From: Kairui Song <kasong@xxxxxxxxxxx>
psi_group->parent has the same hierarchy as the cgroup it's in.
So just iterate through cgroup instead.
By adjusting the iteration logic, save some space in psi_group
struct, and the performance is actually better. I see a measurable
performance gain using mmtests/perfpipe:
(AVG of 100 test, ops/sec, the higher the better)
KVM guest on a i7-9700:
psi=0 root cgroup 5 levels of cgroup
Before: 59221 55352 47821
After: 60100 56036 50884
KVM guest on a Ryzen 9 5900HX:
psi=0 root cgroup 5 levels of cgroup
Before: 144566 138919 128888
After: 145812 139580 133514
Signed-off-by: Kairui Song <kasong@xxxxxxxxxxx>
Signed-off-by: Kairui Song <ryncsn@xxxxxxxxx>
---
include/linux/psi_types.h | 1 -
kernel/sched/psi.c | 47 ++++++++++++++++++++++++++++-----------
2 files changed, 34 insertions(+), 14 deletions(-)
diff --git a/include/linux/psi_types.h b/include/linux/psi_types.h
index 1e0a0d7ace3a..4066b846ce4a 100644
--- a/include/linux/psi_types.h
+++ b/include/linux/psi_types.h
@@ -154,7 +154,6 @@ struct psi_trigger {
};
struct psi_group {
- struct psi_group *parent;
bool enabled;
/* Protects data used by the aggregator */
diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index 8ac8b81bfee6..c74f8ce46f81 100644
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -858,15 +858,34 @@ static void psi_group_change(struct psi_group *group, int cpu,
schedule_delayed_work(&group->avgs_work, PSI_FREQ);
}
-static inline struct psi_group *task_psi_group(struct task_struct *task)
+static inline struct psi_group *psi_iter_first(struct task_struct *task, void **iter)
{
#ifdef CONFIG_CGROUPS
- if (static_branch_likely(&psi_cgroups_enabled))
- return cgroup_psi(task_dfl_cgroup(task));
+ if (static_branch_likely(&psi_cgroups_enabled)) {
+ struct cgroup *cgroup = task_dfl_cgroup(task);
+
+ *iter = cgroup_parent(cgroup);
+ return cgroup_psi(cgroup);
+ }
#endif
return &psi_system;
}
+static inline struct psi_group *psi_iter_next(void **iter)
+{
+#ifdef CONFIG_CGROUPS
+ if (static_branch_likely(&psi_cgroups_enabled)) {
+ struct cgroup *cgroup = *iter;
+
+ if (cgroup) {
+ *iter = cgroup_parent(cgroup);
+ return cgroup_psi(cgroup);
+ }
+ }
+#endif
+ return NULL;
+}
+
static void psi_flags_change(struct task_struct *task, int clear, int set)
{
if (((task->psi_flags & set) ||
@@ -886,6 +905,7 @@ void psi_task_change(struct task_struct *task, int clear, int set)
{
int cpu = task_cpu(task);
struct psi_group *group;
+ void *iter;
u64 now;
if (!task->pid)
@@ -895,16 +915,17 @@ void psi_task_change(struct task_struct *task, int clear, int set)
now = cpu_clock(cpu);
- group = task_psi_group(task);
+ group = psi_iter_first(task, &iter);
do {
psi_group_change(group, cpu, clear, set, now, true);
- } while ((group = group->parent));
+ } while ((group = psi_iter_next(&iter)));
}
void psi_task_switch(struct task_struct *prev, struct task_struct *next,
bool sleep)
{
struct psi_group *group, *common = NULL;
+ void *iter;
int cpu = task_cpu(prev);
u64 now = cpu_clock(cpu);
@@ -915,7 +936,7 @@ void psi_task_switch(struct task_struct *prev, struct task_struct *next,
* ancestors with @prev, those will already have @prev's
* TSK_ONCPU bit set, and we can stop the iteration there.
*/
- group = task_psi_group(next);
+ group = psi_iter_first(prev, &iter);
do {
if (per_cpu_ptr(group->pcpu, cpu)->state_mask &
PSI_ONCPU) {
@@ -924,7 +945,7 @@ void psi_task_switch(struct task_struct *prev, struct task_struct *next,
}
psi_group_change(group, cpu, 0, TSK_ONCPU, now, true);
- } while ((group = group->parent));
+ } while ((group = psi_iter_next(&iter)));
}
if (prev->pid) {
@@ -957,12 +978,12 @@ void psi_task_switch(struct task_struct *prev, struct task_struct *next,
psi_flags_change(prev, clear, set);
- group = task_psi_group(prev);
+ group = psi_iter_first(prev, &iter);
do {
if (group == common)
break;
psi_group_change(group, cpu, clear, set, now, wake_clock);
- } while ((group = group->parent));
+ } while ((group = psi_iter_next(&iter)));
/*
* TSK_ONCPU is handled up to the common ancestor. If there are
@@ -972,7 +993,7 @@ void psi_task_switch(struct task_struct *prev, struct task_struct *next,
*/
if ((prev->psi_flags ^ next->psi_flags) & ~TSK_ONCPU) {
clear &= ~TSK_ONCPU;
- for (; group; group = group->parent)
+ for (; group; group = psi_iter_next(&iter))
psi_group_change(group, cpu, clear, set, now, wake_clock);
}
}
@@ -983,6 +1004,7 @@ void psi_account_irqtime(struct task_struct *task, u32 delta)
{
int cpu = task_cpu(task);
struct psi_group *group;
+ void *iter;
struct psi_group_cpu *groupc;
u64 now;
@@ -991,7 +1013,7 @@ void psi_account_irqtime(struct task_struct *task, u32 delta)
now = cpu_clock(cpu);
- group = task_psi_group(task);
+ group = psi_iter_first(task, &iter);
do {
if (!group->enabled)
continue;
@@ -1007,7 +1029,7 @@ void psi_account_irqtime(struct task_struct *task, u32 delta)
if (group->poll_states & (1 << PSI_IRQ_FULL))
psi_schedule_poll_work(group, 1, false);
- } while ((group = group->parent));
+ } while ((group = psi_iter_next(&iter)));
}
#endif
@@ -1089,7 +1111,6 @@ int psi_cgroup_alloc(struct cgroup *cgroup)
return -ENOMEM;
}
group_init(cgroup->psi);
- cgroup->psi->parent = cgroup_psi(cgroup_parent(cgroup));
return 0;
}
--
2.39.1
