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sched/psi: Rearrange polling code in preparation

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[ Upstream commit 7fab21fa0d000a0ea32d73ce8eec68557c6c268b ]

Move a few functions up in the file to avoid forward declaration needed
in the patch implementing unprivileged PSI triggers.

Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Link: https://lore.kernel.org/r/20230330105418.77061-2-cerasuolodomenico@gmail.com
Stable-dep-of: aff037078eca ("sched/psi: use kernfs polling functions for PSI trigger polling")
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Domenico Cerasuolo 2023-03-30 12:54:15 +02:00 committed by Greg Kroah-Hartman
parent 7d8bba4da1
commit c176dda0a6
1 changed files with 108 additions and 108 deletions
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216
kernel/sched/psi.c
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@ -384,6 +384,114 @@ static void collect_percpu_times(struct psi_group *group,
*pchanged_states = changed_states;
}
/* Trigger tracking window manipulations */
static void window_reset(struct psi_window *win, u64 now, u64 value,
u64 prev_growth)
{
win->start_time = now;
win->start_value = value;
win->prev_growth = prev_growth;
}
/*
* PSI growth tracking window update and growth calculation routine.
*
* This approximates a sliding tracking window by interpolating
* partially elapsed windows using historical growth data from the
* previous intervals. This minimizes memory requirements (by not storing
* all the intermediate values in the previous window) and simplifies
* the calculations. It works well because PSI signal changes only in
* positive direction and over relatively small window sizes the growth
* is close to linear.
*/
static u64 window_update(struct psi_window *win, u64 now, u64 value)
{
u64 elapsed;
u64 growth;
elapsed = now - win->start_time;
growth = value - win->start_value;
/*
* After each tracking window passes win->start_value and
* win->start_time get reset and win->prev_growth stores
* the average per-window growth of the previous window.
* win->prev_growth is then used to interpolate additional
* growth from the previous window assuming it was linear.
*/
if (elapsed > win->size)
window_reset(win, now, value, growth);
else {
u32 remaining;
remaining = win->size - elapsed;
growth += div64_u64(win->prev_growth * remaining, win->size);
}
return growth;
}
static u64 update_triggers(struct psi_group *group, u64 now)
{
struct psi_trigger *t;
bool update_total = false;
u64 *total = group->total[PSI_POLL];
/*
* On subsequent updates, calculate growth deltas and let
* watchers know when their specified thresholds are exceeded.
*/
list_for_each_entry(t, &group->triggers, node) {
u64 growth;
bool new_stall;
new_stall = group->polling_total[t->state] != total[t->state];
/* Check for stall activity or a previous threshold breach */
if (!new_stall && !t->pending_event)
continue;
/*
* Check for new stall activity, as well as deferred
* events that occurred in the last window after the
* trigger had already fired (we want to ratelimit
* events without dropping any).
*/
if (new_stall) {
/*
* Multiple triggers might be looking at the same state,
* remember to update group->polling_total[] once we've
* been through all of them. Also remember to extend the
* polling time if we see new stall activity.
*/
update_total = true;
/* Calculate growth since last update */
growth = window_update(&t->win, now, total[t->state]);
if (!t->pending_event) {
if (growth < t->threshold)
continue;
t->pending_event = true;
}
}
/* Limit event signaling to once per window */
if (now < t->last_event_time + t->win.size)
continue;
/* Generate an event */
if (cmpxchg(&t->event, 0, 1) == 0)
wake_up_interruptible(&t->event_wait);
t->last_event_time = now;
/* Reset threshold breach flag once event got generated */
t->pending_event = false;
}
if (update_total)
memcpy(group->polling_total, total,
sizeof(group->polling_total));
return now + group->poll_min_period;
}
static u64 update_averages(struct psi_group *group, u64 now)
{
unsigned long missed_periods = 0;
@ -470,52 +578,6 @@ static void psi_avgs_work(struct work_struct *work)
mutex_unlock(&group->avgs_lock);
}
/* Trigger tracking window manipulations */
static void window_reset(struct psi_window *win, u64 now, u64 value,
u64 prev_growth)
{
win->start_time = now;
win->start_value = value;
win->prev_growth = prev_growth;
}
/*
* PSI growth tracking window update and growth calculation routine.
*
* This approximates a sliding tracking window by interpolating
* partially elapsed windows using historical growth data from the
* previous intervals. This minimizes memory requirements (by not storing
* all the intermediate values in the previous window) and simplifies
* the calculations. It works well because PSI signal changes only in
* positive direction and over relatively small window sizes the growth
* is close to linear.
*/
static u64 window_update(struct psi_window *win, u64 now, u64 value)
{
u64 elapsed;
u64 growth;
elapsed = now - win->start_time;
growth = value - win->start_value;
/*
* After each tracking window passes win->start_value and
* win->start_time get reset and win->prev_growth stores
* the average per-window growth of the previous window.
* win->prev_growth is then used to interpolate additional
* growth from the previous window assuming it was linear.
*/
if (elapsed > win->size)
window_reset(win, now, value, growth);
else {
u32 remaining;
remaining = win->size - elapsed;
growth += div64_u64(win->prev_growth * remaining, win->size);
}
return growth;
}
static void init_triggers(struct psi_group *group, u64 now)
{
struct psi_trigger *t;
@ -528,68 +590,6 @@ static void init_triggers(struct psi_group *group, u64 now)
group->polling_next_update = now + group->poll_min_period;
}
static u64 update_triggers(struct psi_group *group, u64 now)
{
struct psi_trigger *t;
bool update_total = false;
u64 *total = group->total[PSI_POLL];
/*
* On subsequent updates, calculate growth deltas and let
* watchers know when their specified thresholds are exceeded.
*/
list_for_each_entry(t, &group->triggers, node) {
u64 growth;
bool new_stall;
new_stall = group->polling_total[t->state] != total[t->state];
/* Check for stall activity or a previous threshold breach */
if (!new_stall && !t->pending_event)
continue;
/*
* Check for new stall activity, as well as deferred
* events that occurred in the last window after the
* trigger had already fired (we want to ratelimit
* events without dropping any).
*/
if (new_stall) {
/*
* Multiple triggers might be looking at the same state,
* remember to update group->polling_total[] once we've
* been through all of them. Also remember to extend the
* polling time if we see new stall activity.
*/
update_total = true;
/* Calculate growth since last update */
growth = window_update(&t->win, now, total[t->state]);
if (!t->pending_event) {
if (growth < t->threshold)
continue;
t->pending_event = true;
}
}
/* Limit event signaling to once per window */
if (now < t->last_event_time + t->win.size)
continue;
/* Generate an event */
if (cmpxchg(&t->event, 0, 1) == 0)
wake_up_interruptible(&t->event_wait);
t->last_event_time = now;
/* Reset threshold breach flag once event got generated */
t->pending_event = false;
}
if (update_total)
memcpy(group->polling_total, total,
sizeof(group->polling_total));
return now + group->poll_min_period;
}
/* Schedule polling if it's not already scheduled or forced. */
static void psi_schedule_poll_work(struct psi_group *group, unsigned long delay,
bool force)