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sched/cache: Add migrate_llc_task migration type for cache-aware balancing

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Introduce a new migration type, migrate_llc_task, to support
cache-aware load balancing.

After identifying the busiest sched_group (having the most tasks
preferring the destination LLC), mark migrations with this type.
During load balancing, each runqueue in the busiest sched_group is
examined, and the runqueue with the highest number of tasks preferring
the destination CPU is selected as the busiest runqueue.

Co-developed-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/b9df27c19cc5121ddb2a7d1be7f9d52fec1563dc.1775065312.git.tim.c.chen@linux.intel.com
This commit is contained in:
Tim Chen 2026-04-01 14:52:25 -07:00 committed by Peter Zijlstra
parent f38cc2f0d8
commit e4c9a4cb24
1 changed files with 37 additions and 1 deletions
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38
kernel/sched/fair.c
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@ -9946,7 +9946,8 @@ enum migration_type {
migrate_load = 0, migrate_load = 0,
migrate_util, migrate_util,
migrate_task, migrate_task,
migrate_misfit migrate_misfit,
migrate_llc_task
}; };
#define LBF_ALL_PINNED 0x01 #define LBF_ALL_PINNED 0x01
@ -10560,6 +10561,10 @@ static int detach_tasks(struct lb_env *env)
env->imbalance = 0; env->imbalance = 0;
break; break;
case migrate_llc_task:
env->imbalance--;
break;
} }
detach_task(p, env); detach_task(p, env);
@ -12179,6 +12184,15 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s
return; return;
} }
#ifdef CONFIG_SCHED_CACHE
if (busiest->group_type == group_llc_balance) {
/* Move a task that prefer local LLC */
env->migration_type = migrate_llc_task;
env->imbalance = 1;
return;
}
#endif
if (busiest->group_type == group_imbalanced) { if (busiest->group_type == group_imbalanced) {
/* /*
* In the group_imb case we cannot rely on group-wide averages * In the group_imb case we cannot rely on group-wide averages
@ -12485,7 +12499,10 @@ static struct rq *sched_balance_find_src_rq(struct lb_env *env,
{ {
struct rq *busiest = NULL, *rq; struct rq *busiest = NULL, *rq;
unsigned long busiest_util = 0, busiest_load = 0, busiest_capacity = 1; unsigned long busiest_util = 0, busiest_load = 0, busiest_capacity = 1;
unsigned int __maybe_unused busiest_pref_llc = 0;
struct sched_domain __maybe_unused *sd_tmp;
unsigned int busiest_nr = 0; unsigned int busiest_nr = 0;
int __maybe_unused dst_llc;
int i; int i;
for_each_cpu_and(i, sched_group_span(group), env->cpus) { for_each_cpu_and(i, sched_group_span(group), env->cpus) {
@ -12613,6 +12630,23 @@ static struct rq *sched_balance_find_src_rq(struct lb_env *env,
break; break;
case migrate_llc_task:
#ifdef CONFIG_SCHED_CACHE
sd_tmp = rcu_dereference_all(rq->sd);
dst_llc = llc_id(env->dst_cpu);
if (sd_tmp && (unsigned)dst_llc < sd_tmp->llc_max) {
unsigned int this_pref_llc =
sd_tmp->llc_counts[dst_llc];
if (busiest_pref_llc < this_pref_llc) {
busiest_pref_llc = this_pref_llc;
busiest = rq;
}
}
#endif
break;
} }
} }
@ -12776,6 +12810,8 @@ static void update_lb_imbalance_stat(struct lb_env *env, struct sched_domain *sd
case migrate_misfit: case migrate_misfit:
__schedstat_add(sd->lb_imbalance_misfit[idle], env->imbalance); __schedstat_add(sd->lb_imbalance_misfit[idle], env->imbalance);
break; break;
case migrate_llc_task:
break;
} }
} }