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- 30 Nov, 2017 1 commit
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Steven Rostedt (Red Hat) authored
commit 4bdced5c upstream. When a CPU lowers its priority (schedules out a high priority task for a lower priority one), a check is made to see if any other CPU has overloaded RT tasks (more than one). It checks the rto_mask to determine this and if so it will request to pull one of those tasks to itself if the non running RT task is of higher priority than the new priority of the next task to run on the current CPU. When we deal with large number of CPUs, the original pull logic suffered from large lock contention on a single CPU run queue, which caused a huge latency across all CPUs. This was caused by only having one CPU having overloaded RT tasks and a bunch of other CPUs lowering their priority. To solve this issue, commit: b6366f04 ("sched/rt: Use IPI to trigger RT task push migration instead of pulling") changed the way to request a pull. Instead of grabbing the lock of the overloaded CPU's runqueue, it simply sent an IPI to that CPU to do the work. Although the IPI logic worked very well in removing the large latency build up, it still could suffer from a large number of IPIs being sent to a single CPU. On a 80 CPU box, I measured over 200us of processing IPIs. Worse yet, when I tested this on a 120 CPU box, with a stress test that had lots of RT tasks scheduling on all CPUs, it actually triggered the hard lockup detector! One CPU had so many IPIs sent to it, and due to the restart mechanism that is triggered when the source run queue has a priority status change, the CPU spent minutes! processing the IPIs. Thinking about this further, I realized there's no reason for each run queue to send its own IPI. As all CPUs with overloaded tasks must be scanned regardless if there's one or many CPUs lowering their priority, because there's no current way to find the CPU with the highest priority task that can schedule to one of these CPUs, there really only needs to be one IPI being sent around at a time. This greatly simplifies the code! The new approach is to have each root domain have its own irq work, as the rto_mask is per root domain. The root domain has the following fields attached to it: rto_push_work - the irq work to process each CPU set in rto_mask rto_lock - the lock to protect some of the other rto fields rto_loop_start - an atomic that keeps contention down on rto_lock the first CPU scheduling in a lower priority task is the one to kick off the process. rto_loop_next - an atomic that gets incremented for each CPU that schedules in a lower priority task. rto_loop - a variable protected by rto_lock that is used to compare against rto_loop_next rto_cpu - The cpu to send the next IPI to, also protected by the rto_lock. When a CPU schedules in a lower priority task and wants to make sure overloaded CPUs know about it. It increments the rto_loop_next. Then it atomically sets rto_loop_start with a cmpxchg. If the old value is not "0", then it is done, as another CPU is kicking off the IPI loop. If the old value is "0", then it will take the rto_lock to synchronize with a possible IPI being sent around to the overloaded CPUs. If rto_cpu is greater than or equal to nr_cpu_ids, then there's either no IPI being sent around, or one is about to finish. Then rto_cpu is set to the first CPU in rto_mask and an IPI is sent to that CPU. If there's no CPUs set in rto_mask, then there's nothing to be done. When the CPU receives the IPI, it will first try to push any RT tasks that is queued on the CPU but can't run because a higher priority RT task is currently running on that CPU. Then it takes the rto_lock and looks for the next CPU in the rto_mask. If it finds one, it simply sends an IPI to that CPU and the process continues. If there's no more CPUs in the rto_mask, then rto_loop is compared with rto_loop_next. If they match, everything is done and the process is over. If they do not match, then a CPU scheduled in a lower priority task as the IPI was being passed around, and the process needs to start again. The first CPU in rto_mask is sent the IPI. This change removes this duplication of work in the IPI logic, and greatly lowers the latency caused by the IPIs. This removed the lockup happening on the 120 CPU machine. It also simplifies the code tremendously. What else could anyone ask for? Thanks to Peter Zijlstra for simplifying the rto_loop_start atomic logic and supplying me with the rto_start_trylock() and rto_start_unlock() helper functions. Signed-off-by:
Steven Rostedt (VMware) <rostedt@goodmis.org> Signed-off-by:
Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Clark Williams <williams@redhat.com> Cc: Daniel Bristot de Oliveira <bristot@redhat.com> Cc: John Kacur <jkacur@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Scott Wood <swood@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20170424114732.1aac6dc4@gandalf.local.homeSigned-off-by:
Ingo Molnar <mingo@kernel.org> Signed-off-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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- 31 Mar, 2017 1 commit
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Sebastian Andrzej Siewior authored
commit 619bd4a7 upstream. Since the change in commit: fd7a4bed ("sched, rt: Convert switched_{from, to}_rt() / prio_changed_rt() to balance callbacks") ... we don't reschedule a task under certain circumstances: Lets say task-A, SCHED_OTHER, is running on CPU0 (and it may run only on CPU0) and holds a PI lock. This task is removed from the CPU because it used up its time slice and another SCHED_OTHER task is running. Task-B on CPU1 runs at RT priority and asks for the lock owned by task-A. This results in a priority boost for task-A. Task-B goes to sleep until the lock has been made available. Task-A is already runnable (but not active), so it receives no wake up. The reality now is that task-A gets on the CPU once the scheduler decides to remove the current task despite the fact that a high priority task is enqueued and waiting. This may take a long time. The desired behaviour is that CPU0 immediately reschedules after the priority boost which made task-A the task with the lowest priority. Suggested-by:
Peter Zijlstra <peterz@infradead.org> Signed-off-by:
Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by:
Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Thomas Gleixner <tglx@linutronix.de> Fixes: fd7a4bed ("sched, rt: Convert switched_{from, to}_rt() prio_changed_rt() to balance callbacks") Link: http://lkml.kernel.org/r/20170124144006.29821-1-bigeasy@linutronix.deSigned-off-by:
Ingo Molnar <mingo@kernel.org> Signed-off-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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- 16 Aug, 2016 2 commits
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Rafael J. Wysocki authored
All of the callers of cpufreq_update_util() pass rq_clock(rq) to it as the time argument and some of them check whether or not cpu_of(rq) is equal to smp_processor_id() before calling it, so rework it to take a runqueue pointer as the argument and move the rq_clock(rq) evaluation into it. Additionally, provide a wrapper checking cpu_of(rq) against smp_processor_id() for the cpufreq_update_util() callers that need it. Signed-off-by:
Rafael J. Wysocki <rafael.j.wysocki@intel.com> Acked-by:
Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by:
Viresh Kumar <viresh.kumar@linaro.org>
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Rafael J. Wysocki authored
It is useful to know the reason why cpufreq_update_util() has just been called and that can be passed as flags to cpufreq_update_util() and to the ->func() callback in struct update_util_data. However, doing that in addition to passing the util and max arguments they already take would be clumsy, so avoid it. Instead, use the observation that the schedutil governor is part of the scheduler proper, so it can access scheduler data directly. This allows the util and max arguments of cpufreq_update_util() and the ->func() callback in struct update_util_data to be replaced with a flags one, but schedutil has to be modified to follow. Thus make the schedutil governor obtain the CFS utilization information from the scheduler and use the "RT" and "DL" flags instead of the special utilization value of ULONG_MAX to track updates from the RT and DL sched classes. Make it non-modular too to avoid having to export scheduler variables to modules at large. Next, update all of the other users of cpufreq_update_util() and the ->func() callback in struct update_util_data accordingly. Suggested-by:
Peter Zijlstra <peterz@infradead.org> Signed-off-by:
Rafael J. Wysocki <rafael.j.wysocki@intel.com> Acked-by:
Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by:
Viresh Kumar <viresh.kumar@linaro.org>
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- 12 May, 2016 1 commit
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Thomas Gleixner authored
tsk_nr_cpus_allowed() is an accessor for task->nr_cpus_allowed which allows us to change the representation of ->nr_cpus_allowed if required. Signed-off-by:
Thomas Gleixner <tglx@linutronix.de> Signed-off-by:
Sebastian Andrzej Siewior <bigeasy@linutronix.de> 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: linux-kernel@vger.kernel.org Link: http://lkml.kernel.org/r/1462969411-17735-2-git-send-email-bigeasy@linutronix.deSigned-off-by:
Ingo Molnar <mingo@kernel.org>
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- 10 May, 2016 1 commit
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Xunlei Pang authored
We got this warning: WARNING: CPU: 1 PID: 2468 at kernel/sched/core.c:1161 set_task_cpu+0x1af/0x1c0 [...] Call Trace: dump_stack+0x63/0x87 __warn+0xd1/0xf0 warn_slowpath_null+0x1d/0x20 set_task_cpu+0x1af/0x1c0 push_dl_task.part.34+0xea/0x180 push_dl_tasks+0x17/0x30 __balance_callback+0x45/0x5c __sched_setscheduler+0x906/0xb90 SyS_sched_setattr+0x150/0x190 do_syscall_64+0x62/0x110 entry_SYSCALL64_slow_path+0x25/0x25 This corresponds to: WARN_ON_ONCE(p->state == TASK_RUNNING && p->sched_class == &fair_sched_class && (p->on_rq && !task_on_rq_migrating(p))) It happens because in find_lock_later_rq(), the task whose scheduling class was changed to fair class is still pushed away as if it were a deadline task ... So, check in find_lock_later_rq() after double_lock_balance(), if the scheduling class of the deadline task was changed, break and retry. Apply the same logic to RT tasks. Signed-off-by:
Xunlei Pang <xlpang@redhat.com> Reviewed-by:
Steven Rostedt <rostedt@goodmis.org> Acked-by:
Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Juri Lelli <juri.lelli@arm.com> Link: http://lkml.kernel.org/r/1462767091-1215-1-git-send-email-xlpang@redhat.comSigned-off-by:
Ingo Molnar <mingo@kernel.org>
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- 05 May, 2016 1 commit
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Peter Zijlstra authored
The problem with the existing lock pinning is that each pin is of value 1; this mean you can simply unpin if you know its pinned, without having any extra information. This scheme generates a random (16 bit) cookie for each pin and requires this same cookie to unpin. This means you have to keep the cookie in context. No objsize difference for !LOCKDEP kernels. 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> Cc: linux-kernel@vger.kernel.org Signed-off-by:
Ingo Molnar <mingo@kernel.org>
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- 28 Apr, 2016 1 commit
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Wanpeng Li authored
Sometimes delta_exec is 0 due to update_curr() is called multiple times, this is captured by: u64 delta_exec = rq_clock_task(rq) - curr->se.exec_start; This patch optimizes the cpufreq update kicker by bailing out when nothing changed, it will benefit the upcoming schedutil, since otherwise it will (over)react to the special util/max combination. Signed-off-by:
Wanpeng Li <wanpeng.li@hotmail.com> Signed-off-by:
Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1461316044-9520-1-git-send-email-wanpeng.li@hotmail.comSigned-off-by:
Ingo Molnar <mingo@kernel.org>
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- 09 Mar, 2016 1 commit
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Rafael J. Wysocki authored
Introduce a mechanism by which parts of the cpufreq subsystem ("setpolicy" drivers or the core) can register callbacks to be executed from cpufreq_update_util() which is invoked by the scheduler's update_load_avg() on CPU utilization changes. This allows the "setpolicy" drivers to dispense with their timers and do all of the computations they need and frequency/voltage adjustments in the update_load_avg() code path, among other things. The update_load_avg() changes were suggested by Peter Zijlstra. Signed-off-by:
Rafael J. Wysocki <rafael.j.wysocki@intel.com> Acked-by:
Viresh Kumar <viresh.kumar@linaro.org> Acked-by:
Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by:
Ingo Molnar <mingo@kernel.org>
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- 02 Mar, 2016 1 commit
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Frederic Weisbecker authored
In order to evaluate the scheduler tick dependency without probing context switches, we need to know how much SCHED_RR and SCHED_FIFO tasks are enqueued as those policies don't have the same preemption requirements. To prepare for that, let's account SCHED_RR tasks, we'll be able to deduce SCHED_FIFO tasks as well from it and the total RT tasks in the runqueue. Reviewed-by:
Chris Metcalf <cmetcalf@ezchip.com> Cc: Christoph Lameter <cl@linux.com> Cc: Chris Metcalf <cmetcalf@ezchip.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Luiz Capitulino <lcapitulino@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rik van Riel <riel@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Viresh Kumar <viresh.kumar@linaro.org> Signed-off-by:
Frederic Weisbecker <fweisbec@gmail.com>
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- 29 Feb, 2016 2 commits
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Steven Rostedt authored
I've been debugging why deadline tasks can cause the RT scheduler to throttle, even when the deadline tasks are only taking up 50% of the CPU and RT tasks are not even using 1% of the CPU. Here's what I found. In order to keep a CPU from being hogged by RT tasks, the deadline scheduler adds its run time (delta_exec) to the rt_time of the RT bandwidth. That way, if the two use more than 95% of the CPU within one second (default settings), the RT tasks are throttled to allow non RT tasks to run. Although the deadline tasks add their run time to the RT bandwidth, it lets the RT tasks do the accounting. This is where the problem lies. If a deadline task runs for a bit, and no RT tasks are running, then it will continually add to the RT rt_time that is used to calculate how much CPU the RT tasks use. But no RT period is in play, and this accumulation of the runtime never gets reset. When an RT task finally gets to run, and the watchdog goes off, it can see that the RT task has used more than it should of, because the deadline task added all this runtime to its rt_time. Then the RT task that just woke up gets throttled for no good reason. I also noticed that when an RT task is queued, it starts the timer to account for overload and such. But that timer goes off one period later, which may be too late and the extra rt_time will trigger a throttle. This is a quick work around to the problem. When a new RT task is queued, the bandwidth timer is set to go off immediately. Then the timer can clear out the extra time added to the rt_time while there was no RT task running. This stops my tests from triggering the throttle, and it will still throttle if an RT task runs too much, even while a deadline task is running. A better solution may be to subtract the bandwidth that the deadline task uses from the rt_runtime, and add it back when its finished. Then there wont be a need for runtime tracking of the time used by deadline tasks. I may play with that solution tomorrow. Signed-off-by:
Steven Rostedt <rostedt@goodmis.org> Signed-off-by:
Peter Zijlstra (Intel) <peterz@infradead.org> Cc: <juri.lelli@gmail.com> Cc: <williams@redhat.com> Cc: Clark Williams Cc: Daniel Bristot de Oliveira <bristot@redhat.com> Cc: John Kacur <jkacur@redhat.com> Cc: Juri Lelli 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/20160216183746.349ec98b@gandalf.local.homeSigned-off-by:
Ingo Molnar <mingo@kernel.org>
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Peter Zijlstra authored
Andrea Parri reported: > I found that the following scenario (with CONFIG_RT_GROUP_SCHED=y) is not > handled correctly: > > T1 (prio = 20) > lock(rtmutex); > > T2 (prio = 20) > blocks on rtmutex (rt_nr_boosted = 0 on T1's rq) > > T1 (prio = 20) > sys_set_scheduler(prio = 0) > [new_effective_prio == oldprio] > T1 prio = 20 (rt_nr_boosted = 0 on T1's rq) > > The last step is incorrect as T1 is now boosted (c.f., rt_se_boosted()); > in particular, if we continue with > > T1 (prio = 20) > unlock(rtmutex) > wakeup(T2) > adjust_prio(T1) > [prio != rt_mutex_getprio(T1)] > dequeue(T1) > rt_nr_boosted = (unsigned long)(-1) > ... > T1 prio = 0 > > then we end up leaving rt_nr_boosted in an "inconsistent" state. > > The simple program attached could reproduce the previous scenario; note > that, as a consequence of the presence of this state, the "assertion" > > WARN_ON(!rt_nr_running && rt_nr_boosted) > > from dec_rt_group() may trigger. So normally we dequeue/enqueue tasks in sched_setscheduler(), which would ensure the accounting stays correct. However in the early PI path we fail to do so. So this was introduced at around v3.14, by: c365c292 ("sched: Consider pi boosting in setscheduler()") which fixed another problem exactly because that dequeue/enqueue, joy. Fix this by teaching rt about DEQUEUE_SAVE/ENQUEUE_RESTORE and have it preserve runqueue location with that option. This requires decoupling the on_rt_rq() state from being on the list. In order to allow for explicit movement during the SAVE/RESTORE, introduce {DE,EN}QUEUE_MOVE. We still must use SAVE/RESTORE in these cases to preserve other invariants. Respecting the SAVE/RESTORE flags also has the (nice) side-effect that things like sys_nice()/sys_sched_setaffinity() also do not reorder FIFO tasks (whereas they used to before this patch). Reported-by:
Andrea Parri <parri.andrea@gmail.com> Tested-by:
Andrea Parri <parri.andrea@gmail.com> Signed-off-by:
Peter Zijlstra (Intel) <peterz@infradead.org> 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: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by:
Ingo Molnar <mingo@kernel.org>
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- 23 Nov, 2015 1 commit
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Arnd Bergmann authored
The push_irq_work_func() function is conditionally defined only when both CONFIG_SMP and HAVE_RT_PUSH_IPI are defined, but the forward declaration remains visibile without HAVE_RT_PUSH_IPI, causing a gcc warning in ARM64 allnoconfig: kernel/sched/rt.c:68:13: warning: 'push_irq_work_func' declared 'static' but never defined [-Wunused-function] This changes the code to use the same condition for both the declaration and the function definition, which gets rid of the warning. As Peter Zijlstra, we can possibly get rid of the whole HAVE_RT_PUSH_IPI thing after: 8053871d ("smp: Fix smp_call_function_single_async() locking") Until that is done, this patch can be used to avoid the warning. Signed-off-by:
Arnd Bergmann <arnd@arndb.de> Signed-off-by:
Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by:
Steven Rostedt <rostedt@goodmis.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Fixes: b6366f04 ("sched/rt: Use IPI to trigger RT task push migration instead of pulling") Link: http://lkml.kernel.org/r/3828565.oKfGk7yNIT@wuerfelSigned-off-by:
Ingo Molnar <mingo@kernel.org>
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- 23 Sep, 2015 1 commit
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Juri Lelli authored
The return value of (do_)balance_runtime() is not consumed by anybody. Make them return void. 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/1441188096-23021-5-git-send-email-juri.lelli@arm.comSigned-off-by:
Ingo Molnar <mingo@kernel.org>
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- 12 Aug, 2015 2 commits
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Peter Zijlstra authored
Change the calling context of sched_class::set_cpus_allowed() such that we can assume the task is inactive. This allows us to easily make changes that affect accounting done by enqueue/dequeue. This does in fact completely remove set_cpus_allowed_rt() and greatly reduces set_cpus_allowed_dl(). 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/20150515154833.667516139@infradead.orgSigned-off-by:
Ingo Molnar <mingo@kernel.org>
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Peter Zijlstra authored
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.orgSigned-off-by:
Ingo Molnar <mingo@kernel.org>
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- 03 Aug, 2015 1 commit
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Xunlei Pang authored
'p' has been already queued at this point, so "!task_running(rq, p)" and "p->nr_cpus_allowed > 1" imply that "has_pushable_tasks(rq)" is true, so it can be removed. Signed-off-by:
Xunlei Pang <pang.xunlei@linaro.org> Signed-off-by:
Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by:
Steven Rostedt <rostedt@goodmis.org> Cc: Juri Lelli <juri.lelli@gmail.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> Link: http://lkml.kernel.org/r/1435995563-3723-1-git-send-email-xlpang@126.comSigned-off-by:
Ingo Molnar <mingo@kernel.org>
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- 18 Jun, 2015 4 commits
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Peter Zijlstra authored
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.orgSigned-off-by:
Thomas Gleixner <tglx@linutronix.de>
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Peter Zijlstra authored
Remove the direct {push,pull} balancing operations from switched_{from,to}_rt() / prio_changed_rt() and use the balance callback queue. Again, err on the side of too many reschedules; since too few is a hard bug while too many is just annoying. 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/20150611124742.766832367@infradead.orgSigned-off-by:
Thomas Gleixner <tglx@linutronix.de>
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Peter Zijlstra authored
In order to be able to use pull_rt_task() from a callback, we need to do away with the return value. Since the return value indicates if we should reschedule, do this inside the function. Since not all callers currently do this, this can increase the number of reschedules due rt balancing. Too many reschedules is not a correctness issues, too few are. 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/20150611124742.679002000@infradead.orgSigned-off-by:
Thomas Gleixner <tglx@linutronix.de>
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Peter Zijlstra authored
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.orgSigned-off-by:
Thomas Gleixner <tglx@linutronix.de>
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- 18 May, 2015 1 commit
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Peter Zijlstra authored
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: 272325c4 ("perf: Fix mux_interval hrtimer wreckage") Fixes: 77a4d1a1 ("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
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- 08 May, 2015 1 commit
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Jason Low authored
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.comSigned-off-by:
Ingo Molnar <mingo@kernel.org>
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- 22 Apr, 2015 1 commit
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Peter Zijlstra authored
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: 09dc4ab0 ("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.orgSigned-off-by:
Thomas Gleixner <tglx@linutronix.de>
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- 02 Apr, 2015 1 commit
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Abel Vesa authored
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.comSigned-off-by:
Ingo Molnar <mingo@kernel.org>
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- 23 Mar, 2015 1 commit
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Steven Rostedt authored
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.homeSigned-off-by:
Ingo Molnar <mingo@kernel.org>
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- 30 Jan, 2015 1 commit
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Tim Chen authored
This patch adds checks that prevens futile attempts to move rt tasks to a CPU with active tasks of equal or higher priority. This reduces run queue lock contention and improves the performance of a well known OLTP benchmark by 0.7%. Signed-off-by:
Tim Chen <tim.c.chen@linux.intel.com> Signed-off-by:
Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Shawn Bohrer <sbohrer@rgmadvisors.com> Cc: Suruchi Kadu <suruchi.a.kadu@intel.com> Cc: Doug Nelson<doug.nelson@intel.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/1421430374.2399.27.camel@schen9-desk2.jf.intel.comSigned-off-by:
Ingo Molnar <mingo@kernel.org>
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- 14 Jan, 2015 1 commit
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Peter Zijlstra authored
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.orgSigned-off-by:
Ingo Molnar <mingo@kernel.org>
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- 16 Nov, 2014 2 commits
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Wanpeng Li authored
Move the p->nr_cpus_allowed check into kernel/sched/core.c: select_task_rq(). This change will make fair.c, rt.c, and deadline.c all start with the same logic. Suggested-and-Acked-by:
Steven Rostedt <rostedt@goodmis.org> Signed-off-by:
Wanpeng Li <wanpeng.li@linux.intel.com> Signed-off-by:
Peter Zijlstra (Intel) <peterz@infradead.org> Cc: "pang.xunlei" <pang.xunlei@linaro.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/1415150077-59053-1-git-send-email-wanpeng.li@linux.intel.comSigned-off-by:
Ingo Molnar <mingo@kernel.org>
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Stanislaw Gruszka authored
Commit d670ec13 "posix-cpu-timers: Cure SMP wobbles" fixes one glibc test case in cost of breaking another one. After that commit, calling clock_nanosleep(TIMER_ABSTIME, X) and then clock_gettime(&Y) can result of Y time being smaller than X time. Reproducer/tester can be found further below, it can be compiled and ran by: gcc -o tst-cpuclock2 tst-cpuclock2.c -pthread while ./tst-cpuclock2 ; do : ; done This reproducer, when running on a buggy kernel, will complain about "clock_gettime difference too small". Issue happens because on start in thread_group_cputimer() we initialize sum_exec_runtime of cputimer with threads runtime not yet accounted and then add the threads runtime to running cputimer again on scheduler tick, making it's sum_exec_runtime bigger than actual threads runtime. KOSAKI Motohiro posted a fix for this problem, but that patch was never applied: https://lkml.org/lkml/2013/5/26/191 . This patch takes different approach to cure the problem. It calls update_curr() when cputimer starts, that assure we will have updated stats of running threads and on the next schedule tick we will account only the runtime that elapsed from cputimer start. That also assure we have consistent state between cpu times of individual threads and cpu time of the process consisted by those threads. Full reproducer (tst-cpuclock2.c): #define _GNU_SOURCE #include <unistd.h> #include <sys/syscall.h> #include <stdio.h> #include <time.h> #include <pthread.h> #include <stdint.h> #include <inttypes.h> /* Parameters for the Linux kernel ABI for CPU clocks. */ #define CPUCLOCK_SCHED 2 #define MAKE_PROCESS_CPUCLOCK(pid, clock) \ ((~(clockid_t) (pid) << 3) | (clockid_t) (clock)) static pthread_barrier_t barrier; /* Help advance the clock. */ static void *chew_cpu(void *arg) { pthread_barrier_wait(&barrier); while (1) ; return NULL; } /* Don't use the glibc wrapper. */ static int do_nanosleep(int flags, const struct timespec *req) { clockid_t clock_id = MAKE_PROCESS_CPUCLOCK(0, CPUCLOCK_SCHED); return syscall(SYS_clock_nanosleep, clock_id, flags, req, NULL); } static int64_t tsdiff(const struct timespec *before, const struct timespec *after) { int64_t before_i = before->tv_sec * 1000000000ULL + before->tv_nsec; int64_t after_i = after->tv_sec * 1000000000ULL + after->tv_nsec; return after_i - before_i; } int main(void) { int result = 0; pthread_t th; pthread_barrier_init(&barrier, NULL, 2); if (pthread_create(&th, NULL, chew_cpu, NULL) != 0) { perror("pthread_create"); return 1; } pthread_barrier_wait(&barrier); /* The test. */ struct timespec before, after, sleeptimeabs; int64_t sleepdiff, diffabs; const struct timespec sleeptime = {.tv_sec = 0,.tv_nsec = 100000000 }; /* The relative nanosleep. Not sure why this is needed, but its presence seems to make it easier to reproduce the problem. */ if (do_nanosleep(0, &sleeptime) != 0) { perror("clock_nanosleep"); return 1; } /* Get the current time. */ if (clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &before) < 0) { perror("clock_gettime[2]"); return 1; } /* Compute the absolute sleep time based on the current time. */ uint64_t nsec = before.tv_nsec + sleeptime.tv_nsec; sleeptimeabs.tv_sec = before.tv_sec + nsec / 1000000000; sleeptimeabs.tv_nsec = nsec % 1000000000; /* Sleep for the computed time. */ if (do_nanosleep(TIMER_ABSTIME, &sleeptimeabs) != 0) { perror("absolute clock_nanosleep"); return 1; } /* Get the time after the sleep. */ if (clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &after) < 0) { perror("clock_gettime[3]"); return 1; } /* The time after sleep should always be equal to or after the absolute sleep time passed to clock_nanosleep. */ sleepdiff = tsdiff(&sleeptimeabs, &after); if (sleepdiff < 0) { printf("absolute clock_nanosleep woke too early: %" PRId64 "\n", sleepdiff); result = 1; printf("Before %llu.%09llu\n", before.tv_sec, before.tv_nsec); printf("After %llu.%09llu\n", after.tv_sec, after.tv_nsec); printf("Sleep %llu.%09llu\n", sleeptimeabs.tv_sec, sleeptimeabs.tv_nsec); } /* The difference between the timestamps taken before and after the clock_nanosleep call should be equal to or more than the duration of the sleep. */ diffabs = tsdiff(&before, &after); if (diffabs < sleeptime.tv_nsec) { printf("clock_gettime difference too small: %" PRId64 "\n", diffabs); result = 1; } pthread_cancel(th); return result; } Signed-off-by:
Stanislaw Gruszka <sgruszka@redhat.com> Signed-off-by:
Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Rik van Riel <riel@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/20141112155843.GA24803@redhat.comSigned-off-by:
Ingo Molnar <mingo@kernel.org>
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- 04 Nov, 2014 1 commit
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Wanpeng Li authored
This patch checks if current can be pushed/pulled somewhere else in advance to make logic clear, the same behavior as dl class. - If current can't be migrated, useless to reschedule, let's hope task can move out. - If task is migratable, so let's not schedule it and see if it can be pushed or pulled somewhere else. Signed-off-by:
Wanpeng Li <wanpeng.li@linux.intel.com> Signed-off-by:
Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Juri Lelli <juri.lelli@arm.com> Cc: Kirill Tkhai <ktkhai@parallels.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/1414708776-124078-1-git-send-email-wanpeng.li@linux.intel.comSigned-off-by:
Ingo Molnar <mingo@kernel.org>
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- 24 Sep, 2014 1 commit
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Kirill Tkhai authored
Some time ago PREEMPT_NEED_RESCHED was implemented, so reschedule technics is a little more difficult now. Signed-off-by:
Kirill Tkhai <ktkhai@parallels.com> Signed-off-by:
Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/20140922183642.11015.66039.stgit@localhostSigned-off-by:
Ingo Molnar <mingo@kernel.org>
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- 19 Sep, 2014 1 commit
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Kirill Tkhai authored
_pick_next_task_rt() never returns NULL. Signed-off-by:
Kirill Tkhai <ktkhai@parallels.com> Signed-off-by:
Peter Zijlstra (Intel) <peterz@infradead.org> Link: http://lkml.kernel.org/r/1410529321.3569.26.camel@tkhai Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: linux-kernel@vger.kernel.org Signed-off-by:
Ingo Molnar <mingo@kernel.org>
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- 28 Aug, 2014 1 commit
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Christoph Lameter authored
__get_cpu_var can paper over differences in the definitions of cpumask_var_t and either use the address of the cpumask variable directly or perform a fetch of the address of the struct cpumask allocated elsewhere. This is important particularly when using per cpu cpumask_var_t declarations because in one case we have an offset into a per cpu area to handle and in the other case we need to fetch a pointer from the offset. This patch introduces a new macro this_cpu_cpumask_var_ptr() that is defined where cpumask_var_t is defined and performs the proper actions. All use cases where __get_cpu_var is used with cpumask_var_t are converted to the use of this_cpu_cpumask_var_ptr(). Signed-off-by:
Christoph Lameter <cl@linux.com> Signed-off-by:
Tejun Heo <tj@kernel.org>
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- 20 Aug, 2014 1 commit
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Kirill Tkhai authored
Implement task_on_rq_queued() and use it everywhere instead of on_rq check. No functional changes. The only exception is we do not use the wrapper in check_for_tasks(), because it requires to export task_on_rq_queued() in global header files. Next patch in series would return it back, so we do not twist it from here to there. Signed-off-by:
Kirill Tkhai <ktkhai@parallels.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Paul Turner <pjt@google.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Mike Galbraith <umgwanakikbuti@gmail.com> Cc: Kirill Tkhai <tkhai@yandex.ru> Cc: Tim Chen <tim.c.chen@linux.intel.com> Cc: Nicolas Pitre <nicolas.pitre@linaro.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/1408528052.23412.87.camel@tkhaiSigned-off-by:
Ingo Molnar <mingo@kernel.org>
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- 16 Jul, 2014 1 commit
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Kirill Tkhai authored
We always use resched_task() with rq->curr argument. It's not possible to reschedule any task but rq's current. The patch introduces resched_curr(struct rq *) to replace all of the repeating patterns. The main aim is cleanup, but there is a little size profit too: (before) $ size kernel/sched/built-in.o text data bss dec hex filename 155274 16445 7042 178761 2ba49 kernel/sched/built-in.o $ size vmlinux text data bss dec hex filename 7411490 1178376 991232 9581098 92322a vmlinux (after) $ size kernel/sched/built-in.o text data bss dec hex filename 155130 16445 7042 178617 2b9b9 kernel/sched/built-in.o $ size vmlinux text data bss dec hex filename 7411362 1178376 991232 9580970 9231aa vmlinux I was choosing between resched_curr() and resched_rq(), and the first name looks better for me. A little lie in Documentation/trace/ftrace.txt. I have not actually collected the tracing again. With a hope the patch won't make execution times much worse :) Signed-off-by:
Kirill Tkhai <tkhai@yandex.ru> Signed-off-by:
Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Link: http://lkml.kernel.org/r/20140628200219.1778.18735.stgit@localhostSigned-off-by:
Ingo Molnar <mingo@kernel.org>
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- 05 Jul, 2014 1 commit
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Kirill Tkhai authored
Make rt_rq available for pick_next_task(). Otherwise, their tasks stay prisoned long time till dead cpu becomes alive again. Reviewed-by:
Srikar Dronamraju <srikar@linux.vnet.ibm.com> Signed-off-by:
Kirill Tkhai <ktkhai@parallels.com> CC: Konstantin Khorenko <khorenko@parallels.com> CC: Ben Segall <bsegall@google.com> CC: Paul Turner <pjt@google.com> CC: Mike Galbraith <umgwanakikbuti@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by:
Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1403684388.3462.43.camel@tkhaiSigned-off-by:
Ingo Molnar <mingo@kernel.org>
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- 05 Jun, 2014 1 commit
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Giedrius Rekasius authored
Variable "rt_rq" is used only in block "for_each_sched_rt_entity" so the value assigned to it at the beginning of the update_curr_rt(...) gets overwritten without ever being read. Remove redundant assignment and move variable declaration to the block in which it is being used. Signed-off-by:
Giedrius Rekasius <giedrius.rekasius@gmail.com> Signed-off-by:
Peter Zijlstra <peterz@infradead.org> Cc: kernel-janitors@vger.kernel.org Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: linux-kernel@vger.kernel.org Link: http://lkml.kernel.org/r/1401027811-30066-1-git-send-email-giedrius.rekasius@gmail.comSigned-off-by:
Ingo Molnar <mingo@kernel.org>
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- 04 Jun, 2014 2 commits
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John Stultz authored
Two of the three prink_deferred uses are really printk_once style uses, so add a printk_deferred_once macro to simplify those call sites. Signed-off-by:
John Stultz <john.stultz@linaro.org> Reviewed-by:
Steven Rostedt <rostedt@goodmis.org> Reviewed-by:
Jan Kara <jack@suse.cz> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Jiri Bohac <jbohac@suse.cz> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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John Stultz authored
After learning we'll need some sort of deferred printk functionality in the timekeeping core, Peter suggested we rename the printk_sched function so it can be reused by needed subsystems. This only changes the function name. No logic changes. Signed-off-by:
John Stultz <john.stultz@linaro.org> Reviewed-by:
Steven Rostedt <rostedt@goodmis.org> Cc: Jan Kara <jack@suse.cz> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Jiri Bohac <jbohac@suse.cz> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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