- 15 Jun, 2020 40 commits
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Peter Zijlstra authored
Because SCHED_FIFO is a broken scheduler model (see previous patches) take away the priority field, the kernel can't possibly make an informed decision. Effectively no change. Cc: paulmck@kernel.org Signed-off-by:
Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by:
Ingo Molnar <mingo@kernel.org> Reviewed-by:
Paul E. McKenney <paulmck@kernel.org>
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Peter Zijlstra authored
Because SCHED_FIFO is a broken scheduler model (see previous patches) take away the priority field, the kernel can't possibly make an informed decision. Effectively changes prio from 99 to 50. Cc: paulmck@kernel.org Signed-off-by:
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Peter Zijlstra authored
Because SCHED_FIFO is a broken scheduler model (see previous patches) take away the priority field, the kernel can't possibly make an informed decision. Effectively no change. Cc: tglx@linutronix.de Signed-off-by:
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Peter Zijlstra authored
Because SCHED_FIFO is a broken scheduler model (see previous patches) take away the priority field, the kernel can't possibly make an informed decision. Effectively changes prio from 99 to 50. Cc: wim@linux-watchdog.org Signed-off-by:
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Peter Zijlstra authored
Because SCHED_FIFO is a broken scheduler model (see previous patches) take away the priority field, the kernel can't possibly make an informed decision. Effectively no change. Signed-off-by:
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Peter Zijlstra authored
Because SCHED_FIFO is a broken scheduler model (see previous patches) take away the priority field, the kernel can't possibly make an informed decision. Effectively no change. Cc: rafael.j.wysocki@intel.com Signed-off-by:
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Peter Zijlstra authored
In an attempt to take away sched_setscheduler() from modules, change this into sched_set_normal(.nice = 19). Cc: john.stultz@linaro.org Signed-off-by:
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Peter Zijlstra authored
Because SCHED_FIFO is a broken scheduler model (see previous patches) take away the priority field, the kernel can't possibly make an informed decision. Effectively no change. Cc: daniel.lezcano@linaro.org Cc: rafael.j.wysocki@intel.com Signed-off-by:
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Peter Zijlstra authored
Because SCHED_FIFO is a broken scheduler model (see previous patches) take away the priority field, the kernel can't possibly make an informed decision. No effective change. Cc: broonie@kernel.org Signed-off-by:
Douglas Anderson <dianders@chromium.org> Reviewed-by:
Guenter Roeck <groeck@chromium.org>
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Peter Zijlstra authored
Because SCHED_FIFO is a broken scheduler model (see previous patches) take away the priority field, the kernel can't possibly make an informed decision. In this case, use fifo_low, because it only cares about being above SCHED_NORMAL. Effectively no change in behaviour. Signed-off-by:
Ulf Hansson <ulf.hansson@linaro.org>
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Peter Zijlstra authored
Because SCHED_FIFO is a broken scheduler model (see previous patches) take away the priority field, the kernel can't possibly make an informed decision. Effectively changes from 99 to 50. Cc: awalls@md.metrocast.net Signed-off-by:
Hans Verkuil <hverkuil-cisco@xs4all.nl> Tested-by:
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Peter Zijlstra authored
Because SCHED_FIFO is a broken scheduler model (see previous patches) take away the priority field, the kernel can't possibly make an informed decision. In this case, use fifo_low, because it only cares about being above SCHED_NORMAL. Effectively no change in behaviour. Cc: alexander.deucher@amd.com Signed-off-by:
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Peter Zijlstra authored
Because SCHED_FIFO is a broken scheduler model (see previous patches) take away the priority field, the kernel can't possibly make an informed decision. Use sched_set_fifo(); Effectively changes prio from 16 to 50. Cc: airlied@redhat.com Signed-off-by:
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Peter Zijlstra authored
Because SCHED_FIFO is a broken scheduler model (see previous patches) take away the priority field, the kernel can't possibly make an informed decision. Effectively changes prio from 99 to 50. XXX this thing is horrific, it basically open-codes a stop-machine and idle. Cc: daniel.lezcano@linaro.org Signed-off-by:
Valentin Schneider <valentin.schneider@arm.com> Tested-by:
Sudeep Holla <sudeep.holla@arm.com>
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Peter Zijlstra authored
Because SCHED_FIFO is a broken scheduler model (see previous patches) take away the priority field, the kernel can't possibly make an informed decision. In this case, use fifo_low, because it only cares about being above SCHED_NORMAL. Effectively changes prio from 2 to 1. Cc: axboe@kernel.dk Signed-off-by:
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Peter Zijlstra authored
Because SCHED_FIFO is a broken scheduler model (see previous patches) take away the priority field, the kernel can't possibly make an informed decision. In this case, use fifo_low, because it only cares about being above SCHED_NORMAL. Effectively no change in behaviour. XXX: this driver is still complete crap; why isn't it using proper idle injection or at the very least play_idle() ? Cc: rafael.j.wysocki@intel.com Signed-off-by:
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Peter Zijlstra authored
Because SCHED_FIFO is a broken scheduler model (see previous patches) take away the priority field, the kernel can't possibly make an informed decision. Use sched_set_fifo() to request SCHED_FIFO and delegate actual priority selection to userspace. Effectively no change in behaviour. Signed-off-by:
Herbert Xu <herbert@gondor.apana.org.au>
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Peter Zijlstra authored
Because SCHED_FIFO is a broken scheduler model (see previous patches) take away the priority field, the kernel can't possibly make an informed decision. In this case, use fifo_low, because it only cares about being above SCHED_NORMAL. Effectively no change in behaviour. Cc: rmk+kernel@arm.linux.org.uk Signed-off-by:
Nicolas Pitre <nico@fluxnic.net>
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Peter Zijlstra authored
SCHED_FIFO (or any static priority scheduler) is a broken scheduler model; it is fundamentally incapable of resource management, the one thing an OS is actually supposed to do. It is impossible to compose static priority workloads. One cannot take two well designed and functional static priority workloads and mash them together and still expect them to work. Therefore it doesn't make sense to expose the priority field; the kernel is fundamentally incapable of setting a sensible value, it needs systems knowledge that it doesn't have. Take away sched_setschedule() / sched_setattr() from modules and replace them with: - sched_set_fifo(p); create a FIFO task (at prio 50) - sched_set_fifo_low(p); create a task higher than NORMAL, which ends up being a FIFO task at prio 1. - sched_set_normal(p, nice); (re)set the task to normal This stops the proliferation of randomly chosen, and irrelevant, FIFO priorities that dont't really mean anything anyway. The system administrator/integrator, whoever has insight into the actual system design and requirements (userspace) can set-up appropriate priorities if and when needed. Cc: airlied@redhat.com Cc: alexander.deucher@amd.com Cc: awalls@md.metrocast.net Cc: axboe@kernel.dk Cc: broonie@kernel.org Cc: daniel.lezcano@linaro.org Cc: gregkh@linuxfoundation.org Cc: hannes@cmpxchg.org Cc: herbert@gondor.apana.org.au Cc: hverkuil@xs4all.nl Cc: john.stultz@linaro.org Cc: nico@fluxnic.net Cc: paulmck@kernel.org Cc: rafael.j.wysocki@intel.com Cc: rmk+kernel@arm.linux.org.uk Cc: sudeep.holla@arm.com Cc: tglx@linutronix.de Cc: ulf.hansson@linaro.org Cc: wim@linux-watchdog.org Signed-off-by:
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Vincent Guittot authored
Factorize in a single place the calculation of the divider to be used to to compute *_avg from *_sum value Suggested-by:
Dietmar Eggemann <dietmar.eggemann@arm.com> Signed-off-by:
Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by:
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Christophe JAILLET authored
s/deadine/deadline/ Signed-off-by:
Christophe JAILLET <christophe.jaillet@wanadoo.fr> Signed-off-by:
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Luca Abeni authored
When a task has a runtime that cannot be served within the scheduling deadline by any of the idle CPU (later_mask) the task is doomed to miss its deadline. This can happen since the SCHED_DEADLINE admission control guarantees only bounded tardiness and not the hard respect of all deadlines. In this case try to select the idle CPU with the largest CPU capacity to minimize tardiness. Favor task_cpu(p) if it has max capacity of !fitting CPUs so that find_later_rq() can potentially still return it (most likely cache-hot) early. Signed-off-by:
Luca Abeni <luca.abeni@santannapisa.it> Signed-off-by:
Juri Lelli <juri.lelli@redhat.com> Link: https://lkml.kernel.org/r/20200520134243.19352-6-dietmar.eggemann@arm.com
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Luca Abeni authored
The current SCHED_DEADLINE (DL) scheduler uses a global EDF scheduling algorithm w/o considering CPU capacity or task utilization. This works well on homogeneous systems where DL tasks are guaranteed to have a bounded tardiness but presents issues on heterogeneous systems. A DL task can migrate to a CPU which does not have enough CPU capacity to correctly serve the task (e.g. a task w/ 70ms runtime and 100ms period on a CPU w/ 512 capacity). Add the DL fitness function dl_task_fits_capacity() for DL admission control on heterogeneous systems. A task fits onto a CPU if: CPU original capacity / 1024 >= task runtime / task deadline Use this function on heterogeneous systems to try to find a CPU which meets this criterion during task wakeup, push and offline migration. On homogeneous systems the original behavior of the DL admission control should be retained. Signed-off-by: -
Luca Abeni authored
The current SCHED_DEADLINE (DL) admission control ensures that sum of reserved CPU bandwidth < x * M where x = /proc/sys/kernel/sched_rt_{runtime,period}_us M = # CPUs in root domain. DL admission control works well for homogeneous systems where the capacity of all CPUs are equal (1024). I.e. bounded tardiness for DL and non-starvation of non-DL tasks is guaranteed. But on heterogeneous systems where capacity of CPUs are different it could fail by over-allocating CPU time on smaller capacity CPUs. On an Arm big.LITTLE/DynamIQ system DL tasks can easily starve other tasks making it unusable. Fix this by explicitly considering the CPU capacity in the DL admission test by replacing M with the root domain CPU capacity sum. Signed-off-by: -
Dietmar Eggemann authored
Capacity-aware SCHED_DEADLINE Admission Control (AC) needs root domain (rd) CPU capacity sum. Introduce dl_bw_capacity() which for a symmetric rd w/ a CPU capacity of SCHED_CAPACITY_SCALE simply relies on dl_bw_cpus() to return #CPUs multiplied by SCHED_CAPACITY_SCALE. For an asymmetric rd or a CPU capacity < SCHED_CAPACITY_SCALE it computes the CPU capacity sum over rd span and cpu_active_mask. A 'XXX Fix:' comment was added to highlight that if 'rq->rd == def_root_domain' AC should be performed against the capacity of the CPU the task is running on rather the rd CPU capacity sum. This issue already exists w/o capacity awareness. Signed-off-by:
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Dietmar Eggemann authored
Return the weight of the root domain (rd) span in case it is a subset of the cpu_active_mask. Continue to compute the number of CPUs over rd span and cpu_active_mask when in hotplug. Signed-off-by:
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Peng Liu authored
During sched domain init, we check whether non-topological SD_flags are returned by tl->sd_flags(), if found, fire a waning and correct the violation, but the code failed to correct the violation. Correct this. Fixes: 143e1e28 ("sched: Rework sched_domain topology definition") Signed-off-by:
Peng Liu <iwtbavbm@gmail.com> Signed-off-by:
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Vincent Guittot authored
With commit: 'b7031a02 ("sched/fair: Add NOHZ_STATS_KICK")' rebalance_domains of the local cfs_rq happens before others idle cpus have updated nohz.next_balance and its value is overwritten. Move the update of nohz.next_balance for other idles cpus before balancing and updating the next_balance of local cfs_rq. Also, the nohz.next_balance is now updated only if all idle cpus got a chance to rebalance their domains and the idle balance has not been aborted because of new activities on the CPU. In case of need_resched, the idle load balance will be kick the next jiffie in order to address remaining ilb. Fixes: b7031a02 ("sched/fair: Add NOHZ_STATS_KICK") Reported-by:
Mel Gorman <mgorman@suse.de> Link: https://lkml.kernel.org/r/20200609123748.18636-1-vincent.guittot@linaro.org
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Peter Zijlstra authored
Signed-off-by:
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Marcelo Tosatti authored
This is a kernel enhancement that configures the cpu affinity of kernel threads via kernel boot option nohz_full=. When this option is specified, the cpumask is immediately applied upon kthread launch. This does not affect kernel threads that specify cpu and node. This allows CPU isolation (that is not allowing certain threads to execute on certain CPUs) without using the isolcpus=domain parameter, making it possible to enable load balancing on such CPUs during runtime (see kernel-parameters.txt). Note-1: this is based off on Wind River's patch at https://github.com/starlingx-staging/stx-integ/blob/master/kernel/kernel-std/centos/patches/affine-compute-kernel-threads.patch Difference being that this patch is limited to modifying kernel thread cpumask. Behaviour of other threads can be controlled via cgroups or sched_setaffinity. Note-2: Wind River's patch was based off Christoph Lameter's patch at https://lwn.net/Articles/565932/ with the only difference being the kernel parameter changed from kthread to kthread_cpus. Signed-off-by:
Frederic Weisbecker <frederic@kernel.org> Signed-off-by:
Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by:
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Marcelo Tosatti authored
Next patch will switch unbound kernel threads mask to housekeeping_cpumask(), a subset of cpu_possible_mask. So in order to ease bisection, lets first switch kthreads default affinity from cpu_all_mask to cpu_possible_mask. It looks safe to do so as cpu_possible_mask seem to be initialized at setup_arch() time, way before kthreadd is created. Suggested-by:
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Suren Baghdasaryan authored
Each psi group requires a dedicated kthread_delayed_work and kthread_worker. Since no other work can be performed using psi_group's kthread_worker, the same result can be obtained using a task_struct and a timer directly. This makes psi triggering simpler by removing lists and locks involved with kthread_worker usage and eliminates the need for poll_scheduled atomic use in the hot path. Signed-off-by:
Suren Baghdasaryan <surenb@google.com> Signed-off-by:
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Giovanni Gherdovich authored
Be defensive against the case where the processor reports a base_freq larger than turbo_freq (the ratio would be zero). Fixes: 1567c3e3 ("x86, sched: Add support for frequency invariance") Signed-off-by:
Giovanni Gherdovich <ggherdovich@suse.cz> Signed-off-by:
Rafael J. Wysocki <rafael.j.wysocki@intel.com> Link: https://lkml.kernel.org/r/20200531182453.15254-4-ggherdovich@suse.cz
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Giovanni Gherdovich authored
There may be CPUs that support turbo boost but don't declare any turbo ratio, i.e. their MSR_TURBO_RATIO_LIMIT is all zeroes. In that condition scale-invariant calculations can't be performed. Fixes: 1567c3e3 ("x86, sched: Add support for frequency invariance") Suggested-by:
Ricardo Neri <ricardo.neri-calderon@linux.intel.com> Signed-off-by:
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Giovanni Gherdovich authored
The product mcnt * arch_max_freq_ratio can overflows u64. For context, a large value for arch_max_freq_ratio would be 5000, corresponding to a turbo_freq/base_freq ratio of 5 (normally it's more like 1500-2000). A large increment frequency for the MPERF counter would be 5GHz (the base clock of all CPUs on the market today is less than that). With these figures, a CPU would need to go without a scheduler tick for around 8 days for the u64 overflow to happen. It is unlikely, but the check is warranted. Under similar conditions, the difference acnt of two consecutive APERF readings can overflow as well. In these circumstances is appropriate to disable frequency invariant accounting: the feature relies on measures of the clock frequency done at every scheduler tick, which need to be "fresh" to be at all meaningful. A note on i386: prior to version 5.1, the GCC compiler didn't have the builtin function __builtin_mul_overflow. In these GCC versions the macro check_mul_overflow needs __udivdi3() to do (u64)a/b, which the kernel doesn't provide. For this reason this change fails to build on i386 if GCC<5.1, and we protect the entire frequency invariant code behind CONFIG_X86_64 (special thanks to "kbuild test robot" <lkp@intel.com>). Fixes: 1567c3e3 ("x86, sched: Add support for frequency invariance") Signed-off-by:
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Vincent Donnefort authored
The util_est signals are key elements for EAS task placement and frequency selection. Having tracepoints to track these signals enables load-tracking and schedutil testing and/or debugging by a toolkit. Signed-off-by:
Vincent Donnefort <vincent.donnefort@arm.com> Signed-off-by:
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Dietmar Eggemann authored
Since commit 8ec59c0f ("sched/topology: Remove unused 'sd' parameter from arch_scale_cpu_capacity()") it is no longer needed. Signed-off-by:
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Dietmar Eggemann authored
The idle task and stop task sched_classes return 0 in this function. The single call site in sched_rr_get_interval() calls p->sched_class->get_rr_interval() only conditional in case it is defined. Otherwise time_slice=0 will be used. The deadline sched class does not define it. Commit a57beec5 ("sched: Make sched_class::get_rr_interval() optional") introduced the default time-slice=0 for sched classes which do not provide this function. So .get_rr_interval for idle and stop sched_class can be removed to shrink the code a little. Signed-off-by:
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Dietmar Eggemann authored
Commit 6d1cafd8 ("sched: Resched proper CPU on yield_to()") moved the code to resched the CPU from yield_to_task_fair() to yield_to() making the preempt parameter in sched_class->yield_to_task() unnecessary. Remove it. No other sched_class implements yield_to_task(). Signed-off-by:
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Dietmar Eggemann authored
Besides in PELT cap_scale() is used in the Deadline scheduler class for scale-invariant bandwidth enforcement. Remove the cap_scale() definition in kernel/sched/pelt.c and keep the one in kernel/sched/sched.h. Signed-off-by:
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