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5b77261c |
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09-Oct-2023 |
Pierre Gondois <Pierre.Gondois@arm.com> |
sched/topology: Remove the EM_MAX_COMPLEXITY limit The Energy Aware Scheduler (EAS) estimates the energy consumption of placing a task on different CPUs. The goal is to minimize this energy consumption. Estimating the energy of different task placements is increasingly complex with the size of the platform. To avoid having a slow wake-up path, EAS is only enabled if this complexity is low enough. The current complexity limit was set in: b68a4c0dba3b1 ("sched/topology: Disable EAS on inappropriate platforms") ... based on the first implementation of EAS, which was re-computing the power of the whole platform for each task placement scenario, see: 390031e4c309 ("sched/fair: Introduce an energy estimation helper function") ... but the complexity of EAS was reduced in: eb92692b2544d ("sched/fair: Speed-up energy-aware wake-ups") ... and find_energy_efficient_cpu() (feec) algorithm was updated in: 3e8c6c9aac42 ("sched/fair: Remove task_util from effective utilization in feec()") find_energy_efficient_cpu() (feec) is now doing: feec() \_ for_each_pd(pd) [0] // get max_spare_cap_cpu and compute_prev_delta \_ for_each_cpu(pd) [1] \_ eenv_pd_busy_time(pd) [2] \_ for_each_cpu(pd) // compute_energy(pd) without the task \_ eenv_pd_max_util(pd, -1) [3.0] \_ for_each_cpu(pd) \_ em_cpu_energy(pd, -1) \_ for_each_ps(pd) // compute_energy(pd) with the task on prev_cpu \_ eenv_pd_max_util(pd, prev_cpu) [3.1] \_ for_each_cpu(pd) \_ em_cpu_energy(pd, prev_cpu) \_ for_each_ps(pd) // compute_energy(pd) with the task on max_spare_cap_cpu \_ eenv_pd_max_util(pd, max_spare_cap_cpu) [3.2] \_ for_each_cpu(pd) \_ em_cpu_energy(pd, max_spare_cap_cpu) \_ for_each_ps(pd) [3.1] happens only once since prev_cpu is unique. With the same definitions for nr_pd, nr_cpus and nr_ps, the complexity is of: nr_pd * (2 * [nr_cpus in pd] + 2 * ([nr_cpus in pd] + [nr_ps in pd])) + ([nr_cpus in pd] + [nr_ps in pd]) [0] * ( [1] + [2] + [3.0] + [3.2] ) + [3.1] = nr_pd * (4 * [nr_cpus in pd] + 2 * [nr_ps in pd]) + [nr_cpus in prev pd] + nr_ps The complexity limit was set to 2048 in: b68a4c0dba3b1 ("sched/topology: Disable EAS on inappropriate platforms") ... to make "EAS usable up to 16 CPUs with per-CPU DVFS and less than 8 performance states each". For the same platform, the complexity would actually be of: 16 * (4 + 2 * 7) + 1 + 7 = 296 Since the EAS complexity was greatly reduced since the limit was introduced, bigger platforms can handle EAS. For instance, a platform with 112 CPUs with 7 performance states each would not reach it: 112 * (4 + 2 * 7) + 1 + 7 = 2024 To reflect this improvement in the underlying EAS code, remove the EAS complexity check. Note that a limit on the number of CPUs still holds against EM_MAX_NUM_CPUS to avoid overflows during the energy estimation. [ mingo: Updates to the changelog. ] Signed-off-by: Pierre Gondois <Pierre.Gondois@arm.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Lukasz Luba <lukasz.luba@arm.com> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Link: https://lore.kernel.org/r/20231009060037.170765-2-sshegde@linux.vnet.ibm.com
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d56b699d |
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14-Aug-2023 |
Bjorn Helgaas <bhelgaas@google.com> |
Documentation: Fix typos Fix typos in Documentation. Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Link: https://lore.kernel.org/r/20230814212822.193684-4-helgaas@kernel.org Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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adf3c31e |
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03-Jun-2021 |
Beata Michalska <beata.michalska@arm.com> |
sched/doc: Update the CPU capacity asymmetry bits Update the documentation bits referring to capacity aware scheduling with regards to newly introduced SD_ASYM_CPUCAPACITY_FULL sched_domain flag. Signed-off-by: Beata Michalska <beata.michalska@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Valentin Schneider <valentin.schneider@arm.com> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Link: https://lore.kernel.org/r/20210603140627.8409-4-beata.michalska@arm.com
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5a64f775 |
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03-Nov-2020 |
Lukasz Luba <lukasz.luba@arm.com> |
PM: EM: Clarify abstract scale usage for power values in Energy Model The Energy Model (EM) can store power values in milli-Watts or in abstract scale. This might cause issues in the subsystems which use the EM for estimating the device power, such as: - mixing of different scales in a subsystem which uses multiple (cooling) devices (e.g. thermal Intelligent Power Allocation (IPA)) - assuming that energy [milli-Joules] can be derived from the EM power values which might not be possible since the power scale doesn't have to be in milli-Watts To avoid misconfiguration add the requisite documentation to the EM and related subsystems: EAS and IPA. Signed-off-by: Lukasz Luba <lukasz.luba@arm.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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e4e29e78 |
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09-Sep-2020 |
Mauro Carvalho Chehab <mchehab+huawei@kernel.org> |
docs: scheduler: fix the directory name on two files The name of the directory where the schedule docs are stored are wrong on those files. Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Reviewed-by: Valentin Schneider <valentin.schneider@arm.com> Link: https://lore.kernel.org/r/a32c2bba17aa69dc18670b7de1a3a35bfa1e1f88.1599660067.git.mchehab+huawei@kernel.org Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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949bcb81 |
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31-Jul-2020 |
Valentin Schneider <valentin.schneider@arm.com> |
sched/doc: Factorize bits between sched-energy.rst & sched-capacity.rst Documentation/scheduler/sched-capacity.rst ought to be the canonical place to blabber about SD_ASYM_CPUCAPACITY, so remove its explanation from sched-energy.rst and point to sched-capacity.rst instead. Signed-off-by: Valentin Schneider <valentin.schneider@arm.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/20200731192016.7484-4-valentin.schneider@arm.com
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d6a3b247 |
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12-Jun-2019 |
Mauro Carvalho Chehab <mchehab+samsung@kernel.org> |
docs: scheduler: convert docs to ReST and rename to *.rst In order to prepare to add them to the Kernel API book, convert the files to ReST format. The conversion is actually: - add blank lines and identation in order to identify paragraphs; - fix tables markups; - add some lists markups; - mark literal blocks; - adjust title markups. At its new index.rst, let's add a :orphan: while this is not linked to the main index.rst file, in order to avoid build warnings. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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