diff options
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/sched/ext_idle.c | 26 |
1 files changed, 22 insertions, 4 deletions
diff --git a/kernel/sched/ext_idle.c b/kernel/sched/ext_idle.c index c7e405262697..d9596427b5aa 100644 --- a/kernel/sched/ext_idle.c +++ b/kernel/sched/ext_idle.c @@ -424,18 +424,24 @@ static inline bool task_affinity_all(const struct task_struct *p) * - prefer the last used CPU to take advantage of cached data (L1, L2) and * branch prediction optimizations. * - * 3. Pick a CPU within the same LLC (Last-Level Cache): + * 3. Prefer @prev_cpu's SMT sibling: + * - if @prev_cpu is busy and no fully idle core is available, try to + * place the task on an idle SMT sibling of @prev_cpu; keeping the + * task on the same core makes migration cheaper, preserves L1 cache + * locality and reduces wakeup latency. + * + * 4. Pick a CPU within the same LLC (Last-Level Cache): * - if the above conditions aren't met, pick a CPU that shares the same * LLC, if the LLC domain is a subset of @cpus_allowed, to maintain * cache locality. * - * 4. Pick a CPU within the same NUMA node, if enabled: + * 5. Pick a CPU within the same NUMA node, if enabled: * - choose a CPU from the same NUMA node, if the node cpumask is a * subset of @cpus_allowed, to reduce memory access latency. * - * 5. Pick any idle CPU within the @cpus_allowed domain. + * 6. Pick any idle CPU within the @cpus_allowed domain. * - * Step 3 and 4 are performed only if the system has, respectively, + * Step 4 and 5 are performed only if the system has, respectively, * multiple LLCs / multiple NUMA nodes (see scx_selcpu_topo_llc and * scx_selcpu_topo_numa) and they don't contain the same subset of CPUs. * @@ -617,6 +623,18 @@ s32 scx_select_cpu_dfl(struct task_struct *p, s32 prev_cpu, u64 wake_flags, } /* + * Use @prev_cpu's sibling if it's idle. + */ + if (sched_smt_active()) { + for_each_cpu_and(cpu, cpu_smt_mask(prev_cpu), allowed) { + if (cpu == prev_cpu) + continue; + if (scx_idle_test_and_clear_cpu(cpu)) + goto out_unlock; + } + } + + /* * Search for any idle CPU in the same LLC domain. */ if (llc_cpus) { |