[tip: sched/core] psi: Pressure states are unlikely

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The following commit has been merged into the sched/core branch of tip:

Commit-ID:     fddc8bab531e217806b84906681324377d741c6c
Gitweb:        https://git.kernel.org/tip/fddc8bab531e217806b84906681324377d741c6c
Author:        Johannes Weiner <hannes@xxxxxxxxxxx>
AuthorDate:    Wed, 03 Mar 2021 11:46:58 +08:00
Committer:     Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Sat, 06 Mar 2021 12:40:23 +01:00

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@xxxxxxxxxxx>
Signed-off-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Link: https://lkml.kernel.org/r/20210303034659.91735-4-zhouchengming@xxxxxxxxxxxxx
---
 kernel/sched/psi.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index 0fe6ff6..3907a6b 100644
--- 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;



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