sched: Create helper to calculate small_imbalance in fbg()
Impact: cleanup We have two places in find_busiest_group() where we need to calculate the minor imbalance before returning the busiest group. Encapsulate this functionality into a seperate helper function. Credit: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com> Signed-off-by: Gautham R Shenoy <ego@in.ibm.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Suresh Siddha <suresh.b.siddha@intel.com> Cc: "Balbir Singh" <balbir@in.ibm.com> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Cc: "Dhaval Giani" <dhaval@linux.vnet.ibm.com> Cc: Bharata B Rao <bharata@linux.vnet.ibm.com> LKML-Reference: <20090325091406.13992.54316.stgit@sofia.in.ibm.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
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131
kernel/sched.c
131
kernel/sched.c
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@ -3484,6 +3484,71 @@ group_next:
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} while (group != sd->groups);
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}
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/**
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* fix_small_imbalance - Calculate the minor imbalance that exists
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* amongst the groups of a sched_domain, during
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* load balancing.
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* @sds: Statistics of the sched_domain whose imbalance is to be calculated.
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* @this_cpu: The cpu at whose sched_domain we're performing load-balance.
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* @imbalance: Variable to store the imbalance.
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*/
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static inline void fix_small_imbalance(struct sd_lb_stats *sds,
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int this_cpu, unsigned long *imbalance)
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{
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unsigned long tmp, pwr_now = 0, pwr_move = 0;
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unsigned int imbn = 2;
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if (sds->this_nr_running) {
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sds->this_load_per_task /= sds->this_nr_running;
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if (sds->busiest_load_per_task >
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sds->this_load_per_task)
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imbn = 1;
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} else
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sds->this_load_per_task =
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cpu_avg_load_per_task(this_cpu);
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if (sds->max_load - sds->this_load + sds->busiest_load_per_task >=
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sds->busiest_load_per_task * imbn) {
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*imbalance = sds->busiest_load_per_task;
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return;
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}
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/*
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* OK, we don't have enough imbalance to justify moving tasks,
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* however we may be able to increase total CPU power used by
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* moving them.
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*/
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pwr_now += sds->busiest->__cpu_power *
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min(sds->busiest_load_per_task, sds->max_load);
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pwr_now += sds->this->__cpu_power *
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min(sds->this_load_per_task, sds->this_load);
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pwr_now /= SCHED_LOAD_SCALE;
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/* Amount of load we'd subtract */
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tmp = sg_div_cpu_power(sds->busiest,
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sds->busiest_load_per_task * SCHED_LOAD_SCALE);
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if (sds->max_load > tmp)
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pwr_move += sds->busiest->__cpu_power *
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min(sds->busiest_load_per_task, sds->max_load - tmp);
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/* Amount of load we'd add */
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if (sds->max_load * sds->busiest->__cpu_power <
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sds->busiest_load_per_task * SCHED_LOAD_SCALE)
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tmp = sg_div_cpu_power(sds->this,
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sds->max_load * sds->busiest->__cpu_power);
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else
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tmp = sg_div_cpu_power(sds->this,
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sds->busiest_load_per_task * SCHED_LOAD_SCALE);
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pwr_move += sds->this->__cpu_power *
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min(sds->this_load_per_task, sds->this_load + tmp);
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pwr_move /= SCHED_LOAD_SCALE;
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/* Move if we gain throughput */
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if (pwr_move > pwr_now)
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*imbalance = sds->busiest_load_per_task;
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}
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/******* find_busiest_group() helpers end here *********************/
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/*
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@ -3547,7 +3612,8 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
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*/
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if (sds.max_load < sds.avg_load) {
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*imbalance = 0;
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goto small_imbalance;
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fix_small_imbalance(&sds, this_cpu, imbalance);
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goto ret_busiest;
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}
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/* Don't want to pull so many tasks that a group would go idle */
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@ -3565,67 +3631,10 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
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* a think about bumping its value to force at least one task to be
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* moved
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*/
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if (*imbalance < sds.busiest_load_per_task) {
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unsigned long tmp, pwr_now, pwr_move;
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unsigned int imbn;
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small_imbalance:
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pwr_move = pwr_now = 0;
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imbn = 2;
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if (sds.this_nr_running) {
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sds.this_load_per_task /= sds.this_nr_running;
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if (sds.busiest_load_per_task >
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sds.this_load_per_task)
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imbn = 1;
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} else
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sds.this_load_per_task =
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cpu_avg_load_per_task(this_cpu);
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if (sds.max_load - sds.this_load +
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sds.busiest_load_per_task >=
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sds.busiest_load_per_task * imbn) {
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*imbalance = sds.busiest_load_per_task;
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return sds.busiest;
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}
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/*
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* OK, we don't have enough imbalance to justify moving tasks,
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* however we may be able to increase total CPU power used by
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* moving them.
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*/
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pwr_now += sds.busiest->__cpu_power *
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min(sds.busiest_load_per_task, sds.max_load);
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pwr_now += sds.this->__cpu_power *
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min(sds.this_load_per_task, sds.this_load);
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pwr_now /= SCHED_LOAD_SCALE;
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/* Amount of load we'd subtract */
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tmp = sg_div_cpu_power(sds.busiest,
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sds.busiest_load_per_task * SCHED_LOAD_SCALE);
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if (sds.max_load > tmp)
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pwr_move += sds.busiest->__cpu_power *
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min(sds.busiest_load_per_task,
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sds.max_load - tmp);
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/* Amount of load we'd add */
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if (sds.max_load * sds.busiest->__cpu_power <
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sds.busiest_load_per_task * SCHED_LOAD_SCALE)
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tmp = sg_div_cpu_power(sds.this,
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sds.max_load * sds.busiest->__cpu_power);
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else
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tmp = sg_div_cpu_power(sds.this,
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sds.busiest_load_per_task * SCHED_LOAD_SCALE);
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pwr_move += sds.this->__cpu_power *
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min(sds.this_load_per_task,
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sds.this_load + tmp);
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pwr_move /= SCHED_LOAD_SCALE;
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/* Move if we gain throughput */
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if (pwr_move > pwr_now)
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*imbalance = sds.busiest_load_per_task;
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}
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if (*imbalance < sds.busiest_load_per_task)
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fix_small_imbalance(&sds, this_cpu, imbalance);
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ret_busiest:
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return sds.busiest;
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out_balanced:
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