eas-dev April 2017

eas-dev@lists.linaro.org

4 participants
3 discussions

[RFC 0/9] cpufreq: schedutil: Allow remote wakeups

by Viresh Kumar

Hi, This is based of the work done by Steve Muckle [1] before he left Linaro and most of the patches are still under his authorship. I have done couple of improvements (detailed in individual patches) and removed the late callback support [2] as I wasn't sure of the value it adds. We can include it separately if others feel it is required. This series is based on pm/linux-next with patches [3] and [4] applied on top of it. With Android UI and benchmarks the latency of cpufreq response to certain scheduling events can become very critical. Currently, callbacks into schedutil are only made from the scheduler if the target CPU of the event is the same as the current CPU. This means there are certain situations where a target CPU may not run schedutil for some time. One testcase to show this behavior is where a task starts running on CPU0, then a new task is also spawned on CPU0 by a task on CPU1. If the system is configured such that new tasks should receive maximum demand initially, this should result in CPU0 increasing frequency immediately. Because of the above mentioned limitation though this does not occur. This is verified using ftrace with the sample [5] application. This patchset updates the scheduler to call cpufreq callbacks for remote CPUs as well and updates schedutil governor to deal with it. An additional flag is added to cpufreq policies to avoid sending IPIs to remote CPUs to update the frequency, if CPUs on the platform can change frequency of any other CPU. This series is tested with couple of usecases (Android: hackbench, recentfling, galleryfling, vellamo, Ubuntu: hackbench) on ARM hikey board (64 bit octa-core, single policy). Only galleryfling showed minor improvements, while others didn't had much deviation. The reason being that this patchset only targets a corner case, where following are required to be true to improve performance and that doesn't happen too often with these tests: - Task is migrated to another CPU. - The task has maximum demand initially, and should take the CPU to higher OPPs. - And the target CPU doesn't call into schedutil until the next tick, without this patchset. -- viresh [1] https://git.linaro.org/people/steve.muckle/kernel.git/log/?h=pmwg-integrati… [2] https://git.linaro.org/people/steve.muckle/kernel.git/commit/?h=pmwg-integr… [3] https://marc.info/?l=linux-kernel&m=148766093718487&w=2 [4] https://marc.info/?l=linux-kernel&m=148903231720432&w=2 [5] http://pastebin.com/7LkMSRxE Steve Muckle (8): sched: cpufreq: add cpu to update_util_data irq_work: add irq_work_queue_on for !CONFIG_SMP sched: cpufreq: extend irq work to support fast switches sched: cpufreq: remove smp_processor_id() in remote paths sched: cpufreq: detect, process remote callbacks cpufreq: governor: support scheduler cpufreq callbacks on remote CPUs intel_pstate: ignore scheduler cpufreq callbacks on remote CPUs sched: cpufreq: enable remote sched cpufreq callbacks Viresh Kumar (1): cpufreq: Add dvfs_possible_from_any_cpu policy flag drivers/cpufreq/cpufreq-dt.c | 1 + drivers/cpufreq/cpufreq_governor.c | 2 +- drivers/cpufreq/intel_pstate.c | 3 ++ include/linux/cpufreq.h | 9 +++++ include/linux/irq_work.h | 7 ++++ include/linux/sched/cpufreq.h | 1 + kernel/sched/cpufreq.c | 1 + kernel/sched/cpufreq_schedutil.c | 80 +++++++++++++++++++++++++++++--------- kernel/sched/fair.c | 6 ++- kernel/sched/sched.h | 3 +- 10 files changed, 90 insertions(+), 23 deletions(-) -- 2.7.1.410.g6faf27b

7 years, 1 month

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by USPS Parcels Delivery

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7 years, 1 month

[ANNOUNCE] OSPM-summit is on next Monday

by Juri Lelli

Hi, we are only a week away from the OSPM-summit! Pack your bags (or stay tuned for the live streaming). Don't forget to subscribe to the summit mailing list to receive updates by either following the instructions available at the following link http://groups.google.com/group/ospm-summit-2017/boxsubscribe?email=<your_email> or sending an email to ospm-summit-2017+subscribe(a)googlegroups.com Archives are available at https://groups.google.com/forum/#!forum/ospm-summit-2017 More information about schedule and logistics follow. --- Power Management and Scheduling in the Linux Kernel (OSPM-summit) April 3-4, 2017 Scuola Superiore Sant'Anna (SSSA) Pisa, Italy http://retis.sssup.it/ospm-summit/ --- .:: FOCUS Power management and scheduling techniques to reduce energy consumption while meeting performance and latency requirements are receiving considerable attention from the Linux Kernel development community. The Power Management and Scheduling in the Linux Kernel (OSPM-summit) summit aims at fostering further interest and discussion to happen. .:: SCHEDULE The summit is organized to cover two days of discussions and talks. What follows is a tentative schedule, subject to last minute changes. Find more info and real time updates on this shared document: https://docs.google.com/spreadsheets/d/1B-IsUIGitvRa7ZzppEAJBMgGpIgRAAnu_Oh… Monday (2017-04-03) ******************* 09:00AM - 09:30AM Welcome and Introduction (DAY 1) --- 09:30AM - 10:20AM Tooling/LISA --- 10:20AM - 11:10AM About The Need to Power Instrument The Linux Kernel --- 11:10AM - 11:20AM Break --- 11:20AM - 12:10AM What are the latest evolutions in PELT and what next --- 12:10AM - 01:00PM PELT decay clamping/UTIL_EST --- 01:00PM - 02:30PM Lunch --- 02:30PM - 03:20PM EAS where we are --- 03:20PM - 04:10PM Energy model/Exotic topologies --- 04:10PM - 04:20PM Break --- 04:20PM - 05:10PM Schedtune --- 05:10PM - 06:00PM SCHED_DEADLINE and reclaiming Tuesday (2017-04-04) ******************** 09:00AM - 09:30AM Welcome and Introduction (DAY 2) --- 09:30AM - 10:20AM Discussion about possible improvements in the schedutil governor --- 10:20AM - 11:10AM Schedutil for SCHED_DEADLINE --- 11:10AM - 11:20AM Break --- 11:20AM - 12:10AM Parameterizing CFS load balancing: nr_running/util/load --- 12:10AM - 01:00PM Tracepoints for PELT --- 01:00PM - 02:30PM Lunch --- 02:30PM - 03:20PM IRQ prediction --- 03:20PM - 04:10PM I/O scheduling and power management with storage devices --- 04:10PM - 04:20PM Break --- 04:20PM - 05:10PM SCHED_DEADLINE group scheduling --- 05:10PM - 06:00PM A Hierarchical Scheduling Model for Dynamic Soft-Realtime Systems --- 06:00PM - 06:30PM Closing Remarks We are looking into setting up live streaming of the sessions. Details will be soon shared through the shared doc mentioned above and the event mailing list. List of attendees is also available in the doc and on the event website. .:: VENUE The workshop will take place at ReTiS Lab*, Scuola Superiore Sant'Anna, Pisa, Italy. Pisa is a small town, walking distance from the city center to the venue is 20 minutes, walking distance from the airport to the city center is 30 minutes. More details are available from the summit web page: http://retis.sssup.it/ospm-summit/ A map of the town with venue location, points of interest and transportation information is available at: https://drive.google.com/open?id=1ANKOXr2cuZkABXskDurgrGdl_js&usp=sharing Bus from Airport to city centre takes about 10 min and costs 1.20 euros (2 euros if bought on board). Large bills are usually not accepted. Taxi from Airport to city centre costs 10/15 euros. Credit cards are not accepted. .:: ORGANIZERS (in alphabetical order) Luca Abeni (SSSA) Patrick Bellasi (ARM) Tommaso Cucinotta (SSSA) Dietmar Eggemann (ARM) Sudeep Holla (ARM) Juri Lelli (ARM) Lorenzo Pieralisi (ARM) Morten Rasmussen (ARM)

7 years, 2 months

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eas-dev April 2017