sched_feature as well. With the change to #define there isn't a straightforward way to allow runtime switch between an arch implementation and the default implementation of arch_scale_cpu_capacity() using sched_feature. The default was to use the arch-specific implementation, but only the arm architecture provides one and that is essentially equivalent to the default implementation. Signed-off-by: Morten Rasmussen <morten.rasmussen@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Dietmar Eggemann <Dietmar.Eggemann@arm.com> Cc: Juri Lelli <Juri.Lelli@arm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: daniel.lezcano@linaro.org Cc: mturquette@baylibre.com Cc: pang.xunlei@zte.com.cn Cc: rjw@rjwysocki.net Cc: sgurrappadi@nvidia.com Cc: vincent.guittot@linaro.org Cc: yuyang.du@intel.com Link: http://lkml.kernel.org/r/1439569394-11974-3-git-send-email-morten.rasmussen@arm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | sched/numa: Convert sched_numa_balancing to a static_branchSrikar Dronamraju2015-09-131-5/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Variable sched_numa_balancing toggles numa_balancing feature. Hence moving from a simple read mostly variable to a more apt static_branch. Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Mike Galbraith <efault@gmx.de> Cc: Rik van Riel <riel@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1439310261-16124-1-git-send-email-srikar@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | sched/numa: Disable sched_numa_balancing on UMA systemsSrikar Dronamraju2015-09-131-6/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Commit 2a1ed24 ("sched/numa: Prefer NUMA hotness over cache hotness") sets sched feature NUMA to true. However this can enable NUMA hinting faults on a UMA system. This commit ensures that NUMA hinting faults occur only on a NUMA system by setting/resetting sched_numa_balancing. This commit: - Makes sched_numa_balancing common to CONFIG_SCHED_DEBUG and !CONFIG_SCHED_DEBUG. Earlier it was only in !CONFIG_SCHED_DEBUG. - Checks for sched_numa_balancing instead of sched_feat(NUMA). Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rik van Riel <riel@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1439290813-6683-3-git-send-email-srikar@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | sched/numa: Rename numabalancing_enabled to sched_numa_balancingSrikar Dronamraju2015-09-131-3/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Simple rename of the 'numabalancing_enabled' variable to 'sched_numa_balancing'. No functional changes. Suggested-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rik van Riel <riel@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1439290813-6683-2-git-send-email-srikar@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | sched/core: Remove unused argument from sched_class::task_move_groupPeter Zijlstra2015-09-131-1/+1
|/ | | | | | | | | | | | The previous patches made the second argument go unused, remove it. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Byungchul Park <byungchul.park@lge.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched: Make sched_class::set_cpus_allowed() unconditionalPeter Zijlstra2015-08-121-0/+2
| | | | | | | | | | | | | | | | | | | Give every class a set_cpus_allowed() method, this enables some small optimization in the RT,DL implementation by avoiding a double cpumask_weight() call. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: dedekind1@gmail.com Cc: juri.lelli@arm.com Cc: mgorman@suse.de Cc: riel@redhat.com Cc: rostedt@goodmis.org Link: http://lkml.kernel.org/r/20150515154833.614517487@infradead.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched: Remove finish_arch_switch()Peter Zijlstra2015-08-041-3/+0
| | | | | | | | | | | | One less arch hook.. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched/fair: Provide runnable_load_avg back to cfs_rqYuyang Du2015-08-031-0/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The cfs_rq's load_avg is composed of runnable_load_avg and blocked_load_avg. Before this series, sometimes the runnable_load_avg is used, and sometimes the load_avg is used. Completely replacing all uses of runnable_load_avg with load_avg may be too big a leap, i.e., the blocked_load_avg is concerned to result in overrated load. Therefore, we get runnable_load_avg back. The new cfs_rq's runnable_load_avg is improved to be updated with all of the runnable sched_eneities at the same time, so the one sched_entity updated and the others stale problem is solved. Signed-off-by: Yuyang Du <yuyang.du@intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: arjan@linux.intel.com Cc: bsegall@google.com Cc: dietmar.eggemann@arm.com Cc: fengguang.wu@intel.com Cc: len.brown@intel.com Cc: morten.rasmussen@arm.com Cc: pjt@google.com Cc: rafael.j.wysocki@intel.com Cc: umgwanakikbuti@gmail.com Cc: vincent.guittot@linaro.org Link: http://lkml.kernel.org/r/1436918682-4971-7-git-send-email-yuyang.du@intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched/fair: Init cfs_rq's sched_entity load averageYuyang Du2015-08-031-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | The runnable load and utilization averages of cfs_rq's sched_entity were not initiated. Like done to a task, give new cfs_rq' sched_entity start values to heavy its load in infant time. Signed-off-by: Yuyang Du <yuyang.du@intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: arjan@linux.intel.com Cc: bsegall@google.com Cc: dietmar.eggemann@arm.com Cc: fengguang.wu@intel.com Cc: len.brown@intel.com Cc: morten.rasmussen@arm.com Cc: pjt@google.com Cc: rafael.j.wysocki@intel.com Cc: umgwanakikbuti@gmail.com Cc: vincent.guittot@linaro.org Link: http://lkml.kernel.org/r/1436918682-4971-5-git-send-email-yuyang.du@intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched/fair: Rewrite runnable load and utilization average trackingYuyang Du2015-08-031-19/+9
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The idea of runnable load average (let runnable time contribute to weight) was proposed by Paul Turner and Ben Segall, and it is still followed by this rewrite. This rewrite aims to solve the following issues: 1. cfs_rq's load average (namely runnable_load_avg and blocked_load_avg) is updated at the granularity of an entity at a time, which results in the cfs_rq's load average is stale or partially updated: at any time, only one entity is up to date, all other entities are effectively lagging behind. This is undesirable. To illustrate, if we have n runnable entities in the cfs_rq, as time elapses, they certainly become outdated: t0: cfs_rq { e1_old, e2_old, ..., en_old } and when we update: t1: update e1, then we have cfs_rq { e1_new, e2_old, ..., en_old } t2: update e2, then we have cfs_rq { e1_old, e2_new, ..., en_old } ... We solve this by combining all runnable entities' load averages together in cfs_rq's avg, and update the cfs_rq's avg as a whole. This is based on the fact that if we regard the update as a function, then: w * update(e) = update(w * e) and update(e1) + update(e2) = update(e1 + e2), then w1 * update(e1) + w2 * update(e2) = update(w1 * e1 + w2 * e2) therefore, by this rewrite, we have an entirely updated cfs_rq at the time we update it: t1: update cfs_rq { e1_new, e2_new, ..., en_new } t2: update cfs_rq { e1_new, e2_new, ..., en_new } ... 2. cfs_rq's load average is different between top rq->cfs_rq and other task_group's per CPU cfs_rqs in whether or not blocked_load_average contributes to the load. The basic idea behind runnable load average (the same for utilization) is that the blocked state is taken into account as opposed to only accounting for the currently runnable state. Therefore, the average should include both the runnable/running and blocked load averages. This rewrite does that. In addition, we also combine runnable/running and blocked averages of all entities into the cfs_rq's average, and update it together at once. This is based on the fact that: update(runnable) + update(blocked) = update(runnable + blocked) This significantly reduces the code as we don't need to separately maintain/update runnable/running load and blocked load. 3. How task_group entities' share is calculated is complex and imprecise. We reduce the complexity in this rewrite to allow a very simple rule: the task_group's load_avg is aggregated from its per CPU cfs_rqs's load_avgs. Then group entity's weight is simply proportional to its own cfs_rq's load_avg / task_group's load_avg. To illustrate, if a task_group has { cfs_rq1, cfs_rq2, ..., cfs_rqn }, then, task_group_avg = cfs_rq1_avg + cfs_rq2_avg + ... + cfs_rqn_avg, then cfs_rqx's entity's share = cfs_rqx_avg / task_group_avg * task_group's share To sum up, this rewrite in principle is equivalent to the current one, but fixes the issues described above. Turns out, it significantly reduces the code complexity and hence increases clarity and efficiency. In addition, the new averages are more smooth/continuous (no spurious spikes and valleys) and updated more consistently and quickly to reflect the load dynamics. As a result, we have less load tracking overhead, better performance, and especially better power efficiency due to more balanced load. Signed-off-by: Yuyang Du <yuyang.du@intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: arjan@linux.intel.com Cc: bsegall@google.com Cc: dietmar.eggemann@arm.com Cc: fengguang.wu@intel.com Cc: len.brown@intel.com Cc: morten.rasmussen@arm.com Cc: pjt@google.com Cc: rafael.j.wysocki@intel.com Cc: umgwanakikbuti@gmail.com Cc: vincent.guittot@linaro.org Link: http://lkml.kernel.org/r/1436918682-4971-3-git-send-email-yuyang.du@intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched/fair: Remove rq's runnable avgYuyang Du2015-08-031-2/+0
| | | | | | | | | | | | | | | | | | | | | | | | | The current rq->avg is not used at all since its merge into the kernel, and the code is in the scheduler's hot path, so remove it. Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Signed-off-by: Yuyang Du <yuyang.du@intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: arjan@linux.intel.com Cc: bsegall@google.com Cc: fengguang.wu@intel.com Cc: len.brown@intel.com Cc: morten.rasmussen@arm.com Cc: pjt@google.com Cc: rafael.j.wysocki@intel.com Cc: umgwanakikbuti@gmail.com Cc: vincent.guittot@linaro.org Link: http://lkml.kernel.org/r/1436918682-4971-2-git-send-email-yuyang.du@intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* Merge branch 'sched-urgent-for-linus' of ↵Linus Torvalds2015-07-041-0/+13
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull scheduler fixes from Ingo Molnar: "Debug info and other statistics fixes and related enhancements" * 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: sched/numa: Fix numa balancing stats in /proc/pid/sched sched/numa: Show numa_group ID in /proc/sched_debug task listings sched/debug: Move print_cfs_rq() declaration to kernel/sched/sched.h sched/stat: Expose /proc/pid/schedstat if CONFIG_SCHED_INFO=y sched/stat: Simplify the sched_info accounting dependency
| * sched/numa: Fix numa balancing stats in /proc/pid/schedSrikar Dronamraju2015-07-041-1/+9
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Commit 44dba3d5d6a1 ("sched: Refactor task_struct to use numa_faults instead of numa_* pointers") modified the way tsk->numa_faults stats are accounted. However that commit never touched show_numa_stats() that is displayed in /proc/pid/sched and thus the numbers displayed in /proc/pid/sched don't match the actual numbers. Fix it by making sure that /proc/pid/sched reflects the task fault numbers. Also add group fault stats too. Also couple of more modifications are added here: 1. Format changes: - Previously we would list two entries per node, one for private and one for shared. Also the home node info was listed in each entry. - Now preferred node, total_faults and current node are displayed separately. - Now there is one entry per node, that lists private,shared task and group faults. 2. Unit changes: - p->numa_pages_migrated was getting reset after every read of /proc/pid/sched. It's more useful to have absolute numbers since differential migrations between two accesses can be more easily calculated. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Acked-by: Rik van Riel <riel@redhat.com> Cc: Iulia Manda <iulia.manda21@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1435252903-1081-4-git-send-email-srikar@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * sched/debug: Move print_cfs_rq() declaration to kernel/sched/sched.hSrikar Dronamraju2015-07-041-0/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently print_cfs_rq() is declared in include/linux/sched.h. However it's not used outside kernel/sched. Hence move the declaration to kernel/sched/sched.h Also some functions are only available for CONFIG_SCHED_DEBUG=y. Hence move the declarations to within the #ifdef. Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Acked-by: Rik van Riel <riel@redhat.com> Cc: Iulia Manda <iulia.manda21@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1435252903-1081-2-git-send-email-srikar@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | Merge branch 'sched-hrtimers-for-linus' of ↵Linus Torvalds2015-06-241-4/+25
|\ \ | |/ |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull scheduler updates from Thomas Gleixner: "This series of scheduler updates depends on sched/core and timers/core branches, which are already in your tree: - Scheduler balancing overhaul to plug a hard to trigger race which causes an oops in the balancer (Peter Zijlstra) - Lockdep updates which are related to the balancing updates (Peter Zijlstra)" * 'sched-hrtimers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: sched,lockdep: Employ lock pinning lockdep: Implement lock pinning lockdep: Simplify lock_release() sched: Streamline the task migration locking a little sched: Move code around sched,dl: Fix sched class hopping CBS hole sched, dl: Convert switched_{from, to}_dl() / prio_changed_dl() to balance callbacks sched,dl: Remove return value from pull_dl_task() sched, rt: Convert switched_{from, to}_rt() / prio_changed_rt() to balance callbacks sched,rt: Remove return value from pull_rt_task() sched: Allow balance callbacks for check_class_changed() sched: Use replace normalize_task() with __sched_setscheduler() sched: Replace post_schedule with a balance callback list
| * sched,lockdep: Employ lock pinningPeter Zijlstra2015-06-191-2/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Employ the new lockdep lock pinning annotation to ensure no 'accidental' lock-breaks happen with rq->lock. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: ktkhai@parallels.com Cc: rostedt@goodmis.org Cc: juri.lelli@gmail.com Cc: pang.xunlei@linaro.org Cc: oleg@redhat.com Cc: wanpeng.li@linux.intel.com Cc: umgwanakikbuti@gmail.com Link: http://lkml.kernel.org/r/20150611124744.003233193@infradead.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| * sched: Replace post_schedule with a balance callback listPeter Zijlstra2015-06-191-2/+17
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Generalize the post_schedule() stuff into a balance callback list. This allows us to more easily use it outside of schedule() and cross sched_class. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: ktkhai@parallels.com Cc: rostedt@goodmis.org Cc: juri.lelli@gmail.com Cc: pang.xunlei@linaro.org Cc: oleg@redhat.com Cc: wanpeng.li@linux.intel.com Cc: umgwanakikbuti@gmail.com Link: http://lkml.kernel.org/r/20150611124742.424032725@infradead.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| * Merge branch 'timers/core' into sched/hrtimersThomas Gleixner2015-06-191-4/+3
| |\ | | | | | | | | | | | | Merge sched/core and timers/core so we can apply the sched balancing patch queue, which depends on both.
* | \ Merge branch 'timers-core-for-linus' of ↵Linus Torvalds2015-06-221-4/+3
|\ \ \ | | |/ | |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull timer updates from Thomas Gleixner: "A rather largish update for everything time and timer related: - Cache footprint optimizations for both hrtimers and timer wheel - Lower the NOHZ impact on systems which have NOHZ or timer migration disabled at runtime. - Optimize run time overhead of hrtimer interrupt by making the clock offset updates smarter - hrtimer cleanups and removal of restrictions to tackle some problems in sched/perf - Some more leap second tweaks - Another round of changes addressing the 2038 problem - First step to change the internals of clock event devices by introducing the necessary infrastructure - Allow constant folding for usecs/msecs_to_jiffies() - The usual pile of clockevent/clocksource driver updates The hrtimer changes contain updates to sched, perf and x86 as they depend on them plus changes all over the tree to cleanup API changes and redundant code, which got copied all over the place. The y2038 changes touch s390 to remove the last non 2038 safe code related to boot/persistant clock" * 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (114 commits) clocksource: Increase dependencies of timer-stm32 to limit build wreckage timer: Minimize nohz off overhead timer: Reduce timer migration overhead if disabled timer: Stats: Simplify the flags handling timer: Replace timer base by a cpu index timer: Use hlist for the timer wheel hash buckets timer: Remove FIFO "guarantee" timers: Sanitize catchup_timer_jiffies() usage hrtimer: Allow hrtimer::function() to free the timer seqcount: Introduce raw_write_seqcount_barrier() seqcount: Rename write_seqcount_barrier() hrtimer: Fix hrtimer_is_queued() hole hrtimer: Remove HRTIMER_STATE_MIGRATE selftest: Timers: Avoid signal deadlock in leap-a-day timekeeping: Copy the shadow-timekeeper over the real timekeeper last clockevents: Check state instead of mode in suspend/resume path selftests: timers: Add leap-second timer edge testing to leap-a-day.c ntp: Do leapsecond adjustment in adjtimex read path time: Prevent early expiry of hrtimers[CLOCK_REALTIME] at the leap second edge ntp: Introduce and use SECS_PER_DAY macro instead of 86400 ...
| * | sched,perf: Fix periodic timersPeter Zijlstra2015-05-181-3/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | In the below two commits (see Fixes) we have periodic timers that can stop themselves when they're no longer required, but need to be (re)-started when their idle condition changes. Further complications is that we want the timer handler to always do the forward such that it will always correctly deal with the overruns, and we do not want to race such that the handler has already decided to stop, but the (external) restart sees the timer still active and we end up with a 'lost' timer. The problem with the current code is that the re-start can come before the callback does the forward, at which point the forward from the callback will WARN about forwarding an enqueued timer. Now, conceptually its easy to detect if you're before or after the fwd by comparing the expiration time against the current time. Of course, that's expensive (and racy) because we don't have the current time. Alternatively one could cache this state inside the timer, but then everybody pays the overhead of maintaining this extra state, and that is undesired. The only other option that I could see is the external timer_active variable, which I tried to kill before. I would love a nicer interface for this seemingly simple 'problem' but alas. Fixes: 272325c4821f ("perf: Fix mux_interval hrtimer wreckage") Fixes: 77a4d1a1b9a1 ("sched: Cleanup bandwidth timers") Cc: pjt@google.com Cc: tglx@linutronix.de Cc: klamm@yandex-team.ru Cc: mingo@kernel.org Cc: bsegall@google.com Cc: hpa@zytor.com Cc: Sasha Levin <sasha.levin@oracle.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: http://lkml.kernel.org/r/20150514102311.GX21418@twins.programming.kicks-ass.net
| * | sched: Cleanup bandwidth timersPeter Zijlstra2015-04-221-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Roman reported a 3 cpu lockup scenario involving __start_cfs_bandwidth(). The more I look at that code the more I'm convinced its crack, that entire __start_cfs_bandwidth() thing is brain melting, we don't need to cancel a timer before starting it, *hrtimer_start*() will happily remove the timer for you if its still enqueued. Removing that, removes a big part of the problem, no more ugly cancel loop to get stuck in. So now, if I understand things right, the entire reason you have this cfs_b->lock guarded ->timer_active nonsense is to make sure we don't accidentally lose the timer. It appears to me that it should be possible to guarantee that same by unconditionally (re)starting the timer when !queued. Because regardless what hrtimer::function will return, if we beat it to (re)enqueue the timer, it doesn't matter. Now, because hrtimers don't come with any serialization guarantees we must ensure both handler and (re)start loop serialize their access to the hrtimer to avoid both trying to forward the timer at the same time. Update the rt bandwidth timer to match. This effectively reverts: 09dc4ab03936 ("sched/fair: Fix tg_set_cfs_bandwidth() deadlock on rq->lock"). Reported-by: Roman Gushchin <klamm@yandex-team.ru> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Ben Segall <bsegall@google.com> Cc: Paul Turner <pjt@google.com> Link: http://lkml.kernel.org/r/20150415095011.804589208@infradead.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
* | | sched/deadline: Drop duplicate init_sched_dl_class() declarationWanpeng Li2015-06-191-1/+0
| |/ |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | There are two init_sched_dl_class() declarations, this patch drops the duplicate. Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Borislav Petkov <bp@alien8.de> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Juri Lelli <juri.lelli@arm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1431496867-4194-5-git-send-email-wanpeng.li@linux.intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | sched, timer: Convert usages of ACCESS_ONCE() in the scheduler to ↵Jason Low2015-05-081-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | READ_ONCE()/WRITE_ONCE() ACCESS_ONCE doesn't work reliably on non-scalar types. This patch removes the rest of the existing usages of ACCESS_ONCE() in the scheduler, and use the new READ_ONCE() and WRITE_ONCE() APIs as appropriate. Signed-off-by: Jason Low <jason.low2@hp.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Rik van Riel <riel@redhat.com> Acked-by: Waiman Long <Waiman.Long@hp.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Aswin Chandramouleeswaran <aswin@hp.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Mike Galbraith <umgwanakikbuti@gmail.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Preeti U Murthy <preeti@linux.vnet.ibm.com> Cc: Scott J Norton <scott.norton@hp.com> Cc: Steven Rostedt <rostedt@goodmis.org> Link: http://lkml.kernel.org/r/1430251224-5764-2-git-send-email-jason.low2@hp.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | sched: Move the loadavg code to a more obvious locationPeter Zijlstra2015-05-081-2/+6
|/ | | | | | | | | | | | | | | | | | I could not find the loadavg code.. turns out it was hidden in a file called proc.c. It further got mingled up with the cruft per rq load indexes (which we really want to get rid of). Move the per rq load indexes into the fair.c load-balance code (that's the only thing that uses them) and rename proc.c to loadavg.c so we can find it again. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Borislav Petkov <bp@alien8.de> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Thomas Gleixner <tglx@linutronix.de> [ Did minor cleanups to the code. ] Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched/core: Remove unused argument from init_[rt|dl]_rq()Abel Vesa2015-04-021-2/+2
| | | | | | | | | | Obviously, 'rq' is not used in these two functions, therefore, there is no reason for it to be passed as an argument. Signed-off-by: Abel Vesa <abelvesa@gmail.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: http://lkml.kernel.org/r/1425383427-26244-1-git-send-email-abelvesa@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched: Optimize freq invariant accountingPeter Zijlstra2015-03-271-1/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently the freq invariant accounting (in __update_entity_runnable_avg() and sched_rt_avg_update()) get the scale factor from a weak function call, this means that even for archs that default on their implementation the compiler cannot see into this function and optimize the extra scaling math away. This is sad, esp. since its a 64-bit multiplication which can be quite costly on some platforms. So replace the weak function with #ifdef and __always_inline goo. This is not quite as nice from an arch support PoV but should at least result in compile time errors if done wrong. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Ben Segall <bsegall@google.com> Cc: Morten.Rasmussen@arm.com Cc: Paul Turner <pjt@google.com> Cc: Vincent Guittot <vincent.guittot@linaro.org> Cc: dietmar.eggemann@arm.com Cc: efault@gmx.de Cc: kamalesh@linux.vnet.ibm.com Cc: nicolas.pitre@linaro.org Cc: preeti@linux.vnet.ibm.com Cc: riel@redhat.com Link: http://lkml.kernel.org/r/20150323131905.GF23123@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched: Remove unused struct sched_group_capacity::capacity_origVincent Guittot2015-03-271-1/+1
| | | | | | | | | | | | | | | | | | The 'struct sched_group_capacity::capacity_orig' field is no longer used in the scheduler so we can remove it. Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Morten.Rasmussen@arm.com Cc: dietmar.eggemann@arm.com Cc: efault@gmx.de Cc: kamalesh@linux.vnet.ibm.com Cc: linaro-kernel@lists.linaro.org Cc: nicolas.pitre@linaro.org Cc: preeti@linux.vnet.ibm.com Cc: riel@redhat.com Link: http://lkml.kernel.org/r/1425378903-5349-1-git-send-email-vincent.guittot@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched: Add struct rq::cpu_capacity_origVincent Guittot2015-03-271-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | This new field 'cpu_capacity_orig' reflects the original capacity of a CPU before being altered by rt tasks and/or IRQ The cpu_capacity_orig will be used: - to detect when the capacity of a CPU has been noticeably reduced so we can trig load balance to look for a CPU with better capacity. As an example, we can detect when a CPU handles a significant amount of irq (with CONFIG_IRQ_TIME_ACCOUNTING) but this CPU is seen as an idle CPU by scheduler whereas CPUs, which are really idle, are available. - evaluate the available capacity for CFS tasks Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com> Acked-by: Morten Rasmussen <morten.rasmussen@arm.com> Cc: Morten.Rasmussen@arm.com Cc: dietmar.eggemann@arm.com Cc: efault@gmx.de Cc: linaro-kernel@lists.linaro.org Cc: nicolas.pitre@linaro.org Cc: preeti@linux.vnet.ibm.com Cc: riel@redhat.com Link: http://lkml.kernel.org/r/1425052454-25797-7-git-send-email-vincent.guittot@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched: Make scale_rt invariant with frequencyVincent Guittot2015-03-271-1/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The average running time of RT tasks is used to estimate the remaining compute capacity for CFS tasks. This remaining capacity is the original capacity scaled down by a factor (aka scale_rt_capacity). This estimation of available capacity must also be invariant with frequency scaling. A frequency scaling factor is applied on the running time of the RT tasks for computing scale_rt_capacity. In sched_rt_avg_update(), we now scale the RT execution time like below: rq->rt_avg += rt_delta * arch_scale_freq_capacity() >> SCHED_CAPACITY_SHIFT Then, scale_rt_capacity can be summarized by: scale_rt_capacity = SCHED_CAPACITY_SCALE * available / total with available = total - rq->rt_avg This has been been optimized in current code by: scale_rt_capacity = available / (total >> SCHED_CAPACITY_SHIFT) But we can also developed the equation like below: scale_rt_capacity = SCHED_CAPACITY_SCALE - ((rq->rt_avg << SCHED_CAPACITY_SHIFT) / total) and we can optimize the equation by removing SCHED_CAPACITY_SHIFT shift in the computation of rq->rt_avg and scale_rt_capacity(). so rq->rt_avg += rt_delta * arch_scale_freq_capacity() and scale_rt_capacity = SCHED_CAPACITY_SCALE - (rq->rt_avg / total) arch_scale_frequency_capacity() will be called in the hot path of the scheduler which implies to have a short and efficient function. As an example, arch_scale_frequency_capacity() should return a cached value that is updated periodically outside of the hot path. Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Morten Rasmussen <morten.rasmussen@arm.com> Cc: Morten.Rasmussen@arm.com Cc: dietmar.eggemann@arm.com Cc: efault@gmx.de Cc: kamalesh@linux.vnet.ibm.com Cc: linaro-kernel@lists.linaro.org Cc: nicolas.pitre@linaro.org Cc: preeti@linux.vnet.ibm.com Cc: riel@redhat.com Link: http://lkml.kernel.org/r/1425052454-25797-6-git-send-email-vincent.guittot@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched: Add sched_avg::utilization_avg_contribVincent Guittot2015-03-271-1/+7
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Add new statistics which reflect the average time a task is running on the CPU and the sum of these running time of the tasks on a runqueue. The latter is named utilization_load_avg. This patch is based on the usage metric that was proposed in the 1st versions of the per-entity load tracking patchset by Paul Turner <pjt@google.com> but that has be removed afterwards. This version differs from the original one in the sense that it's not linked to task_group. The rq's utilization_load_avg will be used to check if a rq is overloaded or not instead of trying to compute how many tasks a group of CPUs can handle. Rename runnable_avg_period into avg_period as it is now used with both runnable_avg_sum and running_avg_sum. Add some descriptions of the variables to explain their differences. Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Morten Rasmussen <morten.rasmussen@arm.com> Cc: Paul Turner <pjt@google.com> Cc: Ben Segall <bsegall@google.com> Cc: Ben Segall <bsegall@google.com> Cc: Morten.Rasmussen@arm.com Cc: Paul Turner <pjt@google.com> Cc: dietmar.eggemann@arm.com Cc: efault@gmx.de Cc: kamalesh@linux.vnet.ibm.com Cc: linaro-kernel@lists.linaro.org Cc: nicolas.pitre@linaro.org Cc: preeti@linux.vnet.ibm.com Cc: riel@redhat.com Link: http://lkml.kernel.org/r/1425052454-25797-2-git-send-email-vincent.guittot@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched/rt: Use IPI to trigger RT task push migration instead of pullingSteven Rostedt2015-03-231-0/+12
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When debugging the latencies on a 40 core box, where we hit 300 to 500 microsecond latencies, I found there was a huge contention on the runqueue locks. Investigating it further, running ftrace, I found that it was due to the pulling of RT tasks. The test that was run was the following: cyclictest --numa -p95 -m -d0 -i100 This created a thread on each CPU, that would set its wakeup in iterations of 100 microseconds. The -d0 means that all the threads had the same interval (100us). Each thread sleeps for 100us and wakes up and measures its latencies. cyclictest is maintained at: git://git.kernel.org/pub/scm/linux/kernel/git/clrkwllms/rt-tests.git What happened was another RT task would be scheduled on one of the CPUs that was running our test, when the other CPU tests went to sleep and scheduled idle. This caused the "pull" operation to execute on all these CPUs. Each one of these saw the RT task that was overloaded on the CPU of the test that was still running, and each one tried to grab that task in a thundering herd way. To grab the task, each thread would do a double rq lock grab, grabbing its own lock as well as the rq of the overloaded CPU. As the sched domains on this box was rather flat for its size, I saw up to 12 CPUs block on this lock at once. This caused a ripple affect with the rq locks especially since the taking was done via a double rq lock, which means that several of the CPUs had their own rq locks held while trying to take this rq lock. As these locks were blocked, any wakeups or load balanceing on these CPUs would also block on these locks, and the wait time escalated. I've tried various methods to lessen the load, but things like an atomic counter to only let one CPU grab the task wont work, because the task may have a limited affinity, and we may pick the wrong CPU to take that lock and do the pull, to only find out that the CPU we picked isn't in the task's affinity. Instead of doing the PULL, I now have the CPUs that want the pull to send over an IPI to the overloaded CPU, and let that CPU pick what CPU to push the task to. No more need to grab the rq lock, and the push/pull algorithm still works fine. With this patch, the latency dropped to just 150us over a 20 hour run. Without the patch, the huge latencies would trigger in seconds. I've created a new sched feature called RT_PUSH_IPI, which is enabled by default. When RT_PUSH_IPI is not enabled, the old method of grabbing the rq locks and having the pulling CPU do the work is implemented. When RT_PUSH_IPI is enabled, the IPI is sent to the overloaded CPU to do a push. To enabled or disable this at run time: # mount -t debugfs nodev /sys/kernel/debug # echo RT_PUSH_IPI > /sys/kernel/debug/sched_features or # echo NO_RT_PUSH_IPI > /sys/kernel/debug/sched_features Update: This original patch would send an IPI to all CPUs in the RT overload list. But that could theoretically cause the reverse issue. That is, there could be lots of overloaded RT queues and one CPU lowers its priority. It would then send an IPI to all the overloaded RT queues and they could then all try to grab the rq lock of the CPU lowering its priority, and then we have the same problem. The latest design sends out only one IPI to the first overloaded CPU. It tries to push any tasks that it can, and then looks for the next overloaded CPU that can push to the source CPU. The IPIs stop when all overloaded CPUs that have pushable tasks that have priorities greater than the source CPU are covered. In case the source CPU lowers its priority again, a flag is set to tell the IPI traversal to restart with the first RT overloaded CPU after the source CPU. Parts-suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Joern Engel <joern@purestorage.com> Cc: Clark Williams <williams@redhat.com> Cc: Mike Galbraith <umgwanakikbuti@gmail.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20150318144946.2f3cc982@gandalf.local.home Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched: Make dl_task_time() use task_rq_lock()Peter Zijlstra2015-02-181-0/+76
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Kirill reported that a dl task can be throttled and dequeued at the same time. This happens, when it becomes throttled in schedule(), which is called to go to sleep: current->state = TASK_INTERRUPTIBLE; schedule() deactivate_task() dequeue_task_dl() update_curr_dl() start_dl_timer() __dequeue_task_dl() prev->on_rq = 0; This invalidates the assumption from commit 0f397f2c90ce ("sched/dl: Fix race in dl_task_timer()"): "The only reason we don't strictly need ->pi_lock now is because we're guaranteed to have p->state == TASK_RUNNING here and are thus free of ttwu races". And therefore we have to use the full task_rq_lock() here. This further amends the fact that we forgot to update the rq lock loop for TASK_ON_RQ_MIGRATE, from commit cca26e8009d1 ("sched: Teach scheduler to understand TASK_ON_RQ_MIGRATING state"). Reported-by: Kirill Tkhai <ktkhai@parallels.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Juri Lelli <juri.lelli@arm.com> Link: http://lkml.kernel.org/r/20150217123139.GN5029@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched/core: Rework rq->clock update skipsPeter Zijlstra2015-01-141-2/+13
| | | | | | | | | | | | | | | | | | | | The original purpose of rq::skip_clock_update was to avoid 'costly' clock updates for back to back wakeup-preempt pairs. The big problem with it has always been that the rq variable is unaware of the context and causes indiscrimiate clock skips. Rework the entire thing and create a sense of context by only allowing schedule() to skip clock updates. (XXX can we measure the cost of the added store?) By ensuring only schedule can ever skip an update, we guarantee we're never more than 1 tick behind on the update. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: umgwanakikbuti@gmail.com Link: http://lkml.kernel.org/r/20150105103554.432381549@infradead.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched/core: Validate rq_clock*() serializationPeter Zijlstra2015-01-141-0/+7
| | | | | | | | | | | | | | | | rq->clock{,_task} are serialized by rq->lock, verify this. One immediate fail is the usage in scale_rt_capability, so 'annotate' that for now, there's more 'funny' there. Maybe change rq->lock into a raw_seqlock_t? (Only 32-bit is affected) Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: http://lkml.kernel.org/r/20150105103554.361872747@infradead.org Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: umgwanakikbuti@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* Merge branch 'sched/urgent' into sched/core, to pick up fixes before ↵Ingo Molnar2014-11-161-0/+2
|\ | | | | | | | | | | applying more changes Signed-off-by: Ingo Molnar <mingo@kernel.org>
generated by cgit (git 2.34.1) at 2025-03-04 00:52:28 +0000