From a8d0ca0b7f2f7b53565d1e30e509d3d74d1f5460 Mon Sep 17 00:00:00 2001 From: Tim Chen Date: Wed, 1 Apr 2026 14:52:20 -0700 Subject: sched/cache: Introduce per CPU's tasks LLC preference counter The lowest level of sched domain for each CPU is assigned an array where each element tracks the number of tasks preferring a given LLC, indexed from 0 to max_lid. Since each CPU has its dedicated sd, this implies that each CPU will have a dedicated task LLC preference counter. For example, sd->llc_counts[3] = 2 signifies that there are 2 tasks on this runqueue which prefer to run within LLC3. The load balancer can use this information to identify busy runqueues and migrate tasks to their preferred LLC domains. This array will be reallocated at runtime during sched domain rebuild. Introduce the buffer allocation mechanism, and the statistics will be calculated in the subsequent patch. Note: the LLC preference statistics of each CPU are reset on sched domain rebuild and may under count temporarily, until the CPU becomes idle and the count is cleared. This is a trade off to avoid complex data synchronization across sched domain builds. Suggested-by: Peter Zijlstra (Intel) Suggested-by: K Prateek Nayak Co-developed-by: Chen Yu Signed-off-by: Chen Yu Signed-off-by: Tim Chen Signed-off-by: Peter Zijlstra (Intel) Link: https://patch.msgid.link/42e79eceb8cd6be8a032401d481d101913bc5703.1775065312.git.tim.c.chen@linux.intel.com --- include/linux/sched/topology.h | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'include/linux') diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h index 159716fa0d3a..0036d6b4bd67 100644 --- a/include/linux/sched/topology.h +++ b/include/linux/sched/topology.h @@ -103,6 +103,11 @@ struct sched_domain { u64 max_newidle_lb_cost; unsigned long last_decay_max_lb_cost; +#ifdef CONFIG_SCHED_CACHE + unsigned int llc_max; + unsigned int *llc_counts __counted_by_ptr(llc_max); +#endif + #ifdef CONFIG_SCHEDSTATS /* sched_balance_rq() stats */ unsigned int lb_count[CPU_MAX_IDLE_TYPES]; -- cgit v1.2.3