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Date: Tue, 8 Jun 2021 15:04:52 -0400
From: Johannes Weiner <hannes@...xchg.org>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Suren Baghdasaryan <surenb@...gle.com>,
linux-kernel@...r.kernel.org, kernel-team@...com
Subject: [PATCH] psi: clean up time collection functions
The functions to read the per-cpu time buckets and aggregate them
don't have the greatest names and an awkward calling convention. Clean
this up to make things a bit more readable:
- Rename get_recent_times() to read_cpu_states() to make it clearer
this is about extracting psi state from one cpu, and not just the
times, either. Remove the pchanged_states return parameter and make
it the function's return value; rename the local variable 'states',
as it doesn't reflect changed states, but currently active ones.
- rename collect_percpu_times() to aggregate_cpus(), to indicate that
actual data processing happens there
- move calc_avgs() out of the way, closer to where it's being used.
Signed-off-by: Johannes Weiner <hannes@...xchg.org>
---
kernel/sched/psi.c | 90 ++++++++++++++++++++++------------------------
1 file changed, 42 insertions(+), 48 deletions(-)
diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index 9d647d974f55..1faf383f6ec4 100644
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -238,17 +238,15 @@ static bool test_state(unsigned int *tasks, enum psi_states state)
}
}
-static void get_recent_times(struct psi_group *group, int cpu,
- enum psi_aggregators aggregator, u32 *times,
- u32 *pchanged_states)
+static u32 snapshot_cpu_states(struct psi_group *group, int cpu,
+ enum psi_aggregators aggregator, u32 *times)
{
struct psi_group_cpu *groupc = per_cpu_ptr(group->pcpu, cpu);
u64 now, state_start;
enum psi_states s;
unsigned int seq;
u32 state_mask;
-
- *pchanged_states = 0;
+ u32 states = 0;
/* Snapshot a coherent view of the CPU state */
do {
@@ -279,37 +277,18 @@ static void get_recent_times(struct psi_group *group, int cpu,
times[s] = delta;
if (delta)
- *pchanged_states |= (1 << s);
+ states |= (1 << s);
}
-}
-static void calc_avgs(unsigned long avg[3], int missed_periods,
- u64 time, u64 period)
-{
- unsigned long pct;
-
- /* Fill in zeroes for periods of no activity */
- if (missed_periods) {
- avg[0] = calc_load_n(avg[0], EXP_10s, 0, missed_periods);
- avg[1] = calc_load_n(avg[1], EXP_60s, 0, missed_periods);
- avg[2] = calc_load_n(avg[2], EXP_300s, 0, missed_periods);
- }
-
- /* Sample the most recent active period */
- pct = div_u64(time * 100, period);
- pct *= FIXED_1;
- avg[0] = calc_load(avg[0], EXP_10s, pct);
- avg[1] = calc_load(avg[1], EXP_60s, pct);
- avg[2] = calc_load(avg[2], EXP_300s, pct);
+ return states;
}
-static void collect_percpu_times(struct psi_group *group,
- enum psi_aggregators aggregator,
- u32 *pchanged_states)
+static u32 aggregate_cpus(struct psi_group *group,
+ enum psi_aggregators aggregator)
{
u64 deltas[NR_PSI_STATES - 1] = { 0, };
unsigned long nonidle_total = 0;
- u32 changed_states = 0;
+ u32 states = 0;
int cpu;
int s;
@@ -324,11 +303,8 @@ static void 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, aggregator, times,
- &cpu_changed_states);
- changed_states |= cpu_changed_states;
+ states |= snapshot_cpu_states(group, cpu, aggregator, times);
nonidle = nsecs_to_jiffies(times[PSI_NONIDLE]);
nonidle_total += nonidle;
@@ -354,15 +330,34 @@ static void collect_percpu_times(struct psi_group *group,
group->total[aggregator][s] +=
div_u64(deltas[s], max(nonidle_total, 1UL));
- if (pchanged_states)
- *pchanged_states = changed_states;
+ return states;
+}
+
+static void calc_avgs(unsigned long avg[3], int missed_periods,
+ u64 time, u64 period)
+{
+ unsigned long pct;
+
+ /* Fill in zeroes for periods of no activity */
+ if (missed_periods) {
+ avg[0] = calc_load_n(avg[0], EXP_10s, 0, missed_periods);
+ avg[1] = calc_load_n(avg[1], EXP_60s, 0, missed_periods);
+ avg[2] = calc_load_n(avg[2], EXP_300s, 0, missed_periods);
+ }
+
+ /* Sample the most recent active period */
+ pct = div_u64(time * 100, period);
+ pct *= FIXED_1;
+ avg[0] = calc_load(avg[0], EXP_10s, pct);
+ avg[1] = calc_load(avg[1], EXP_60s, pct);
+ avg[2] = calc_load(avg[2], EXP_300s, pct);
}
static void update_averages(struct psi_group *group)
{
unsigned long missed_periods = 0;
u64 now, expires, period;
- u32 changed_states;
+ u32 states;
int s;
/* avgX= */
@@ -402,7 +397,7 @@ static void update_averages(struct psi_group *group)
group->avg_last_update = now;
group->avg_next_update = expires + ((1 + missed_periods) * psi_period);
- collect_percpu_times(group, PSI_AVGS, &changed_states);
+ states = aggregate_cpus(group, PSI_AVGS);
for (s = 0; s < NR_PSI_STATES - 1; s++) {
u32 sample;
@@ -430,7 +425,7 @@ static void update_averages(struct psi_group *group)
calc_avgs(group->avg[s], missed_periods, sample, period);
}
- if (changed_states & (1 << PSI_NONIDLE)) {
+ if (states & (1 << PSI_NONIDLE)) {
unsigned long delay;
delay = nsecs_to_jiffies(group->avg_next_update - now) + 1;
@@ -585,24 +580,24 @@ static void psi_schedule_poll_work(struct psi_group *group, unsigned long delay)
static void psi_poll_work(struct psi_group *group)
{
- u32 changed_states;
+ unsigned long delay;
+ u32 states;
u64 now;
mutex_lock(&group->trigger_lock);
now = sched_clock();
+ states = aggregate_cpus(group, PSI_POLL);
- collect_percpu_times(group, PSI_POLL, &changed_states);
-
- if (changed_states & group->poll_states) {
+ if (states & group->poll_states) {
/* Initialize trigger windows when entering polling mode */
if (now > group->polling_until)
init_triggers(group, now);
/*
- * Keep the monitor active for at least the duration of the
- * minimum tracking window as long as monitor states are
- * changing.
+ * Keep the monitor active for at least the duration
+ * of the minimum tracking window after a polled state
+ * has been observed.
*/
group->polling_until = now +
group->poll_min_period * UPDATES_PER_WINDOW;
@@ -616,9 +611,8 @@ static void psi_poll_work(struct psi_group *group)
if (now >= group->polling_next_update)
group->polling_next_update = update_triggers(group, now);
- psi_schedule_poll_work(group,
- nsecs_to_jiffies(group->polling_next_update - now) + 1);
-
+ delay = nsecs_to_jiffies(group->polling_next_update - now) + 1;
+ psi_schedule_poll_work(group, delay);
out:
mutex_unlock(&group->trigger_lock);
}
--
2.32.0
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