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sched/cache: Assign preferred LLC ID to processes

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With cache-aware scheduling enabled, each task is assigned a
preferred LLC ID. This allows quick identification of the LLC domain
where the task prefers to run, similar to numa_preferred_nid in
NUMA balancing.

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/f2ceecba5858680349ad4ce9303a2121f0bb7272.1775065312.git.tim.c.chen@linux.intel.com
This commit is contained in:
Tim Chen
2026-04-01 14:52:18 -07:00
committed by Peter Zijlstra
parent b5ea300a17
commit 47d8696b95
3 changed files with 47 additions and 0 deletions
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1
include/linux/sched.h
View File

@@ -1409,6 +1409,7 @@ struct task_struct {
#ifdef CONFIG_SCHED_CACHE
struct callback_head cache_work;
int preferred_llc;
#endif
struct rseq_data rseq;

3
init/init_task.c
View File

@@ -215,6 +215,9 @@ struct task_struct init_task __aligned(L1_CACHE_BYTES) = {
.numa_group = NULL,
.numa_faults = NULL,
#endif
#ifdef CONFIG_SCHED_CACHE
.preferred_llc = -1,
#endif
#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
.kasan_depth = 1,
#endif

43
kernel/sched/fair.c
View File

@@ -1459,11 +1459,43 @@ static unsigned long fraction_mm_sched(struct rq *rq,
return div64_u64(NICE_0_LOAD * pcpu_sched->runtime, rq->cpu_runtime + 1);
}
static int get_pref_llc(struct task_struct *p, struct mm_struct *mm)
{
int mm_sched_llc = -1;
if (!mm)
return -1;
if (mm->sc_stat.cpu != -1) {
mm_sched_llc = llc_id(mm->sc_stat.cpu);
#ifdef CONFIG_NUMA_BALANCING
/*
* Don't assign preferred LLC if it
* conflicts with NUMA balancing.
* This can happen when sched_setnuma() gets
* called, however it is not much of an issue
* because we expect account_mm_sched() to get
* called fairly regularly -- at a higher rate
* than sched_setnuma() at least -- and thus the
* conflict only exists for a short period of time.
*/
if (static_branch_likely(&sched_numa_balancing) &&
p->numa_preferred_nid >= 0 &&
cpu_to_node(mm->sc_stat.cpu) != p->numa_preferred_nid)
mm_sched_llc = -1;
#endif
}
return mm_sched_llc;
}
static inline
void account_mm_sched(struct rq *rq, struct task_struct *p, s64 delta_exec)
{
struct sched_cache_time *pcpu_sched;
struct mm_struct *mm = p->mm;
int mm_sched_llc = -1;
unsigned long epoch;
if (!sched_cache_enabled())
@@ -1495,6 +1527,11 @@ void account_mm_sched(struct rq *rq, struct task_struct *p, s64 delta_exec)
if (mm->sc_stat.cpu != -1)
mm->sc_stat.cpu = -1;
}
mm_sched_llc = get_pref_llc(p, mm);
if (READ_ONCE(p->preferred_llc) != mm_sched_llc)
WRITE_ONCE(p->preferred_llc, mm_sched_llc);
}
static void task_tick_cache(struct rq *rq, struct task_struct *p)
@@ -1671,6 +1708,12 @@ void init_sched_mm(struct task_struct *p) { }
static void task_tick_cache(struct rq *rq, struct task_struct *p) { }
static inline int get_pref_llc(struct task_struct *p,
struct mm_struct *mm)
{
return -1;
}
#endif /* CONFIG_SCHED_CACHE */
/*