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2015-05-08sched/core: Fix regression in cpuset_cpu_inactive() for suspendOmar Sandoval
Commit 3c18d447b3b3 ("sched/core: Check for available DL bandwidth in cpuset_cpu_inactive()"), a SCHED_DEADLINE bugfix, had a logic error that caused a regression in setting a CPU inactive during suspend. I ran into this when a program was failing pthread_setaffinity_np() with EINVAL after a suspend+wake up. A simple reproducer: $ ./a.out sched_setaffinity: Success $ systemctl suspend $ ./a.out sched_setaffinity: Invalid argument ... where ./a.out is: #define _GNU_SOURCE #include <errno.h> #include <sched.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> int main(void) { long num_cores; cpu_set_t cpu_set; int ret; num_cores = sysconf(_SC_NPROCESSORS_ONLN); CPU_ZERO(&cpu_set); CPU_SET(num_cores - 1, &cpu_set); errno = 0; ret = sched_setaffinity(getpid(), sizeof(cpu_set), &cpu_set); perror("sched_setaffinity"); return ret ? EXIT_FAILURE : EXIT_SUCCESS; } The mistake is that suspend is handled in the action == CPU_DOWN_PREPARE_FROZEN case of the switch statement in cpuset_cpu_inactive(). However, the commit in question masked out CPU_TASKS_FROZEN from the action, making this case dead. The fix is straightforward. Signed-off-by: Omar Sandoval <osandov@osandov.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Borislav Petkov <bp@alien8.de> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Juri Lelli <juri.lelli@arm.com> Cc: Thomas Gleixner <tglx@linutronix.de> Fixes: 3c18d447b3b3 ("sched/core: Check for available DL bandwidth in cpuset_cpu_inactive()") Link: http://lkml.kernel.org/r/1cb5ecb3d6543c38cce5790387f336f54ec8e2bc.1430733960.git.osandov@osandov.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-05-08sched: Handle priority boosted tasks proper in setscheduler()Thomas Gleixner
Ronny reported that the following scenario is not handled correctly: T1 (prio = 10) lock(rtmutex); T2 (prio = 20) lock(rtmutex) boost T1 T1 (prio = 20) sys_set_scheduler(prio = 30) T1 prio = 30 .... sys_set_scheduler(prio = 10) T1 prio = 30 The last step is wrong as T1 should now be back at prio 20. Commit c365c292d059 ("sched: Consider pi boosting in setscheduler()") only handles the case where a boosted tasks tries to lower its priority. Fix it by taking the new effective priority into account for the decision whether a change of the priority is required. Reported-by: Ronny Meeus <ronny.meeus@gmail.com> Tested-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Steven Rostedt <rostedt@goodmis.org> Cc: <stable@vger.kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Mike Galbraith <umgwanakikbuti@gmail.com> Fixes: c365c292d059 ("sched: Consider pi boosting in setscheduler()") Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1505051806060.4225@nanos Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-04-30Merge tag 'pm+acpi-4.1-rc2' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm Pull power management and ACPI fixes from Rafael Wysocki: "Three regression fixes this time, one for a recent regression in the cpuidle core affecting multiple systems, one for an inadvertently added duplicate typedef in ACPICA that breaks compilation with GCC 4.5 and one for an ACPI Smart Battery Subsystem driver regression introduced during the 3.18 cycle (stable-candidate). Specifics: - Fix for a regression in the cpuidle core introduced by one of the recent commits in the clockevents_notify() removal series that put a call to a function which had to be executed with disabled interrupts into a code path running with enabled interrupts (Rafael J Wysocki) - Fix for a build problem in ACPICA (with GCC 4.5) introduced by one of the recent ACPICA tools commits that added a duplicate typedef to one of the ACPICA's header files by mistake (Olaf Hering) - Fix for a regression in the ACPI SBS (Smart Battery Subsystem) driver introduced during the 3.18 development cycle causing the smart battery manager to be marked as not present when it should be marked as present (Chris Bainbridge)" * tag 'pm+acpi-4.1-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm: cpuidle: Run tick_broadcast_exit() with disabled interrupts ACPI / SBS: Enable battery manager when present ACPICA: remove duplicate u8 typedef
2015-04-29cpuidle: Run tick_broadcast_exit() with disabled interruptsRafael J. Wysocki
Commit 335f49196fd6 (sched/idle: Use explicit broadcast oneshot control function) replaced clockevents_notify() invocations in cpuidle_idle_call() with direct calls to tick_broadcast_enter() and tick_broadcast_exit(), but it overlooked the fact that interrupts were already enabled before calling the latter which led to functional breakage on systems using idle states with the CPUIDLE_FLAG_TIMER_STOP flag set. Fix that by moving the invocations of tick_broadcast_enter() and tick_broadcast_exit() down into cpuidle_enter_state() where interrupts are still disabled when tick_broadcast_exit() is called. Also ensure that interrupts will be disabled before running tick_broadcast_exit() even if they have been enabled by the idle state's ->enter callback. Trigger a WARN_ON_ONCE() in that case, as we generally don't want that to happen for states with CPUIDLE_FLAG_TIMER_STOP set. Fixes: 335f49196fd6 (sched/idle: Use explicit broadcast oneshot control function) Reported-and-tested-by: Linus Walleij <linus.walleij@linaro.org> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org> Reported-and-tested-by: Sudeep Holla <sudeep.holla@arm.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2015-04-27x86: pvclock: Really remove the sched notifier for cross-cpu migrationsPaolo Bonzini
This reverts commits 0a4e6be9ca17c54817cf814b4b5aa60478c6df27 and 80f7fdb1c7f0f9266421f823964fd1962681f6ce. The task migration notifier was originally introduced in order to support the pvclock vsyscall with non-synchronized TSC, but KVM only supports it with synchronized TSC. Hence, on KVM the race condition is only needed due to a bad implementation on the host side, and even then it's so rare that it's mostly theoretical. As far as KVM is concerned it's possible to fix the host, avoiding the additional complexity in the vDSO and the (re)introduction of the task migration notifier. Xen, on the other hand, hasn't yet implemented vsyscall support at all, so we do not care about its plans for non-synchronized TSC. Reported-by: Peter Zijlstra <peterz@infradead.org> Suggested-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2015-04-14Merge branch 'timers-nohz-for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull NOHZ changes from Ingo Molnar: "This tree adds full dynticks support to KVM guests (support the disabling of the timer tick on the guest). The main missing piece was the recognition of guest execution as RCU extended quiescent state and related changes" * 'timers-nohz-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: kvm,rcu,nohz: use RCU extended quiescent state when running KVM guest context_tracking: Export context_tracking_user_enter/exit context_tracking: Run vtime_user_enter/exit only when state == CONTEXT_USER context_tracking: Add stub context_tracking_is_enabled context_tracking: Generalize context tracking APIs to support user and guest context_tracking: Rename context symbols to prepare for transition state ppc: Remove unused cpp symbols in kvm headers
2015-04-14Merge branch 'core-rcu-for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull RCU changes from Ingo Molnar: "The main changes in this cycle were: - changes permitting use of call_rcu() and friends very early in boot, for example, before rcu_init() is invoked. - add in-kernel API to enable and disable expediting of normal RCU grace periods. - improve RCU's handling of (hotplug-) outgoing CPUs. - NO_HZ_FULL_SYSIDLE fixes. - tiny-RCU updates to make it more tiny. - documentation updates. - miscellaneous fixes" * 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (58 commits) cpu: Provide smpboot_thread_init() on !CONFIG_SMP kernels as well cpu: Defer smpboot kthread unparking until CPU known to scheduler rcu: Associate quiescent-state reports with grace period rcu: Yet another fix for preemption and CPU hotplug rcu: Add diagnostics to grace-period cleanup rcutorture: Default to grace-period-initialization delays rcu: Handle outgoing CPUs on exit from idle loop cpu: Make CPU-offline idle-loop transition point more precise rcu: Eliminate ->onoff_mutex from rcu_node structure rcu: Process offlining and onlining only at grace-period start rcu: Move rcu_report_unblock_qs_rnp() to common code rcu: Rework preemptible expedited bitmask handling rcu: Remove event tracing from rcu_cpu_notify(), used by offline CPUs rcutorture: Enable slow grace-period initializations rcu: Provide diagnostic option to slow down grace-period initialization rcu: Detect stalls caused by failure to propagate up rcu_node tree rcu: Eliminate empty HOTPLUG_CPU ifdef rcu: Simplify sync_rcu_preempt_exp_init() rcu: Put all orphan-callback-related code under same comment rcu: Consolidate offline-CPU callback initialization ...
2015-04-13Merge branch 'for-4.1' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup Pull cgroup updates from Tejun Heo: "Nothing too interesting. Rik made cpuset cooperate better with isolcpus and there are several other cleanup patches" * 'for-4.1' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: cpuset, isolcpus: document relationship between cpusets & isolcpus cpusets, isolcpus: exclude isolcpus from load balancing in cpusets sched, isolcpu: make cpu_isolated_map visible outside scheduler cpuset: initialize cpuset a bit early cgroup: Use kvfree in pidlist_free() cgroup: call cgroup_subsys->bind on cgroup subsys initialization
2015-04-13Merge branch 'timers-core-for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull timer updates from Ingo Molnar: "The main changes in this cycle were: - clockevents state machine cleanups and enhancements (Viresh Kumar) - clockevents broadcast notifier horror to state machine conversion and related cleanups (Thomas Gleixner, Rafael J Wysocki) - clocksource and timekeeping core updates (John Stultz) - clocksource driver updates and fixes (Ben Dooks, Dmitry Osipenko, Hans de Goede, Laurent Pinchart, Maxime Ripard, Xunlei Pang) - y2038 fixes (Xunlei Pang, John Stultz) - NMI-safe ktime_get_raw_fast() and general refactoring of the clock code, in preparation to perf's per event clock ID support (Peter Zijlstra) - generic sched/clock fixes, optimizations and cleanups (Daniel Thompson) - clockevents cpu_down() race fix (Preeti U Murthy)" * 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (94 commits) timers/PM: Drop unnecessary braces from tick_freeze() timers/PM: Fix up tick_unfreeze() timekeeping: Get rid of stale comment clockevents: Cleanup dead cpu explicitely clockevents: Make tick handover explicit clockevents: Remove broadcast oneshot control leftovers sched/idle: Use explicit broadcast oneshot control function ARM: Tegra: Use explicit broadcast oneshot control function ARM: OMAP: Use explicit broadcast oneshot control function intel_idle: Use explicit broadcast oneshot control function ACPI/idle: Use explicit broadcast control function ACPI/PAD: Use explicit broadcast oneshot control function x86/amd/idle, clockevents: Use explicit broadcast oneshot control functions clockevents: Provide explicit broadcast oneshot control functions clockevents: Remove the broadcast control leftovers ARM: OMAP: Use explicit broadcast control function intel_idle: Use explicit broadcast control function cpuidle: Use explicit broadcast control function ACPI/processor: Use explicit broadcast control function ACPI/PAD: Use explicit broadcast control function ...
2015-04-13Merge branch 'sched-core-for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull scheduler changes from Ingo Molnar: "Major changes: - Reworked CPU capacity code, for better SMP load balancing on systems with assymetric CPUs. (Vincent Guittot, Morten Rasmussen) - Reworked RT task SMP balancing to be push based instead of pull based, to reduce latencies on large CPU count systems. (Steven Rostedt) - SCHED_DEADLINE support updates and fixes. (Juri Lelli) - SCHED_DEADLINE task migration support during CPU hotplug. (Wanpeng Li) - x86 mwait-idle optimizations and fixes. (Mike Galbraith, Len Brown) - sched/numa improvements. (Rik van Riel) - various cleanups" * 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (28 commits) sched/core: Drop debugging leftover trace_printk call sched/deadline: Support DL task migration during CPU hotplug sched/core: Check for available DL bandwidth in cpuset_cpu_inactive() sched/deadline: Always enqueue on previous rq when dl_task_timer() fires sched/core: Remove unused argument from init_[rt|dl]_rq() sched/deadline: Fix rt runtime corruption when dl fails its global constraints sched/deadline: Avoid a superfluous check sched: Improve load balancing in the presence of idle CPUs sched: Optimize freq invariant accounting sched: Move CFS tasks to CPUs with higher capacity sched: Add SD_PREFER_SIBLING for SMT level sched: Remove unused struct sched_group_capacity::capacity_orig sched: Replace capacity_factor by usage sched: Calculate CPU's usage statistic and put it into struct sg_lb_stats::group_usage sched: Add struct rq::cpu_capacity_orig sched: Make scale_rt invariant with frequency sched: Make sched entity usage tracking scale-invariant sched: Remove frequency scaling from cpu_capacity sched: Track group sched_entity usage contributions sched: Add sched_avg::utilization_avg_contrib ...
2015-04-13Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvmLinus Torvalds
Pull KVM updates from Paolo Bonzini: "First batch of KVM changes for 4.1 The most interesting bit here is irqfd/ioeventfd support for ARM and ARM64. Summary: ARM/ARM64: fixes for live migration, irqfd and ioeventfd support (enabling vhost, too), page aging s390: interrupt handling rework, allowing to inject all local interrupts via new ioctl and to get/set the full local irq state for migration and introspection. New ioctls to access memory by virtual address, and to get/set the guest storage keys. SIMD support. MIPS: FPU and MIPS SIMD Architecture (MSA) support. Includes some patches from Ralf Baechle's MIPS tree. x86: bugfixes (notably for pvclock, the others are small) and cleanups. Another small latency improvement for the TSC deadline timer" * tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (146 commits) KVM: use slowpath for cross page cached accesses kvm: mmu: lazy collapse small sptes into large sptes KVM: x86: Clear CR2 on VCPU reset KVM: x86: DR0-DR3 are not clear on reset KVM: x86: BSP in MSR_IA32_APICBASE is writable KVM: x86: simplify kvm_apic_map KVM: x86: avoid logical_map when it is invalid KVM: x86: fix mixed APIC mode broadcast KVM: x86: use MDA for interrupt matching kvm/ppc/mpic: drop unused IRQ_testbit KVM: nVMX: remove unnecessary double caching of MAXPHYADDR KVM: nVMX: checks for address bits beyond MAXPHYADDR on VM-entry KVM: x86: cache maxphyaddr CPUID leaf in struct kvm_vcpu KVM: vmx: pass error code with internal error #2 x86: vdso: fix pvclock races with task migration KVM: remove kvm_read_hva and kvm_read_hva_atomic KVM: x86: optimize delivery of TSC deadline timer interrupt KVM: x86: extract blocking logic from __vcpu_run kvm: x86: fix x86 eflags fixed bit KVM: s390: migrate vcpu interrupt state ...
2015-04-07mm: numa: disable change protection for vma(VM_HUGETLB)Naoya Horiguchi
Currently when a process accesses a hugetlb range protected with PROTNONE, unexpected COWs are triggered, which finally puts the hugetlb subsystem into a broken/uncontrollable state, where for example h->resv_huge_pages is subtracted too much and wraps around to a very large number, and the free hugepage pool is no longer maintainable. This patch simply stops changing protection for vma(VM_HUGETLB) to fix the problem. And this also allows us to avoid useless overhead of minor faults. Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Suggested-by: Mel Gorman <mgorman@suse.de> Cc: Hugh Dickins <hughd@google.com> Cc: "Kirill A. Shutemov" <kirill@shutemov.name> Cc: David Rientjes <rientjes@google.com> Cc: Rik van Riel <riel@redhat.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-04-03sched/core: Drop debugging leftover trace_printk callBorislav Petkov
Commit: 3c18d447b3b3 ("sched/core: Check for available DL bandwidth in cpuset_cpu_inactive()") forgot a trace_printk() debugging piece in and Steve's banner screamed in dmesg. Remove it. Signed-off-by: Borislav Petkov <bp@suse.de> Cc: Juri Lelli <juri.lelli@arm.com> Cc: Juri Lelli <juri.lelli@gmail.com> Cc: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Link: http://lkml.kernel.org/r/1428050570-21041-1-git-send-email-bp@alien8.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-04-03sched/idle: Use explicit broadcast oneshot control functionThomas Gleixner
Replace the clockevents_notify() call with an explicit function call. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/6422336.RMm7oUHcXh@vostro.rjw.lan Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-04-02sched/deadline: Support DL task migration during CPU hotplugWanpeng Li
I observed that DL tasks can't be migrated to other CPUs during CPU hotplug, in addition, task may/may not be running again if CPU is added back. The root cause which I found is that DL tasks will be throtted and removed from the DL rq after comsuming all their budget, which leads to the situation that stop task can't pick them up from the DL rq and migrate them to other CPUs during hotplug. The method to reproduce: schedtool -E -t 50000:100000 -e ./test Actually './test' is just a simple for loop. Then observe which CPU the test task is on and offline it: echo 0 > /sys/devices/system/cpu/cpuN/online This patch adds the DL task migration during CPU hotplug by finding a most suitable later deadline rq after DL timer fires if current rq is offline. If it fails to find a suitable later deadline rq then it falls back to any eligible online CPU in so that the deadline task will come back to us, and the push/pull mechanism should then move it around properly. Suggested-and-Acked-by: Juri Lelli <juri.lelli@arm.com> Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: http://lkml.kernel.org/r/1427411315-4298-1-git-send-email-wanpeng.li@linux.intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-04-02sched/core: Check for available DL bandwidth in cpuset_cpu_inactive()Juri Lelli
Hotplug operations are destructive w.r.t. cpusets. In case such an operation is performed on a CPU belonging to an exlusive cpuset, the DL bandwidth information associated with the corresponding root domain is gone even if the operation fails (in sched_cpu_inactive()). For this reason we need to move the check we currently have in sched_cpu_inactive() to cpuset_cpu_inactive() to prevent useless cpusets reconfiguration in the CPU_DOWN_FAILED path. Signed-off-by: Juri Lelli <juri.lelli@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Juri Lelli <juri.lelli@gmail.com> Link: http://lkml.kernel.org/r/1427792017-7356-2-git-send-email-juri.lelli@arm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-04-02sched/deadline: Always enqueue on previous rq when dl_task_timer() firesJuri Lelli
dl_task_timer() may fire on a different rq from where a task was removed after throttling. Since the call path is: dl_task_timer() -> enqueue_task_dl() -> enqueue_dl_entity() -> replenish_dl_entity() and replenish_dl_entity() uses dl_se's rq, we can't use current's rq in dl_task_timer(), but we need to lock the task's previous one. Tested-by: Wanpeng Li <wanpeng.li@linux.intel.com> Signed-off-by: Juri Lelli <juri.lelli@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Kirill Tkhai <ktkhai@parallels.com> Cc: Juri Lelli <juri.lelli@gmail.com> Fixes: 3960c8c0c789 ("sched: Make dl_task_time() use task_rq_lock()") Link: http://lkml.kernel.org/r/1427792017-7356-1-git-send-email-juri.lelli@arm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-04-02sched/core: Remove unused argument from init_[rt|dl]_rq()Abel Vesa
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>
2015-03-28Merge branch 'sched-urgent-for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull scheduler fix from Ingo Molnar: "A single sched/rt corner case fix for RLIMIT_RTIME correctness" * 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: sched: Fix RLIMIT_RTTIME when PI-boosting to RT
2015-03-27Merge branch 'for-mingo' of ↵Ingo Molnar
git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu Pull RCU updates from Paul E. McKenney: - Documentation updates. - Changes permitting use of call_rcu() and friends very early in boot, for example, before rcu_init() is invoked. - Miscellaneous fixes. - Add in-kernel API to enable and disable expediting of normal RCU grace periods. - Improve RCU's handling of (hotplug-) outgoing CPUs. Note: ARM support is lagging a bit here, and these improved diagnostics might generate (harmless) splats. - NO_HZ_FULL_SYSIDLE fixes. - Tiny RCU updates to make it more tiny. Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-03-27sched/deadline: Fix rt runtime corruption when dl fails its global constraintsWanpeng Li
One version of sched_rt_global_constaints() (the !rt-cgroup one) changes state, therefore if we fail the later sched_dl_global_constraints() call the state is left in an inconsistent state. Fix this by changing the order of the calls. Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com> [ Improved the changelog. ] Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Juri Lelli <juri.lelli@arm.com> Link: http://lkml.kernel.org/r/1426590931-4639-2-git-send-email-wanpeng.li@linux.intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-03-27sched/deadline: Avoid a superfluous checkWanpeng Li
Since commit 40767b0dc768 ("sched/deadline: Fix deadline parameter modification handling") we clear the thottled state when switching from a dl task, therefore we should never find it set in switching to a dl task. Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com> [ Improved the changelog. ] Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Juri Lelli <juri.lelli@arm.com> Link: http://lkml.kernel.org/r/1426590931-4639-1-git-send-email-wanpeng.li@linux.intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-03-27sched: Improve load balancing in the presence of idle CPUsPreeti U Murthy
When a CPU is kicked to do nohz idle balancing, it wakes up to do load balancing on itself, followed by load balancing on behalf of idle CPUs. But it may end up with load after the load balancing attempt on itself. This aborts nohz idle balancing. As a result several idle CPUs are left without tasks till such a time that an ILB CPU finds it unfavorable to pull tasks upon itself. This delays spreading of load across idle CPUs and worse, clutters only a few CPUs with tasks. The effect of the above problem was observed on an SMT8 POWER server with 2 levels of numa domains. Busy loops equal to number of cores were spawned. Since load balancing on fork/exec is discouraged across numa domains, all busy loops would start on one of the numa domains. However it was expected that eventually one busy loop would run per core across all domains due to nohz idle load balancing. But it was observed that it took as long as 10 seconds to spread the load across numa domains. Further investigation showed that this was a consequence of the following: 1. An ILB CPU was chosen from the first numa domain to trigger nohz idle load balancing [Given the experiment, upto 6 CPUs per core could be potentially idle in this domain.] 2. However the ILB CPU would call load_balance() on itself before initiating nohz idle load balancing. 3. Given cores are SMT8, the ILB CPU had enough opportunities to pull tasks from its sibling cores to even out load. 4. Now that the ILB CPU was no longer idle, it would abort nohz idle load balancing As a result the opportunities to spread load across numa domains were lost until such a time that the cores within the first numa domain had equal number of tasks among themselves. This is a pretty bad scenario, since the cores within the first numa domain would have as many as 4 tasks each, while cores in the neighbouring numa domains would all remain idle. Fix this, by checking if a CPU was woken up to do nohz idle load balancing, before it does load balancing upon itself. This way we allow idle CPUs across the system to do load balancing which results in quicker spread of load, instead of performing load balancing within the local sched domain hierarchy of the ILB CPU alone under circumstances such as above. Signed-off-by: Preeti U Murthy <preeti@linux.vnet.ibm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Jason Low <jason.low2@hp.com> Cc: benh@kernel.crashing.org Cc: daniel.lezcano@linaro.org Cc: efault@gmx.de Cc: iamjoonsoo.kim@lge.com Cc: morten.rasmussen@arm.com Cc: pjt@google.com Cc: riel@redhat.com Cc: srikar@linux.vnet.ibm.com Cc: svaidy@linux.vnet.ibm.com Cc: tim.c.chen@linux.intel.com Cc: vincent.guittot@linaro.org Link: http://lkml.kernel.org/r/20150326130014.21532.17158.stgit@preeti.in.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-03-27sched: Optimize freq invariant accountingPeter Zijlstra
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>
2015-03-27sched: Move CFS tasks to CPUs with higher capacityVincent Guittot
When a CPU is used to handle a lot of IRQs or some RT tasks, the remaining capacity for CFS tasks can be significantly reduced. Once we detect such situation by comparing cpu_capacity_orig and cpu_capacity, we trig an idle load balance to check if it's worth moving its tasks on an idle CPU. It's worth trying to move the task before the CPU is fully utilized to minimize the preemption by irq or RT tasks. Once the idle load_balance has selected the busiest CPU, it will look for an active load balance for only two cases: - There is only 1 task on the busiest CPU. - We haven't been able to move a task of the busiest rq. A CPU with a reduced capacity is included in the 1st case, and it's worth to actively migrate its task if the idle CPU has got more available capacity for CFS tasks. This test has been added in need_active_balance. As a sidenote, this will not generate more spurious ilb because we already trig an ilb if there is more than 1 busy cpu. If this cpu is the only one that has a task, we will trig the ilb once for migrating the task. The nohz_kick_needed function has been cleaned up a bit while adding the new test env.src_cpu and env.src_rq must be set unconditionnally because they are used in need_active_balance which is called even if busiest->nr_running equals 1 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/1425052454-25797-12-git-send-email-vincent.guittot@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-03-27sched: Add SD_PREFER_SIBLING for SMT levelVincent Guittot
Add the SD_PREFER_SIBLING flag for SMT level in order to ensure that the scheduler will place at least one task per core. Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Preeti U. Murthy <preeti@linux.vnet.ibm.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: riel@redhat.com Link: http://lkml.kernel.org/r/1425052454-25797-11-git-send-email-vincent.guittot@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-03-27sched: Remove unused struct sched_group_capacity::capacity_origVincent Guittot
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>
2015-03-27sched: Replace capacity_factor by usageVincent Guittot
The scheduler tries to compute how many tasks a group of CPUs can handle by assuming that a task's load is SCHED_LOAD_SCALE and a CPU's capacity is SCHED_CAPACITY_SCALE. 'struct sg_lb_stats:group_capacity_factor' divides the capacity of the group by SCHED_LOAD_SCALE to estimate how many task can run in the group. Then, it compares this value with the sum of nr_running to decide if the group is overloaded or not. But the 'group_capacity_factor' concept is hardly working for SMT systems, it sometimes works for big cores but fails to do the right thing for little cores. Below are two examples to illustrate the problem that this patch solves: 1- If the original capacity of a CPU is less than SCHED_CAPACITY_SCALE (640 as an example), a group of 3 CPUS will have a max capacity_factor of 2 (div_round_closest(3x640/1024) = 2) which means that it will be seen as overloaded even if we have only one task per CPU. 2 - If the original capacity of a CPU is greater than SCHED_CAPACITY_SCALE (1512 as an example), a group of 4 CPUs will have a capacity_factor of 4 (at max and thanks to the fix [0] for SMT system that prevent the apparition of ghost CPUs) but if one CPU is fully used by rt tasks (and its capacity is reduced to nearly nothing), the capacity factor of the group will still be 4 (div_round_closest(3*1512/1024) = 5 which is cap to 4 with [0]). So, this patch tries to solve this issue by removing capacity_factor and replacing it with the 2 following metrics: - The available CPU's capacity for CFS tasks which is already used by load_balance(). - The usage of the CPU by the CFS tasks. For the latter, utilization_avg_contrib has been re-introduced to compute the usage of a CPU by CFS tasks. 'group_capacity_factor' and 'group_has_free_capacity' has been removed and replaced by 'group_no_capacity'. We compare the number of task with the number of CPUs and we evaluate the level of utilization of the CPUs to define if a group is overloaded or if a group has capacity to handle more tasks. For SD_PREFER_SIBLING, a group is tagged overloaded if it has more than 1 task so it will be selected in priority (among the overloaded groups). Since [1], SD_PREFER_SIBLING is no more concerned by the computation of 'load_above_capacity' because local is not overloaded. [1] 9a5d9ba6a363 ("sched/fair: Allow calculate_imbalance() to move idle cpus") 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 Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/1425052454-25797-9-git-send-email-vincent.guittot@linaro.org [ Tidied up the changelog. ] Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-03-27sched: Calculate CPU's usage statistic and put it into struct ↵Vincent Guittot
sg_lb_stats::group_usage Monitor the usage level of each group of each sched_domain level. The usage is the portion of cpu_capacity_orig that is currently used on a CPU or group of CPUs. We use the utilization_load_avg to evaluate the usage level of each group. The utilization_load_avg only takes into account the running time of the CFS tasks on a CPU with a maximum value of SCHED_LOAD_SCALE when the CPU is fully utilized. Nevertheless, we must cap utilization_load_avg which can be temporally greater than SCHED_LOAD_SCALE after the migration of a task on this CPU and until the metrics are stabilized. The utilization_load_avg is in the range [0..SCHED_LOAD_SCALE] to reflect the running load on the CPU whereas the available capacity for the CFS task is in the range [0..cpu_capacity_orig]. In order to test if a CPU is fully utilized by CFS tasks, we have to scale the utilization in the cpu_capacity_orig range of the CPU to get the usage of the latter. The usage can then be compared with the available capacity (ie cpu_capacity) to deduct the usage level of a CPU. The frequency scaling invariance of the usage is not taken into account in this patch, it will be solved in another patch which will deal with frequency scaling invariance on the utilization_load_avg. 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/1425455327-13508-1-git-send-email-vincent.guittot@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-03-27sched: Add struct rq::cpu_capacity_origVincent Guittot
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>
2015-03-27sched: Make scale_rt invariant with frequencyVincent Guittot
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>
2015-03-27sched: Make sched entity usage tracking scale-invariantMorten Rasmussen
Apply frequency scale-invariance correction factor to usage tracking. Each segment of the running_avg_sum geometric series is now scaled by the current frequency so the utilization_avg_contrib of each entity will be invariant with frequency scaling. As a result, utilization_load_avg which is the sum of utilization_avg_contrib, becomes invariant too. So the usage level that is returned by get_cpu_usage(), stays relative to the max frequency as the cpu_capacity which is is compared against. Then, we want the keep the load tracking values in a 32-bit type, which implies that the max value of {runnable|running}_avg_sum must be lower than 2^32/88761=48388 (88761 is the max weigth of a task). As LOAD_AVG_MAX = 47742, arch_scale_freq_capacity() must return a value less than (48388/47742) << SCHED_CAPACITY_SHIFT = 1037 (SCHED_SCALE_CAPACITY = 1024). So we define the range to [0..SCHED_SCALE_CAPACITY] in order to avoid overflow. Signed-off-by: Morten Rasmussen <morten.rasmussen@arm.com> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> 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/1425455186-13451-1-git-send-email-vincent.guittot@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-03-27sched: Remove frequency scaling from cpu_capacityVincent Guittot
Now that arch_scale_cpu_capacity has been introduced to scale the original capacity, the arch_scale_freq_capacity is no longer used (it was previously used by ARM arch). Remove arch_scale_freq_capacity from the computation of cpu_capacity. The frequency invariance will be handled in the load tracking and not in the CPU capacity. arch_scale_freq_capacity will be revisited for scaling load with the current frequency of the CPUs in a later patch. 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/1425052454-25797-4-git-send-email-vincent.guittot@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-03-27sched: Track group sched_entity usage contributionsMorten Rasmussen
Add usage contribution tracking for group entities. Unlike se->avg.load_avg_contrib, se->avg.utilization_avg_contrib for group entities is the sum of se->avg.utilization_avg_contrib for all entities on the group runqueue. It is _not_ influenced in any way by the task group h_load. Hence it is representing the actual cpu usage of the group, not its intended load contribution which may differ significantly from the utilization on lightly utilized systems. Signed-off-by: Morten Rasmussen <morten.rasmussen@arm.com> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> 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/1425052454-25797-3-git-send-email-vincent.guittot@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-03-27sched: Add sched_avg::utilization_avg_contribVincent Guittot
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>
2015-03-25mm: numa: slow PTE scan rate if migration failures occurMel Gorman
Dave Chinner reported the following on https://lkml.org/lkml/2015/3/1/226 Across the board the 4.0-rc1 numbers are much slower, and the degradation is far worse when using the large memory footprint configs. Perf points straight at the cause - this is from 4.0-rc1 on the "-o bhash=101073" config: - 56.07% 56.07% [kernel] [k] default_send_IPI_mask_sequence_phys - default_send_IPI_mask_sequence_phys - 99.99% physflat_send_IPI_mask - 99.37% native_send_call_func_ipi smp_call_function_many - native_flush_tlb_others - 99.85% flush_tlb_page ptep_clear_flush try_to_unmap_one rmap_walk try_to_unmap migrate_pages migrate_misplaced_page - handle_mm_fault - 99.73% __do_page_fault trace_do_page_fault do_async_page_fault + async_page_fault 0.63% native_send_call_func_single_ipi generic_exec_single smp_call_function_single This is showing excessive migration activity even though excessive migrations are meant to get throttled. Normally, the scan rate is tuned on a per-task basis depending on the locality of faults. However, if migrations fail for any reason then the PTE scanner may scan faster if the faults continue to be remote. This means there is higher system CPU overhead and fault trapping at exactly the time we know that migrations cannot happen. This patch tracks when migration failures occur and slows the PTE scanner. Signed-off-by: Mel Gorman <mgorman@suse.de> Reported-by: Dave Chinner <david@fromorbit.com> Tested-by: Dave Chinner <david@fromorbit.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Aneesh Kumar <aneesh.kumar@linux.vnet.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-03-23x86: kvm: Revert "remove sched notifier for cross-cpu migrations"Marcelo Tosatti
The following point: 2. per-CPU pvclock time info is updated if the underlying CPU changes. Is not true anymore since "KVM: x86: update pvclock area conditionally, on cpu migration". Add task migration notification back. Problem noticed by Andy Lutomirski. Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> CC: stable@kernel.org # 3.11+
2015-03-23sched/rt: Use IPI to trigger RT task push migration instead of pullingSteven Rostedt
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>
2015-03-23Merge branch 'sched/urgent' into sched/core, to pick up fixes before ↵Ingo Molnar
applying new patches Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-03-23sched: Fix RLIMIT_RTTIME when PI-boosting to RTBrian Silverman
When non-realtime tasks get priority-inheritance boosted to a realtime scheduling class, RLIMIT_RTTIME starts to apply to them. However, the counter used for checking this (the same one used for SCHED_RR timeslices) was not getting reset. This meant that tasks running with a non-realtime scheduling class which are repeatedly boosted to a realtime one, but never block while they are running realtime, eventually hit the timeout without ever running for a time over the limit. This patch resets the realtime timeslice counter when un-PI-boosting from an RT to a non-RT scheduling class. I have some test code with two threads and a shared PTHREAD_PRIO_INHERIT mutex which induces priority boosting and spins while boosted that gets killed by a SIGXCPU on non-fixed kernels but doesn't with this patch applied. It happens much faster with a CONFIG_PREEMPT_RT kernel, and does happen eventually with PREEMPT_VOLUNTARY kernels. Signed-off-by: Brian Silverman <brian@peloton-tech.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: austin@peloton-tech.com Cc: <stable@vger.kernel.org> Link: http://lkml.kernel.org/r/1424305436-6716-1-git-send-email-brian@peloton-tech.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-03-19sched, isolcpu: make cpu_isolated_map visible outside schedulerRik van Riel
Needed by the next patch. Also makes cpu_isolated_map present when compiled without SMP and/or with CONFIG_NR_CPUS=1, like the other cpu masks. At some point we may want to clean things up so cpumasks do not exist in UP kernels. Maybe something for the CONFIG_TINY crowd. Cc: Peter Zijlstra <peterz@infradead.org> Cc: Clark Williams <williams@redhat.com> Cc: Li Zefan <lizefan@huawei.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Luiz Capitulino <lcapitulino@redhat.com> Cc: David Rientjes <rientjes@google.com> Cc: Mike Galbraith <umgwanakikbuti@gmail.com> Cc: cgroups@vger.kernel.org Signed-off-by: Rik van Riel <riel@redhat.com> Acked-by: Zefan Li <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org>
2015-03-12rcu: Handle outgoing CPUs on exit from idle loopPaul E. McKenney
This commit informs RCU of an outgoing CPU just before that CPU invokes arch_cpu_idle_dead() during its last pass through the idle loop (via a new CPU_DYING_IDLE notifier value). This change means that RCU need not deal with outgoing CPUs passing through the scheduler after informing RCU that they are no longer online. Note that removing the CPU from the rcu_node ->qsmaskinit bit masks is done at CPU_DYING_IDLE time, and orphaning callbacks is still done at CPU_DEAD time, the reason being that at CPU_DEAD time we have another CPU that can adopt them. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2015-03-12cpu: Make CPU-offline idle-loop transition point more precisePaul E. McKenney
This commit uses a per-CPU variable to make the CPU-offline code path through the idle loop more precise, so that the outgoing CPU is guaranteed to make it into the idle loop before it is powered off. This commit is in preparation for putting the RCU offline-handling code on this code path, which will eliminate the magic one-jiffy wait that RCU uses as the maximum time for an outgoing CPU to get all the way through the scheduler. The magic one-jiffy wait for incoming CPUs remains a separate issue. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2015-03-10sched/deadline: Add rq->clock update skip for dl task yieldWanpeng Li
This patch adds rq->clock update skip for SCHED_DEADLINE task yield, to tell update_rq_clock() that we've just updated the clock, so that we don't do a microscopic update in schedule() and double the fastpath cost. Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com> Cc: Juri Lelli <juri.lelli@arm.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1425961200-3809-1-git-send-email-wanpeng.li@linux.intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-03-09context_tracking: Rename context symbols to prepare for transition stateFrederic Weisbecker
Current context tracking symbols are designed to express living state. As such they are prefixed with "IN_": IN_USER, IN_KERNEL. Now we are going to use these symbols to also express state transitions such as context_tracking_enter(IN_USER) or context_tracking_exit(IN_USER). But while the "IN_" prefix works well to express entering a context, it's confusing to depict a context exit: context_tracking_exit(IN_USER) could mean two things: 1) We are exiting the current context to enter user context. 2) We are exiting the user context We want 2) but the reviewer may be confused and understand 1) So lets disambiguate these symbols and rename them to CONTEXT_USER and CONTEXT_KERNEL. Acked-by: Rik van Riel <riel@redhat.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Will deacon <will.deacon@arm.com> Cc: Marcelo Tosatti <mtosatti@redhat.com> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Cc: Luiz Capitulino <lcapitulino@redhat.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
2015-03-05cpuidle / sleep: Use broadcast timer for states that stop local timerRafael J. Wysocki
Commit 381063133246 (PM / sleep: Re-implement suspend-to-idle handling) overlooked the fact that entering some sufficiently deep idle states by CPUs may cause their local timers to stop and in those cases it is necessary to switch over to a broadcast timer prior to entering the idle state. If the cpuidle driver in use does not provide the new ->enter_freeze callback for any of the idle states, that problem affects suspend-to-idle too, but it is not taken into account after the changes made by commit 381063133246. Fix that by changing the definition of cpuidle_enter_freeze() and re-arranging of the code in cpuidle_idle_call(), so the former does not call cpuidle_enter() any more and the fallback case is handled by cpuidle_idle_call() directly. Fixes: 381063133246 (PM / sleep: Re-implement suspend-to-idle handling) Reported-and-tested-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
2015-03-02cpuidle: Clean up fallback handling in cpuidle_idle_call()Rafael J. Wysocki
Move the fallback code path in cpuidle_idle_call() to the end of the function to avoid jumping to a label in an if () branch. Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2015-02-28idle / sleep: Avoid excessive disabling and enabling interruptsRafael J. Wysocki
Disabling interrupts at the end of cpuidle_enter_freeze() is not useful, because its caller, cpuidle_idle_call(), re-enables them right away after invoking it. To avoid that unnecessary back and forth dance with interrupts, make cpuidle_enter_freeze() enable interrupts after calling enter_freeze_proper() and drop the local_irq_disable() at its end, so that all of the code paths in it end up with interrupts enabled. Then, cpuidle_idle_call() will not need to re-enable interrupts after calling cpuidle_enter_freeze() any more, because the latter will return with interrupts enabled, in analogy with cpuidle_enter(). Reported-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
2015-02-21Merge branch 'sched-urgent-for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull scheduler fixes from Ingo Molnar: "Thiscontains misc fixes: preempt_schedule_common() and io_schedule() recursion fixes, sched/dl fixes, a completion_done() revert, two sched/rt fixes and a comment update patch" * 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: sched/rt: Avoid obvious configuration fail sched/autogroup: Fix failure to set cpu.rt_runtime_us sched/dl: Do update_rq_clock() in yield_task_dl() sched: Prevent recursion in io_schedule() sched/completion: Serialize completion_done() with complete() sched: Fix preempt_schedule_common() triggering tracing recursion sched/dl: Prevent enqueue of a sleeping task in dl_task_timer() sched: Make dl_task_time() use task_rq_lock() sched: Clarify ordering between task_rq_lock() and move_queued_task()
2015-02-18sched/rt/nohz: Stop scheduler tick if running realtime taskRik van Riel
If the CPU is running a realtime task that does not round-robin with another realtime task of equal priority, there is no point in keeping the scheduler tick going. After all, whenever the scheduler tick runs, the kernel will just decide not to reschedule. Extend sched_can_stop_tick() to recognize these situations, and inform the rest of the kernel that the scheduler tick can be stopped. Tested-by: Luiz Capitulino <lcapitulino@redhat.com> Signed-off-by: Rik van Riel <riel@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: fweisbec@redhat.com Cc: mtosatti@redhat.com Link: http://lkml.kernel.org/r/20150216152349.6a8ed824@annuminas.surriel.com [ Small cleanliness tweak. ] Signed-off-by: Ingo Molnar <mingo@kernel.org>