Vincent, What is the status of this after talks with the scheduler maintainers in Prague last week? Have you shared this with Peter Z et al.
Regards, Amit On Fri, Oct 21, 2011 at 12:52 PM, Vincent Guittot <vincent.guit...@linaro.org> wrote: > The sched_mc feature has been originally designed to improve power > consumption of multi-package system and several architecture functions > are available to tune the topology and the scheduler's parameters when > scheduler rebuilds the sched_domain hierarchy (change the > sched_mc_power_savings level). This patches series is a trial to > improve the power consumption of dual and quad cortex-A9 when the > sched_mc_power_savings is set to 2. The following patch's policy is to > accept up to 4 threads (can be configured) in the run queue of a core > before starting to load balance if cpu runs at low frequencies but to > accept only 1 thread for high frequencies, which is the normal > behaviour. The goal is to use only one cpu in light load situation and > both cpu in heavy load situation > > Patches [1-3] modify the ARM cpu topology according to > sched_mc_power_savings value and Cortex id > Patch [4] enables ARCH_POWER feature of the scheduler > Patch [5] adds ARCH_POWER function for ARM platform > Patches [6-7] modify the cpu_power of CA-9 according to > sched_mc_power_savings' level and current frequency. The main goal is > to increase the capacity of a core when using low cpu frequency in > order to pull tasks on this core. Note that this behaviour is not > really advised but it can be seen as an intermediate step between the > use of cpu hotplug (which is not a power saving feature) and a new > load balancer which will take into account low load situation on dual > core. > Patch [8] ensures that cpu0 is used in priority when only one CPU is running > Patch [9] adds some debugfs interface for test purpose > Patch [10] ensures that the cpu_power will be update periodically > Patch [11] fixes an issue around the trigger of ilb. > > TODO list: > -remove useless start of ilb when the core has capacity. > -add a method (DT, sysfs, ...) to set threshold for using 1 or 2 cpus > for dual CA-9 > -irq balancing > > The tests hereafter have been done on a u8500 with kernel linaro-3.1. > They check that there is no obvious lost of performance when > sched_mc=2. > > sysbench --test=cpu --num-threads=12 --max-time=20 run > Test execution summary: sched_mc=0 sched_mc=2 cpu hotplug > total number of events: 665 664 > 336 > per-request statistics: > min: 92.68ms 70.53ms > 618.89ms > avg: 361.75ms 361.38ms 725.29ms > max: 421.08ms 420.73ms 840.74ms > approx. 95 percentile: 402.28ms 390.53ms 760.17ms > > sysbench --test=threads --thread-locks=9 --num-threads=12 --max-time=20 run > Test execution summary: sched_mc=0 sched_mc=2 cpu hotplug > total number of events: 10000 10000 3129 > per-request statistics: > min: 1.62ms 1.70ms > 13.16ms > avg: 22.23ms 21.87ms > 76.77ms > max: 153.52ms 133.99ms 173.82ms > approx. 95 percentile: 54.12ms 52.65ms 136.32ms > > sysbench --test=threads --thread-locks=2 --num-threads=3 --max-time=20 run > Test execution summary: sched_mc=0 sched_mc=2 cpu hotplug > total number of events: 10000 10000 10000 > per-request statistics: > min: 1.38ms 1.38ms > 5.70ms > avg: 4.67ms 5.37ms > 11.85ms > max: 36.84ms 32.42ms 32.58ms > approx. 95 percentile: 14.34ms 12.89ms 21.30ms > > cyclictest -q -t -D 20 > Only one cpu is used during this test when sched_mc=2 whereas both cpu > are used when sched_mc=0 > Test execution summary: sched_mc=0 sched_mc=2 cpu hotplug > > Avg, Max: 15, 434 19, 2145 17, > 3556 > Avg, Max: 14, 104 19, 1686 17, > 3593 > > Regards, > Vincent > > _______________________________________________ > linaro-dev mailing list > linaro-dev@lists.linaro.org > http://lists.linaro.org/mailman/listinfo/linaro-dev > _______________________________________________ linaro-dev mailing list linaro-dev@lists.linaro.org http://lists.linaro.org/mailman/listinfo/linaro-dev
