From: Andrea Righi <arighi@nvidia.com> mainline inclusion from mainline-v6.14-rc1 commit 02f034dcbf3dcb0989e638fdc00d10984dc2278b category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/IDC9YK Reference: https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commi... -------------------------------- Add a comments to clarify about the usage of cpumask_intersects(). Moreover, update scx_select_cpu_dfl() description clarifying that the final step of the idle selection logic involves searching for any idle CPU in the system that the task can use. Reviewed-by: Yury Norov <yury.norov@gmail.com> Signed-off-by: Andrea Righi <arighi@nvidia.com> Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Zicheng Qu <quzicheng@huawei.com> --- kernel/sched/ext.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c index d48a76c690e0..2a4b707407f8 100644 --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -3193,6 +3193,10 @@ static bool test_and_clear_cpu_idle(int cpu) * scx_pick_idle_cpu() can get caught in an infinite loop as * @cpu is never cleared from idle_masks.smt. Ensure that @cpu * is eventually cleared. + * + * NOTE: Use cpumask_intersects() and cpumask_test_cpu() to + * reduce memory writes, which may help alleviate cache + * coherence pressure. */ if (cpumask_intersects(smt, idle_masks.smt)) cpumask_andnot(idle_masks.smt, idle_masks.smt, smt); @@ -3421,6 +3425,8 @@ static void update_selcpu_topology(void) * 4. Pick a CPU within the same NUMA node, if enabled: * - choose a CPU from the same NUMA node to reduce memory access latency. * + * 5. Pick any idle CPU usable by the task. + * * Step 3 and 4 are performed only if the system has, respectively, multiple * LLC domains / multiple NUMA nodes (see scx_selcpu_topo_llc and * scx_selcpu_topo_numa). -- 2.34.1