Hi, this RFC set implements frequency/cpu invariance and OPP selection for SCHED_DEADLINE. The set has been slightly tested on a Juno platform. The current incarnation of the patches stems both from previous RFD[1] review comments and discussion at OSPM-summit[2], during which we seemed to agree that:
- we probably want to use running_bw (instead of this_bw), as it is less pessimistic (we should save more energy) - special kworker hack seems acceptable as a mid term solution to foster further SCHED_DEADLINE/schedutil development/adoption A point that is still very much up for discussion (more that the others :) is how we implement frequency/cpu scaling. SCHED_FLAG_RECLAIM tasks only need grub_reclaim(), as the function already scales their reservation runtime considering other reservations and maximum bandwidth a CPU has to offer. However, for normal !RECLAIM tasks multiple things can be implemented which seem to make sense: - don't scale at all: normal tasks will only get a % of CPU _time_ as granted by AC - go to max as soon as a normal task in enqueued: this because dimensioning of parameters is usually done at max OPP/biggest CPU and normal task assume that this is always the condition when they run - scale runtime acconding to current frequency and max CPU capacity: this is what this set is currently implementing Opinions? The set is based on tip/sched/core as of today (a9e7f6544b9c) plus some schedutil fixes coming from linux-pm/linux-next and Luca's "CPU reclaiming for SCHED_DEADLINE" [3]. Patches high level description: o [01-02]/08 add the necessary links to start accounting DEADLINE contribution to OPP selection o 03/08 it's a temporary solution to make possible (on ARM) to change frequency for DEADLINE tasks (that would possibly delay the SCHED_FIFO worker kthread); proper solution would be to be able to issue frequency transition from an atomic ctx o [04-05]/08 it's a schedutil change that copes with the fact that DEADLINE doesn't require periodic OPP selection triggering point o [06-07]/08 make arch_scale_{freq,cpu}_capacity() function available on !CONFIG_SMP configurations too o 08/08 implements frequency/cpu invariance for tasks' reservation parameters; which basically means that we implement GRUB-PA [4] Changes w.r.t. RFD: - use grub_reclaim for RECLAIM and scale freq/cpu for !RECLAIM - discard CFS contribution only, after TICK_NSEC - added patches 06 and 07 to fix !CONFIG_SMP builds Please have a look. Feedback and comments are, as usual, more than welcome. In case you would like to test this out: git://linux-arm.org/linux-jl.git upstream/deadline/freq-rfc Best, - Juri [1] http://marc.info/?l=linux-kernel&m=149036457909119&w=2 [2] http://retis.sssup.it/ospm-summit/program.html https://lwn.net/Articles/721573/ [3] http://marc.info/?l=linux-kernel&m=149513848804404 [4] C. Scordino, G. Lipari, A Resource Reservation Algorithm for Power-Aware Scheduling of Periodic and Aperiodic Real-Time Tasks, IEEE Transactions on Computers, December 2006. Juri Lelli (8): sched/cpufreq_schedutil: make use of DEADLINE utilization signal sched/deadline: move cpu frequency selection triggering points sched/cpufreq_schedutil: make worker kthread be SCHED_DEADLINE sched/cpufreq_schedutil: split utilization signals sched/cpufreq_schedutil: always consider all CPUs when deciding next freq sched/sched.h: remove sd arch_scale_freq_capacity parameter sched/sched.h: move arch_scale_{freq,cpu}_capacity outside CONFIG_SMP sched/deadline: make bandwidth enforcement scale-invariant include/linux/sched.h | 1 + include/linux/sched/cpufreq.h | 2 -- include/linux/sched/topology.h | 12 ++++---- include/uapi/linux/sched.h | 1 + kernel/sched/core.c | 19 ++++++++++-- kernel/sched/cpufreq_schedutil.c | 62 ++++++++++++++++++++++++---------------- kernel/sched/deadline.c | 39 ++++++++++++++++++++----- kernel/sched/fair.c | 4 +-- kernel/sched/sched.h | 27 +++++++++++++---- 9 files changed, 116 insertions(+), 51 deletions(-) -- 2.11.0