From df0d98475954d655571979aa061ecb07d7e00392 Mon Sep 17 00:00:00 2001 From: "Peter Zijlstra (Intel)" Date: Wed, 1 Apr 2026 14:52:13 -0700 Subject: sched/cache: Introduce infrastructure for cache-aware load balancing Adds infrastructure to enable cache-aware load balancing, which improves cache locality by grouping tasks that share resources within the same cache domain. This reduces cache misses and improves overall data access efficiency. In this initial implementation, threads belonging to the same process are treated as entities that likely share working sets. The mechanism tracks per-process CPU occupancy across cache domains and attempts to migrate threads toward cache-hot domains where their process already has active threads, thereby enhancing locality. This provides a basic model for cache affinity. While the current code targets the last-level cache (LLC), the approach could be extended to other domain types such as clusters (L2) or node-internal groupings. At present, the mechanism selects the CPU within an LLC that has the highest recent runtime. Subsequent patches in this series will use this information in the load-balancing path to guide task placement toward preferred LLCs. In the future, more advanced policies could be integrated through NUMA balancing-for example, migrating a task to its preferred LLC when spare capacity exists, or swapping tasks across LLCs to improve cache affinity. Grouping of tasks could also be generalized from that of a process to be that of a NUMA group, or be user configurable. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Chen Yu Signed-off-by: Tim Chen Signed-off-by: Peter Zijlstra (Intel) Link: https://patch.msgid.link/6269a53221b9439b9ca00d18a9d1946fb64d8cff.1775065312.git.tim.c.chen@linux.intel.com --- kernel/fork.c | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'kernel/fork.c') diff --git a/kernel/fork.c b/kernel/fork.c index 079802cb6100..61042bc3482d 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -724,6 +724,7 @@ void __mmdrop(struct mm_struct *mm) cleanup_lazy_tlbs(mm); WARN_ON_ONCE(mm == current->active_mm); + mm_destroy_sched(mm); mm_free_pgd(mm); mm_free_id(mm); destroy_context(mm); @@ -1125,6 +1126,9 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p, if (mm_alloc_cid(mm, p)) goto fail_cid; + if (mm_alloc_sched(mm)) + goto fail_sched; + if (percpu_counter_init_many(mm->rss_stat, 0, GFP_KERNEL_ACCOUNT, NR_MM_COUNTERS)) goto fail_pcpu; @@ -1134,6 +1138,8 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p, return mm; fail_pcpu: + mm_destroy_sched(mm); +fail_sched: mm_destroy_cid(mm); fail_cid: destroy_context(mm); -- cgit v1.2.3 From 1628b25248d0742b2ce9c7cfa59cd183e35f37e1 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Tue, 12 May 2026 02:56:17 +0000 Subject: sched: Add blocked_donor link to task for smarter mutex handoffs Add link to the task this task is proxying for, and use it so the mutex owner can do an intelligent hand-off of the mutex to the task that the owner is running on behalf. [jstultz: This patch was split out from larger proxy patch] Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Juri Lelli Signed-off-by: Valentin Schneider Signed-off-by: Connor O'Brien Signed-off-by: John Stultz Signed-off-by: Peter Zijlstra (Intel) Link: https://patch.msgid.link/20260512025635.2840817-8-jstultz@google.com --- kernel/fork.c | 1 + 1 file changed, 1 insertion(+) (limited to 'kernel/fork.c') diff --git a/kernel/fork.c b/kernel/fork.c index a679b2448234..6fcca1db0af3 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -2224,6 +2224,7 @@ __latent_entropy struct task_struct *copy_process( lockdep_init_task(p); p->blocked_on = NULL; /* not blocked yet */ + p->blocked_donor = NULL; /* nobody is boosting p yet */ #ifdef CONFIG_BCACHE p->sequential_io = 0; -- cgit v1.2.3