We use iterate_groups() to iterate each level psi_group to update
PSI stats, which is a very hot path.
In current code, iterate_groups() have to use multiple branches and
cgroup_parent() to get parent psi_group for each level, which is not
very efficient.
This patch cache parent psi_group in struct psi_group, only need to get
psi_group of task itself first, then just use group->parent to iterate.
Signed-off-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
---
include/linux/psi_types.h | 2 ++
kernel/sched/psi.c | 49 +++++++++++++++------------------------
2 files changed, 21 insertions(+), 30 deletions(-)
diff --git a/include/linux/psi_types.h b/include/linux/psi_types.h
index 40c28171cd91..a0b746258c68 100644
--- a/include/linux/psi_types.h
+++ b/include/linux/psi_types.h
@@ -151,6 +151,8 @@ struct psi_trigger {
};
struct psi_group {
+ struct psi_group *parent;
+
/* Protects data used by the aggregator */
struct mutex avgs_lock;
diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index 2545a78f82d8..9a8aee80a087 100644
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -772,27 +772,12 @@ static void psi_group_change(struct psi_group *group, int cpu,
schedule_delayed_work(&group->avgs_work, PSI_FREQ);
}
-static struct psi_group *iterate_groups(struct task_struct *task, void **iter)
+static inline struct psi_group *task_psi_group(struct task_struct *task)
{
- if (*iter == &psi_system)
- return NULL;
-
#ifdef CONFIG_CGROUPS
- if (static_branch_likely(&psi_cgroups_enabled)) {
- struct cgroup *cgroup = NULL;
-
- if (!*iter)
- cgroup = task->cgroups->dfl_cgrp;
- else
- cgroup = cgroup_parent(*iter);
-
- if (cgroup && cgroup_parent(cgroup)) {
- *iter = cgroup;
- return cgroup_psi(cgroup);
- }
- }
+ if (static_branch_likely(&psi_cgroups_enabled))
+ return cgroup_psi(task_dfl_cgroup(task));
#endif
- *iter = &psi_system;
return &psi_system;
}
@@ -815,7 +800,6 @@ void psi_task_change(struct task_struct *task, int clear, int set)
{
int cpu = task_cpu(task);
struct psi_group *group;
- void *iter = NULL;
u64 now;
if (!task->pid)
@@ -825,8 +809,10 @@ void psi_task_change(struct task_struct *task, int clear, int set)
now = cpu_clock(cpu);
- while ((group = iterate_groups(task, &iter)))
+ group = task_psi_group(task);
+ do {
psi_group_change(group, cpu, clear, set, now, true);
+ } while ((group = group->parent));
}
void psi_task_switch(struct task_struct *prev, struct task_struct *next,
@@ -834,7 +820,6 @@ void psi_task_switch(struct task_struct *prev, struct task_struct *next,
{
struct psi_group *group, *common = NULL;
int cpu = task_cpu(prev);
- void *iter;
u64 now = cpu_clock(cpu);
if (next->pid) {
@@ -844,8 +829,8 @@ 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.
*/
- iter = NULL;
- while ((group = iterate_groups(next, &iter))) {
+ group = task_psi_group(next);
+ do {
if (per_cpu_ptr(group->pcpu, cpu)->state_mask &
PSI_ONCPU) {
common = group;
@@ -853,7 +838,7 @@ 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));
}
if (prev->pid) {
@@ -886,9 +871,12 @@ void psi_task_switch(struct task_struct *prev, struct task_struct *next,
psi_flags_change(prev, clear, set);
- iter = NULL;
- while ((group = iterate_groups(prev, &iter)) && group != common)
+ group = task_psi_group(prev);
+ do {
+ if (group == common)
+ break;
psi_group_change(group, cpu, clear, set, now, wake_clock);
+ } while ((group = group->parent));
/*
* TSK_ONCPU is handled up to the common ancestor. If there are
@@ -898,7 +886,7 @@ 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 = iterate_groups(prev, &iter))
+ for (; group; group = group->parent)
psi_group_change(group, cpu, clear, set, now, wake_clock);
}
}
@@ -908,7 +896,6 @@ void psi_task_switch(struct task_struct *prev, struct task_struct *next,
void psi_account_irqtime(struct task_struct *task, u32 delta)
{
int cpu = task_cpu(task);
- void *iter = NULL;
struct psi_group *group;
struct psi_group_cpu *groupc;
u64 now;
@@ -918,7 +905,8 @@ void psi_account_irqtime(struct task_struct *task, u32 delta)
now = cpu_clock(cpu);
- while ((group = iterate_groups(task, &iter))) {
+ group = task_psi_group(task);
+ do {
groupc = per_cpu_ptr(group->pcpu, cpu);
write_seqcount_begin(&groupc->seq);
@@ -930,7 +918,7 @@ void psi_account_irqtime(struct task_struct *task, u32 delta)
if (group->poll_states & (1 << PSI_IRQ_FULL))
psi_schedule_poll_work(group, 1);
- }
+ } while ((group = group->parent));
}
#endif
@@ -1010,6 +998,7 @@ int psi_cgroup_alloc(struct cgroup *cgroup)
return -ENOMEM;
}
group_init(cgroup->psi);
+ cgroup->psi->parent = cgroup_psi(cgroup_parent(cgroup));
return 0;
}
--
2.37.2
