[PATCH v6 5/7] psi: track changed states

From: Suren Baghdasaryan
Date: Tue Mar 19 2019 - 19:57:04 EST


Introduce changed_states parameter into collect_percpu_times to track
the states changed since the last update.

Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
---
kernel/sched/psi.c | 24 ++++++++++++++++++------
1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index ace5ed97b186..1b99eeffaa25 100644
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -210,7 +210,8 @@ static bool test_state(unsigned int *tasks, enum psi_states state)
}
}

-static void get_recent_times(struct psi_group *group, int cpu, u32 *times)
+static void get_recent_times(struct psi_group *group, int cpu, u32 *times,
+ u32 *pchanged_states)
{
struct psi_group_cpu *groupc = per_cpu_ptr(group->pcpu, cpu);
u64 now, state_start;
@@ -218,6 +219,8 @@ static void get_recent_times(struct psi_group *group, int cpu, u32 *times)
unsigned int seq;
u32 state_mask;

+ *pchanged_states = 0;
+
/* Snapshot a coherent view of the CPU state */
do {
seq = read_seqcount_begin(&groupc->seq);
@@ -246,6 +249,8 @@ static void get_recent_times(struct psi_group *group, int cpu, u32 *times)
groupc->times_prev[s] = times[s];

times[s] = delta;
+ if (delta)
+ *pchanged_states |= (1 << s);
}
}

@@ -269,10 +274,11 @@ static void calc_avgs(unsigned long avg[3], int missed_periods,
avg[2] = calc_load(avg[2], EXP_300s, pct);
}

-static bool collect_percpu_times(struct psi_group *group)
+static void collect_percpu_times(struct psi_group *group, u32 *pchanged_states)
{
u64 deltas[NR_PSI_STATES - 1] = { 0, };
unsigned long nonidle_total = 0;
+ u32 changed_states = 0;
int cpu;
int s;

@@ -287,8 +293,11 @@ static bool collect_percpu_times(struct psi_group *group)
for_each_possible_cpu(cpu) {
u32 times[NR_PSI_STATES];
u32 nonidle;
+ u32 cpu_changed_states;

- get_recent_times(group, cpu, times);
+ get_recent_times(group, cpu, times,
+ &cpu_changed_states);
+ changed_states |= cpu_changed_states;

nonidle = nsecs_to_jiffies(times[PSI_NONIDLE]);
nonidle_total += nonidle;
@@ -313,7 +322,8 @@ static bool collect_percpu_times(struct psi_group *group)
for (s = 0; s < NR_PSI_STATES - 1; s++)
group->total[s] += div_u64(deltas[s], max(nonidle_total, 1UL));

- return nonidle_total;
+ if (pchanged_states)
+ *pchanged_states = changed_states;
}

static u64 update_averages(struct psi_group *group, u64 now)
@@ -373,6 +383,7 @@ static void psi_avgs_work(struct work_struct *work)
{
struct delayed_work *dwork;
struct psi_group *group;
+ u32 changed_states;
bool nonidle;
u64 now;

@@ -383,7 +394,8 @@ static void psi_avgs_work(struct work_struct *work)

now = sched_clock();

- nonidle = collect_percpu_times(group);
+ collect_percpu_times(group, &changed_states);
+ nonidle = changed_states & (1 << PSI_NONIDLE);
/*
* If there is task activity, periodically fold the per-cpu
* times and feed samples into the running averages. If things
@@ -719,7 +731,7 @@ int psi_show(struct seq_file *m, struct psi_group *group, enum psi_res res)
/* Update averages before reporting them */
mutex_lock(&group->avgs_lock);
now = sched_clock();
- collect_percpu_times(group);
+ collect_percpu_times(group, NULL);
if (now >= group->avg_next_update)
group->avg_next_update = update_averages(group, now);
mutex_unlock(&group->avgs_lock);
--
2.21.0.225.g810b269d1ac-goog