From 2c6a8a48a701ca5d767f249eacb776f80858cbaa Mon Sep 17 00:00:00 2001 From: Morten Rasmussen Date: Tue, 6 Jan 2015 17:34:05 +0000 Subject: [PATCH] sched: Estimate energy impact of scheduling decisions Adds a generic energy-aware helper function, energy_diff(), that calculates energy impact of adding, removing, and migrating utilization in the system. cc: Ingo Molnar cc: Peter Zijlstra Signed-off-by: Morten Rasmussen --- kernel/sched/fair.c | 52 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 52 insertions(+) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index f3de37414a66..043715612227 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4893,6 +4893,58 @@ next_cpu: return 0; } +static inline bool cpu_in_sg(struct sched_group *sg, int cpu) +{ + return cpu != -1 && cpumask_test_cpu(cpu, sched_group_cpus(sg)); +} + +/* + * energy_diff(): Estimate the energy impact of changing the utilization + * distribution. eenv specifies the change: utilisation amount, source, and + * destination cpu. Source or destination cpu may be -1 in which case the + * utilization is removed from or added to the system (e.g. task wake-up). If + * both are specified, the utilization is migrated. + */ +static int energy_diff(struct energy_env *eenv) +{ + struct sched_domain *sd; + struct sched_group *sg; + int sd_cpu = -1, energy_before = 0, energy_after = 0; + + struct energy_env eenv_before = { + .util_delta = 0, + .src_cpu = eenv->src_cpu, + .dst_cpu = eenv->dst_cpu, + }; + + if (eenv->src_cpu == eenv->dst_cpu) + return 0; + + sd_cpu = (eenv->src_cpu != -1) ? eenv->src_cpu : eenv->dst_cpu; + sd = rcu_dereference(per_cpu(sd_ea, sd_cpu)); + + if (!sd) + return 0; /* Error */ + + sg = sd->groups; + + do { + if (cpu_in_sg(sg, eenv->src_cpu) || cpu_in_sg(sg, eenv->dst_cpu)) { + eenv_before.sg_top = eenv->sg_top = sg; + + if (sched_group_energy(&eenv_before)) + return 0; /* Invalid result abort */ + energy_before += eenv_before.energy; + + if (sched_group_energy(eenv)) + return 0; /* Invalid result abort */ + energy_after += eenv->energy; + } + } while (sg = sg->next, sg != sd->groups); + + return energy_after-energy_before; +} + /* * Detect M:N waker/wakee relationships via a switching-frequency heuristic. * A waker of many should wake a different task than the one last awakened -- 2.20.1