psi: Pressure states are unlikely

Move the unlikely branches out of line. This eliminates undesirable
jumps during wakeup and sleeps for workloads that aren't under any
sort of resource pressure.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20210303034659.91735-4-zhouchengming@bytedance.com

diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index 0fe6ff6..3907a6b 100644 (file)
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -219,17 +219,17 @@ static bool test_state(unsigned int *tasks, enum psi_states state)
 {
        switch (state) {
        case PSI_IO_SOME:
-               return tasks[NR_IOWAIT];
+               return unlikely(tasks[NR_IOWAIT]);
        case PSI_IO_FULL:
-               return tasks[NR_IOWAIT] && !tasks[NR_RUNNING];
+               return unlikely(tasks[NR_IOWAIT] && !tasks[NR_RUNNING]);
        case PSI_MEM_SOME:
-               return tasks[NR_MEMSTALL];
+               return unlikely(tasks[NR_MEMSTALL]);
        case PSI_MEM_FULL:
-               return tasks[NR_MEMSTALL] && !tasks[NR_RUNNING];
+               return unlikely(tasks[NR_MEMSTALL] && !tasks[NR_RUNNING]);
        case PSI_CPU_SOME:
-               return tasks[NR_RUNNING] > tasks[NR_ONCPU];
+               return unlikely(tasks[NR_RUNNING] > tasks[NR_ONCPU]);
        case PSI_CPU_FULL:
-               return tasks[NR_RUNNING] && !tasks[NR_ONCPU];
+               return unlikely(tasks[NR_RUNNING] && !tasks[NR_ONCPU]);
        case PSI_NONIDLE:
                return tasks[NR_IOWAIT] || tasks[NR_MEMSTALL] ||
                        tasks[NR_RUNNING];
@@ -729,7 +729,7 @@ static void psi_group_change(struct psi_group *group, int cpu,
         * task in a cgroup is in_memstall, the corresponding groupc
         * on that cpu is in PSI_MEM_FULL state.
         */
-       if (groupc->tasks[NR_ONCPU] && cpu_curr(cpu)->in_memstall)
+       if (unlikely(groupc->tasks[NR_ONCPU] && cpu_curr(cpu)->in_memstall))
                state_mask |= (1 << PSI_MEM_FULL);
 
        groupc->state_mask = state_mask;