Messages in this thread | | | From | Pierre.Gondois@arm ... | Subject | [PATCH v2 0/2] sched/fair: find_energy_efficient_cpu() enhancements | Date | Thu, 29 Apr 2021 11:19:46 +0100 |
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From: Pierre Gondois <Pierre.Gondois@arm.com>
V2: - Split the patch in 2. [Quentin] - Add testing results to the cover-letter. [Dietmar] - Put back 'rcu_read_unlock()' to unlock the rcu earlier. [Dietmar] - Various comments. [Dietmar/Quentin]
This patchset prevents underflows in find_energy_efficient_cpu(). This is done in the second patch: sched/fair: Fix negative energy delta in find_energy_efficient_cpu()
The first patch: sched/fair: Only compute base_energy_pd if necessary prevents an unnecessary call to compute_energy() if no CPU is available in a performance domain (pd). When looping over the pds, it also allows to gather the calls to compute_energy(), reducing the chances of having utilization signals being concurrently updated and having a 'negative delta'.
The energy tests of the initial EAS enablement at: https://lkml.kernel.org/r/20181203095628.11858-1-quentin.perret@arm.com have been executed using LISA on a Juno-r2 (2xA57 + 4xA53).
To recall the test: "10 iterations of between 10 and 50 periodic rt-app tasks (16ms period, 5% duty-cycle) for 30 seconds with energy measurement. Unit is Joules. The goal is to save energy, so lower is better." "Energy is measured with the onboard energy meter. Numbers include consumption of big and little CPUs."
+----------+-----------------+-------------------------+ | | Without patches | With patches | +----------+--------+--------+------------------+------+ | Tasks nb | Mean | CI* | Mean | CI* | +----------+--------+--------+------------------+------+ | 10 | 6.57 | 0.24 | 6.46 (-1.63%) | 0.27 | | 20 | 12.44 | 0.21 | 12.44 (-0.01%) | 0.14 | | 30 | 19.10 | 0.78 | 18.75 (-1.85%) | 0.15 | | 40 | 27.27 | 0.53 | 27.35 (+0.31%) | 0.33 | | 50 | 36.55 | 0.42 | 36.28 (-0.74%) | 0.42 | +----------+-----------------+-------------------------+ CI: confidence interval
For each line, the intervals of values w/ w/o the patches are overlapping (consider Mean +/- CI). Thus, the energy results shouldn't have been impacted.
Pierre Gondois (2): sched/fair: Only compute base_energy_pd if necessary sched/fair: Fix negative energy delta in find_energy_efficient_cpu()
kernel/sched/fair.c | 66 ++++++++++++++++++++++++++------------------- 1 file changed, 38 insertions(+), 28 deletions(-)
-- 2.17.1
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