diff options
Diffstat (limited to 'kernel/sched/psi.c')
| -rw-r--r-- | kernel/sched/psi.c | 1246 |
1 files changed, 787 insertions, 459 deletions
diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c index 8f45cdb6463b..bb56805e3d47 100644 --- a/kernel/sched/psi.c +++ b/kernel/sched/psi.c @@ -1,3 +1,4 @@ +// SPDX-License-Identifier: GPL-2.0 /* * Pressure stall information for CPU, memory and IO * @@ -34,12 +35,21 @@ * delayed on that resource such that nobody is advancing and the CPU * goes idle. This leaves both workload and CPU unproductive. * - * (Naturally, the FULL state doesn't exist for the CPU resource.) - * * SOME = nr_delayed_tasks != 0 - * FULL = nr_delayed_tasks != 0 && nr_running_tasks == 0 + * FULL = nr_delayed_tasks != 0 && nr_productive_tasks == 0 + * + * What it means for a task to be productive is defined differently + * for each resource. For IO, productive means a running task. For + * memory, productive means a running task that isn't a reclaimer. For + * CPU, productive means an on-CPU task. * - * The percentage of wallclock time spent in those compound stall + * Naturally, the FULL state doesn't exist for the CPU resource at the + * system level, but exist at the cgroup level. At the cgroup level, + * FULL means all non-idle tasks in the cgroup are delayed on the CPU + * resource which is being used by others outside of the cgroup or + * throttled by the cgroup cpu.max configuration. + * + * The percentage of wall clock time spent in those compound stall * states gives pressure numbers between 0 and 100 for each resource, * where the SOME percentage indicates workload slowdowns and the FULL * percentage indicates reduced CPU utilization: @@ -59,7 +69,7 @@ * states, we would have to conclude a CPU SOME pressure number of * 100%, since *somebody* is waiting on a runqueue at all * times. However, that is clearly not the amount of contention the - * workload is experiencing: only one out of 256 possible exceution + * workload is experiencing: only one out of 256 possible execution * threads will be contended at any given time, or about 0.4%. * * Conversely, consider a scenario of 4 tasks and 4 CPUs where at any @@ -73,18 +83,18 @@ * we have to base our calculation on the number of non-idle tasks in * conjunction with the number of available CPUs, which is the number * of potential execution threads. SOME becomes then the proportion of - * delayed tasks to possibe threads, and FULL is the share of possible + * delayed tasks to possible threads, and FULL is the share of possible * threads that are unproductive due to delays: * * threads = min(nr_nonidle_tasks, nr_cpus) * SOME = min(nr_delayed_tasks / threads, 1) - * FULL = (threads - min(nr_running_tasks, threads)) / threads + * FULL = (threads - min(nr_productive_tasks, threads)) / threads * * For the 257 number crunchers on 256 CPUs, this yields: * * threads = min(257, 256) * SOME = min(1 / 256, 1) = 0.4% - * FULL = (256 - min(257, 256)) / 256 = 0% + * FULL = (256 - min(256, 256)) / 256 = 0% * * For the 1 out of 4 memory-delayed tasks, this yields: * @@ -109,7 +119,7 @@ * For each runqueue, we track: * * tSOME[cpu] = time(nr_delayed_tasks[cpu] != 0) - * tFULL[cpu] = time(nr_delayed_tasks[cpu] && !nr_running_tasks[cpu]) + * tFULL[cpu] = time(nr_delayed_tasks[cpu] && !nr_productive_tasks[cpu]) * tNONIDLE[cpu] = time(nr_nonidle_tasks[cpu] != 0) * * and then periodically aggregate: @@ -127,24 +137,10 @@ * sampling of the aggregate task states would be. */ -#include "../workqueue_internal.h" -#include <linux/sched/loadavg.h> -#include <linux/seq_file.h> -#include <linux/proc_fs.h> -#include <linux/seqlock.h> -#include <linux/uaccess.h> -#include <linux/cgroup.h> -#include <linux/module.h> -#include <linux/sched.h> -#include <linux/ctype.h> -#include <linux/file.h> -#include <linux/poll.h> -#include <linux/psi.h> -#include "sched.h" - static int psi_bug __read_mostly; DEFINE_STATIC_KEY_FALSE(psi_disabled); +static DEFINE_STATIC_KEY_TRUE(psi_cgroups_enabled); #ifdef CONFIG_PSI_DEFAULT_DISABLED static bool psi_enable; @@ -164,7 +160,6 @@ __setup("psi=", setup_psi); #define EXP_300s 2034 /* 1/exp(2s/300s) */ /* PSI trigger definitions */ -#define WINDOW_MIN_US 500000 /* Min window size is 500ms */ #define WINDOW_MAX_US 10000000 /* Max window size is 10s */ #define UPDATES_PER_WINDOW 10 /* 10 updates per window */ @@ -179,59 +174,76 @@ struct psi_group psi_system = { static void psi_avgs_work(struct work_struct *work); +static void poll_timer_fn(struct timer_list *t); + static void group_init(struct psi_group *group) { int cpu; + group->enabled = true; for_each_possible_cpu(cpu) seqcount_init(&per_cpu_ptr(group->pcpu, cpu)->seq); group->avg_last_update = sched_clock(); group->avg_next_update = group->avg_last_update + psi_period; - INIT_DELAYED_WORK(&group->avgs_work, psi_avgs_work); mutex_init(&group->avgs_lock); - /* Init trigger-related members */ - atomic_set(&group->poll_scheduled, 0); - mutex_init(&group->trigger_lock); - INIT_LIST_HEAD(&group->triggers); - memset(group->nr_triggers, 0, sizeof(group->nr_triggers)); - group->poll_states = 0; - group->poll_min_period = U32_MAX; - memset(group->polling_total, 0, sizeof(group->polling_total)); - group->polling_next_update = ULLONG_MAX; - group->polling_until = 0; - rcu_assign_pointer(group->poll_kworker, NULL); + + /* Init avg trigger-related members */ + INIT_LIST_HEAD(&group->avg_triggers); + memset(group->avg_nr_triggers, 0, sizeof(group->avg_nr_triggers)); + INIT_DELAYED_WORK(&group->avgs_work, psi_avgs_work); + + /* Init rtpoll trigger-related members */ + atomic_set(&group->rtpoll_scheduled, 0); + mutex_init(&group->rtpoll_trigger_lock); + INIT_LIST_HEAD(&group->rtpoll_triggers); + group->rtpoll_min_period = U32_MAX; + group->rtpoll_next_update = ULLONG_MAX; + init_waitqueue_head(&group->rtpoll_wait); + timer_setup(&group->rtpoll_timer, poll_timer_fn, 0); + rcu_assign_pointer(group->rtpoll_task, NULL); } void __init psi_init(void) { if (!psi_enable) { static_branch_enable(&psi_disabled); + static_branch_disable(&psi_cgroups_enabled); return; } + if (!cgroup_psi_enabled()) + static_branch_disable(&psi_cgroups_enabled); + psi_period = jiffies_to_nsecs(PSI_FREQ); group_init(&psi_system); } -static bool test_state(unsigned int *tasks, enum psi_states state) +static u32 test_states(unsigned int *tasks, u32 state_mask) { - switch (state) { - case PSI_IO_SOME: - return tasks[NR_IOWAIT]; - case PSI_IO_FULL: - return tasks[NR_IOWAIT] && !tasks[NR_RUNNING]; - case PSI_MEM_SOME: - return tasks[NR_MEMSTALL]; - case PSI_MEM_FULL: - return tasks[NR_MEMSTALL] && !tasks[NR_RUNNING]; - case PSI_CPU_SOME: - return tasks[NR_RUNNING] > tasks[NR_ONCPU]; - case PSI_NONIDLE: - return tasks[NR_IOWAIT] || tasks[NR_MEMSTALL] || - tasks[NR_RUNNING]; - default: - return false; + const bool oncpu = state_mask & PSI_ONCPU; + + if (tasks[NR_IOWAIT]) { + state_mask |= BIT(PSI_IO_SOME); + if (!tasks[NR_RUNNING]) + state_mask |= BIT(PSI_IO_FULL); } + + if (tasks[NR_MEMSTALL]) { + state_mask |= BIT(PSI_MEM_SOME); + if (tasks[NR_RUNNING] == tasks[NR_MEMSTALL_RUNNING]) + state_mask |= BIT(PSI_MEM_FULL); + } + + if (tasks[NR_RUNNING] > oncpu) + state_mask |= BIT(PSI_CPU_SOME); + + if (tasks[NR_RUNNING] && !oncpu) + state_mask |= BIT(PSI_CPU_FULL); + + if (tasks[NR_IOWAIT] || tasks[NR_MEMSTALL] || tasks[NR_RUNNING]) + state_mask |= BIT(PSI_NONIDLE); + + return state_mask; } static void get_recent_times(struct psi_group *group, int cpu, @@ -239,6 +251,8 @@ static void get_recent_times(struct psi_group *group, int cpu, u32 *pchanged_states) { struct psi_group_cpu *groupc = per_cpu_ptr(group->pcpu, cpu); + int current_cpu = raw_smp_processor_id(); + unsigned int tasks[NR_PSI_TASK_COUNTS]; u64 now, state_start; enum psi_states s; unsigned int seq; @@ -253,6 +267,8 @@ static void get_recent_times(struct psi_group *group, int cpu, memcpy(times, groupc->times, sizeof(groupc->times)); state_mask = groupc->state_mask; state_start = groupc->state_start; + if (cpu == current_cpu) + memcpy(tasks, groupc->tasks, sizeof(groupc->tasks)); } while (read_seqcount_retry(&groupc->seq, seq)); /* Calculate state time deltas against the previous snapshot */ @@ -277,6 +293,28 @@ static void get_recent_times(struct psi_group *group, int cpu, if (delta) *pchanged_states |= (1 << s); } + + /* + * When collect_percpu_times() from the avgs_work, we don't want to + * re-arm avgs_work when all CPUs are IDLE. But the current CPU running + * this avgs_work is never IDLE, cause avgs_work can't be shut off. + * So for the current CPU, we need to re-arm avgs_work only when + * (NR_RUNNING > 1 || NR_IOWAIT > 0 || NR_MEMSTALL > 0), for other CPUs + * we can just check PSI_NONIDLE delta. + */ + if (current_work() == &group->avgs_work.work) { + bool reschedule; + + if (cpu == current_cpu) + reschedule = tasks[NR_RUNNING] + + tasks[NR_IOWAIT] + + tasks[NR_MEMSTALL] > 1; + else + reschedule = *pchanged_states & (1 << PSI_NONIDLE); + + if (reschedule) + *pchanged_states |= PSI_STATE_RESCHEDULE; + } } static void calc_avgs(unsigned long avg[3], int missed_periods, @@ -311,7 +349,7 @@ static void collect_percpu_times(struct psi_group *group, /* * Collect the per-cpu time buckets and average them into a - * single time sample that is normalized to wallclock time. + * single time sample that is normalized to wall clock time. * * For averaging, each CPU is weighted by its non-idle time in * the sampling period. This eliminates artifacts from uneven @@ -354,6 +392,114 @@ 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 void update_triggers(struct psi_group *group, u64 now, + enum psi_aggregators aggregator) +{ + struct psi_trigger *t; + u64 *total = group->total[aggregator]; + struct list_head *triggers; + u64 *aggregator_total; + + if (aggregator == PSI_AVGS) { + triggers = &group->avg_triggers; + aggregator_total = group->avg_total; + } else { + triggers = &group->rtpoll_triggers; + aggregator_total = group->rtpoll_total; + } + + /* + * On subsequent updates, calculate growth deltas and let + * watchers know when their specified thresholds are exceeded. + */ + list_for_each_entry(t, triggers, node) { + u64 growth; + bool new_stall; + + new_stall = aggregator_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) { + /* 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) { + if (t->of) + kernfs_notify(t->of->kn); + else + wake_up_interruptible(&t->event_wait); + } + t->last_event_time = now; + /* Reset threshold breach flag once event got generated */ + t->pending_event = false; + } +} + static u64 update_averages(struct psi_group *group, u64 now) { unsigned long missed_periods = 0; @@ -412,7 +558,6 @@ static void psi_avgs_work(struct work_struct *work) struct delayed_work *dwork; struct psi_group *group; u32 changed_states; - bool nonidle; u64 now; dwork = to_delayed_work(work); @@ -423,7 +568,6 @@ static void psi_avgs_work(struct work_struct *work) now = sched_clock(); collect_percpu_times(group, PSI_AVGS, &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 @@ -431,10 +575,12 @@ static void psi_avgs_work(struct work_struct *work) * Once restarted, we'll catch up the running averages in one * go - see calc_avgs() and missed_periods. */ - if (now >= group->avg_next_update) + if (now >= group->avg_next_update) { + update_triggers(group, now, PSI_AVGS); group->avg_next_update = update_averages(group, now); + } - if (nonidle) { + if (changed_states & PSI_STATE_RESCHEDULE) { schedule_delayed_work(dwork, nsecs_to_jiffies( group->avg_next_update - now) + 1); } @@ -442,194 +588,161 @@ static void psi_avgs_work(struct work_struct *work) mutex_unlock(&group->avgs_lock); } -/* Trigger tracking window manupulations */ -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) +static void init_rtpoll_triggers(struct psi_group *group, u64 now) { struct psi_trigger *t; - list_for_each_entry(t, &group->triggers, node) + list_for_each_entry(t, &group->rtpoll_triggers, node) window_reset(&t->win, now, group->total[PSI_POLL][t->state], 0); - memcpy(group->polling_total, group->total[PSI_POLL], - sizeof(group->polling_total)); - group->polling_next_update = now + group->poll_min_period; + memcpy(group->rtpoll_total, group->total[PSI_POLL], + sizeof(group->rtpoll_total)); + group->rtpoll_next_update = now + group->rtpoll_min_period; } -static u64 update_triggers(struct psi_group *group, u64 now) +/* Schedule rtpolling if it's not already scheduled or forced. */ +static void psi_schedule_rtpoll_work(struct psi_group *group, unsigned long delay, + bool force) { - struct psi_trigger *t; - bool new_stall = false; - u64 *total = group->total[PSI_POLL]; + struct task_struct *task; /* - * On subsequent updates, calculate growth deltas and let - * watchers know when their specified thresholds are exceeded. + * atomic_xchg should be called even when !force to provide a + * full memory barrier (see the comment inside psi_rtpoll_work). */ - list_for_each_entry(t, &group->triggers, node) { - u64 growth; - - /* Check for stall activity */ - if (group->polling_total[t->state] == total[t->state]) - continue; - - /* - * 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. - */ - new_stall = true; - - /* Calculate growth since last update */ - growth = window_update(&t->win, now, total[t->state]); - if (growth < t->threshold) - continue; - - /* 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; - } - - if (new_stall) - memcpy(group->polling_total, total, - sizeof(group->polling_total)); - - return now + group->poll_min_period; -} - -/* - * Schedule polling if it's not already scheduled. It's safe to call even from - * hotpath because even though kthread_queue_delayed_work takes worker->lock - * spinlock that spinlock is never contended due to poll_scheduled atomic - * preventing such competition. - */ -static void psi_schedule_poll_work(struct psi_group *group, unsigned long delay) -{ - struct kthread_worker *kworker; - - /* Do not reschedule if already scheduled */ - if (atomic_cmpxchg(&group->poll_scheduled, 0, 1) != 0) + if (atomic_xchg(&group->rtpoll_scheduled, 1) && !force) return; rcu_read_lock(); - kworker = rcu_dereference(group->poll_kworker); + task = rcu_dereference(group->rtpoll_task); /* * kworker might be NULL in case psi_trigger_destroy races with * psi_task_change (hotpath) which can't use locks */ - if (likely(kworker)) - kthread_queue_delayed_work(kworker, &group->poll_work, delay); + if (likely(task)) + mod_timer(&group->rtpoll_timer, jiffies + delay); else - atomic_set(&group->poll_scheduled, 0); + atomic_set(&group->rtpoll_scheduled, 0); rcu_read_unlock(); } -static void psi_poll_work(struct kthread_work *work) +static void psi_rtpoll_work(struct psi_group *group) { - struct kthread_delayed_work *dwork; - struct psi_group *group; + bool force_reschedule = false; u32 changed_states; u64 now; - dwork = container_of(work, struct kthread_delayed_work, work); - group = container_of(dwork, struct psi_group, poll_work); + mutex_lock(&group->rtpoll_trigger_lock); - atomic_set(&group->poll_scheduled, 0); + now = sched_clock(); - mutex_lock(&group->trigger_lock); + if (now > group->rtpoll_until) { + /* + * We are either about to start or might stop rtpolling if no + * state change was recorded. Resetting rtpoll_scheduled leaves + * a small window for psi_group_change to sneak in and schedule + * an immediate rtpoll_work before we get to rescheduling. One + * potential extra wakeup at the end of the rtpolling window + * should be negligible and rtpoll_next_update still keeps + * updates correctly on schedule. + */ + atomic_set(&group->rtpoll_scheduled, 0); + /* + * A task change can race with the rtpoll worker that is supposed to + * report on it. To avoid missing events, ensure ordering between + * rtpoll_scheduled and the task state accesses, such that if the + * rtpoll worker misses the state update, the task change is + * guaranteed to reschedule the rtpoll worker: + * + * rtpoll worker: + * atomic_set(rtpoll_scheduled, 0) + * smp_mb() + * LOAD states + * + * task change: + * STORE states + * if atomic_xchg(rtpoll_scheduled, 1) == 0: + * schedule rtpoll worker + * + * The atomic_xchg() implies a full barrier. + */ + smp_mb(); + } else { + /* The rtpolling window is not over, keep rescheduling */ + force_reschedule = true; + } - now = sched_clock(); collect_percpu_times(group, PSI_POLL, &changed_states); - if (changed_states & group->poll_states) { - /* Initialize trigger windows when entering polling mode */ - if (now > group->polling_until) - init_triggers(group, now); + if (changed_states & group->rtpoll_states) { + /* Initialize trigger windows when entering rtpolling mode */ + if (now > group->rtpoll_until) + init_rtpoll_triggers(group, now); /* * Keep the monitor active for at least the duration of the * minimum tracking window as long as monitor states are * changing. */ - group->polling_until = now + - group->poll_min_period * UPDATES_PER_WINDOW; + group->rtpoll_until = now + + group->rtpoll_min_period * UPDATES_PER_WINDOW; } - if (now > group->polling_until) { - group->polling_next_update = ULLONG_MAX; + if (now > group->rtpoll_until) { + group->rtpoll_next_update = ULLONG_MAX; goto out; } - if (now >= group->polling_next_update) - group->polling_next_update = update_triggers(group, now); + if (now >= group->rtpoll_next_update) { + if (changed_states & group->rtpoll_states) { + update_triggers(group, now, PSI_POLL); + memcpy(group->rtpoll_total, group->total[PSI_POLL], + sizeof(group->rtpoll_total)); + } + group->rtpoll_next_update = now + group->rtpoll_min_period; + } - psi_schedule_poll_work(group, - nsecs_to_jiffies(group->polling_next_update - now) + 1); + psi_schedule_rtpoll_work(group, + nsecs_to_jiffies(group->rtpoll_next_update - now) + 1, + force_reschedule); out: - mutex_unlock(&group->trigger_lock); + mutex_unlock(&group->rtpoll_trigger_lock); } -static void record_times(struct psi_group_cpu *groupc, int cpu, - bool memstall_tick) +static int psi_rtpoll_worker(void *data) +{ + struct psi_group *group = (struct psi_group *)data; + + sched_set_fifo_low(current); + + while (true) { + wait_event_interruptible(group->rtpoll_wait, + atomic_cmpxchg(&group->rtpoll_wakeup, 1, 0) || + kthread_should_stop()); + if (kthread_should_stop()) + break; + + psi_rtpoll_work(group); + } + return 0; +} + +static void poll_timer_fn(struct timer_list *t) +{ + struct psi_group *group = from_timer(group, t, rtpoll_timer); + + atomic_set(&group->rtpoll_wakeup, 1); + wake_up_interruptible(&group->rtpoll_wait); +} + +static void record_times(struct psi_group_cpu *groupc, u64 now) { u32 delta; - u64 now; - now = cpu_clock(cpu); delta = now - groupc->state_start; groupc->state_start = now; @@ -643,27 +756,13 @@ static void record_times(struct psi_group_cpu *groupc, int cpu, groupc->times[PSI_MEM_SOME] += delta; if (groupc->state_mask & (1 << PSI_MEM_FULL)) groupc->times[PSI_MEM_FULL] += delta; - else if (memstall_tick) { - u32 sample; - /* - * Since we care about lost potential, a - * memstall is FULL when there are no other - * working tasks, but also when the CPU is - * actively reclaiming and nothing productive - * could run even if it were runnable. - * - * When the timer tick sees a reclaiming CPU, - * regardless of runnable tasks, sample a FULL - * tick (or less if it hasn't been a full tick - * since the last state change). - */ - sample = min(delta, (u32)jiffies_to_nsecs(1)); - groupc->times[PSI_MEM_FULL] += sample; - } } - if (groupc->state_mask & (1 << PSI_CPU_SOME)) + if (groupc->state_mask & (1 << PSI_CPU_SOME)) { groupc->times[PSI_CPU_SOME] += delta; + if (groupc->state_mask & (1 << PSI_CPU_FULL)) + groupc->times[PSI_CPU_FULL] += delta; + } if (groupc->state_mask & (1 << PSI_NONIDLE)) groupc->times[PSI_NONIDLE] += delta; @@ -674,78 +773,112 @@ static void psi_group_change(struct psi_group *group, int cpu, bool wake_clock) { struct psi_group_cpu *groupc; - u32 state_mask = 0; unsigned int t, m; - enum psi_states s; + u32 state_mask; + u64 now; + lockdep_assert_rq_held(cpu_rq(cpu)); groupc = per_cpu_ptr(group->pcpu, cpu); /* - * First we assess the aggregate resource states this CPU's - * tasks have been in since the last change, and account any - * SOME and FULL time these may have resulted in. - * - * Then we update the task counts according to the state + * First we update the task counts according to the state * change requested through the @clear and @set bits. + * + * Then if the cgroup PSI stats accounting enabled, we + * assess the aggregate resource states this CPU's tasks + * have been in since the last change, and account any + * SOME and FULL time these may have resulted in. */ write_seqcount_begin(&groupc->seq); + now = cpu_clock(cpu); - record_times(groupc, cpu, false); + /* + * Start with TSK_ONCPU, which doesn't have a corresponding + * task count - it's just a boolean flag directly encoded in + * the state mask. Clear, set, or carry the current state if + * no changes are requested. + */ + if (unlikely(clear & TSK_ONCPU)) { + state_mask = 0; + clear &= ~TSK_ONCPU; + } else if (unlikely(set & TSK_ONCPU)) { + state_mask = PSI_ONCPU; + set &= ~TSK_ONCPU; + } else { + state_mask = groupc->state_mask & PSI_ONCPU; + } + /* + * The rest of the state mask is calculated based on the task + * counts. Update those first, then construct the mask. + */ for (t = 0, m = clear; m; m &= ~(1 << t), t++) { if (!(m & (1 << t))) continue; - if (groupc->tasks[t] == 0 && !psi_bug) { + if (groupc->tasks[t]) { + groupc->tasks[t]--; + } else if (!psi_bug) { printk_deferred(KERN_ERR "psi: task underflow! cpu=%d t=%d tasks=[%u %u %u %u] clear=%x set=%x\n", cpu, t, groupc->tasks[0], groupc->tasks[1], groupc->tasks[2], groupc->tasks[3], clear, set); psi_bug = 1; } - groupc->tasks[t]--; } for (t = 0; set; set &= ~(1 << t), t++) if (set & (1 << t)) groupc->tasks[t]++; - /* Calculate state mask representing active states */ - for (s = 0; s < NR_PSI_STATES; s++) { - if (test_state(groupc->tasks, s)) - state_mask |= (1 << s); + if (!group->enabled) { + /* + * On the first group change after disabling PSI, conclude + * the current state and flush its time. This is unlikely + * to matter to the user, but aggregation (get_recent_times) + * may have already incorporated the live state into times_prev; + * avoid a delta sample underflow when PSI is later re-enabled. + */ + if (unlikely(groupc->state_mask & (1 << PSI_NONIDLE))) + record_times(groupc, now); + + groupc->state_mask = state_mask; + + write_seqcount_end(&groupc->seq); + return; } + + state_mask = test_states(groupc->tasks, state_mask); + + /* + * Since we care about lost potential, a memstall is FULL + * when there are no other working tasks, but also when + * the CPU is actively reclaiming and nothing productive + * could run even if it were runnable. So when the current + * task in a cgroup is in_memstall, the corresponding groupc + * on that cpu is in PSI_MEM_FULL state. + */ + if (unlikely((state_mask & PSI_ONCPU) && cpu_curr(cpu)->in_memstall)) + state_mask |= (1 << PSI_MEM_FULL); + + record_times(groupc, now); + groupc->state_mask = state_mask; write_seqcount_end(&groupc->seq); - if (state_mask & group->poll_states) - psi_schedule_poll_work(group, 1); + if (state_mask & group->rtpoll_states) + psi_schedule_rtpoll_work(group, 1, false); if (wake_clock && !delayed_work_pending(&group->avgs_work)) 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) { #ifdef CONFIG_CGROUPS - struct cgroup *cgroup = NULL; - - if (!*iter) - cgroup = task->cgroups->dfl_cgrp; - else if (*iter == &psi_system) - return NULL; - else - cgroup = cgroup_parent(*iter); - - if (cgroup && cgroup_parent(cgroup)) { - *iter = cgroup; - return cgroup_psi(cgroup); - } -#else - if (*iter) - return NULL; + if (static_branch_likely(&psi_cgroups_enabled)) + return cgroup_psi(task_dfl_cgroup(task)); #endif - *iter = &psi_system; return &psi_system; } @@ -768,27 +901,16 @@ void psi_task_change(struct task_struct *task, int clear, int set) { int cpu = task_cpu(task); struct psi_group *group; - bool wake_clock = true; - void *iter = NULL; if (!task->pid) return; psi_flags_change(task, clear, set); - /* - * Periodic aggregation shuts off if there is a period of no - * task changes, so we wake it back up if necessary. However, - * don't do this if the task change is the aggregation worker - * itself going to sleep, or we'll ping-pong forever. - */ - if (unlikely((clear & TSK_RUNNING) && - (task->flags & PF_WQ_WORKER) && - wq_worker_last_func(task) == psi_avgs_work)) - wake_clock = false; - - while ((group = iterate_groups(task, &iter))) - psi_group_change(group, cpu, clear, set, wake_clock); + group = task_psi_group(task); + do { + psi_group_change(group, cpu, clear, set, true); + } while ((group = group->parent)); } void psi_task_switch(struct task_struct *prev, struct task_struct *next, @@ -796,59 +918,124 @@ 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; if (next->pid) { psi_flags_change(next, 0, TSK_ONCPU); /* - * When moving state between tasks, the group that - * contains them both does not change: we can stop - * updating the tree once we reach the first common - * ancestor. Iterate @next's ancestors until we - * encounter @prev's state. + * Set TSK_ONCPU on @next's cgroups. If @next shares any + * 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))) { - if (per_cpu_ptr(group->pcpu, cpu)->tasks[NR_ONCPU]) { + group = task_psi_group(next); + do { + if (per_cpu_ptr(group->pcpu, cpu)->state_mask & + PSI_ONCPU) { common = group; break; } psi_group_change(group, cpu, 0, TSK_ONCPU, true); - } + } while ((group = group->parent)); } - /* - * If this is a voluntary sleep, dequeue will have taken care - * of the outgoing TSK_ONCPU alongside TSK_RUNNING already. We - * only need to deal with it during preemption. - */ - if (sleep) - return; - if (prev->pid) { - psi_flags_change(prev, TSK_ONCPU, 0); + int clear = TSK_ONCPU, set = 0; + bool wake_clock = true; + + /* + * When we're going to sleep, psi_dequeue() lets us + * handle TSK_RUNNING, TSK_MEMSTALL_RUNNING and + * TSK_IOWAIT here, where we can combine it with + * TSK_ONCPU and save walking common ancestors twice. + */ + if (sleep) { + clear |= TSK_RUNNING; + if (prev->in_memstall) + clear |= TSK_MEMSTALL_RUNNING; + if (prev->in_iowait) + set |= TSK_IOWAIT; + + /* + * Periodic aggregation shuts off if there is a period of no + * task changes, so we wake it back up if necessary. However, + * don't do this if the task change is the aggregation worker + * itself going to sleep, or we'll ping-pong forever. + */ + if (unlikely((prev->flags & PF_WQ_WORKER) && + wq_worker_last_func(prev) == psi_avgs_work)) + wake_clock = false; + } - iter = NULL; - while ((group = iterate_groups(prev, &iter)) && group != common) - psi_group_change(group, cpu, TSK_ONCPU, 0, true); + psi_flags_change(prev, clear, set); + + group = task_psi_group(prev); + do { + if (group == common) + break; + psi_group_change(group, cpu, clear, set, wake_clock); + } while ((group = group->parent)); + + /* + * TSK_ONCPU is handled up to the common ancestor. If there are + * any other differences between the two tasks (e.g. prev goes + * to sleep, or only one task is memstall), finish propagating + * those differences all the way up to the root. + */ + if ((prev->psi_flags ^ next->psi_flags) & ~TSK_ONCPU) { + clear &= ~TSK_ONCPU; + for (; group; group = group->parent) + psi_group_change(group, cpu, clear, set, wake_clock); + } } } -void psi_memstall_tick(struct task_struct *task, int cpu) +#ifdef CONFIG_IRQ_TIME_ACCOUNTING +void psi_account_irqtime(struct rq *rq, struct task_struct *curr, struct task_struct *prev) { + int cpu = task_cpu(curr); struct psi_group *group; - void *iter = NULL; + struct psi_group_cpu *groupc; + s64 delta; + u64 irq; + + if (static_branch_likely(&psi_disabled) || !irqtime_enabled()) + return; - while ((group = iterate_groups(task, &iter))) { - struct psi_group_cpu *groupc; + if (!curr->pid) + return; + + lockdep_assert_rq_held(rq); + group = task_psi_group(curr); + if (prev && task_psi_group(prev) == group) + return; + + irq = irq_time_read(cpu); + delta = (s64)(irq - rq->psi_irq_time); + if (delta < 0) + return; + rq->psi_irq_time = irq; + + do { + u64 now; + + if (!group->enabled) + continue; groupc = per_cpu_ptr(group->pcpu, cpu); + write_seqcount_begin(&groupc->seq); - record_times(groupc, cpu, true); + now = cpu_clock(cpu); + + record_times(groupc, now); + groupc->times[PSI_IRQ_FULL] += delta; + write_seqcount_end(&groupc->seq); - } + + if (group->rtpoll_states & (1 << PSI_IRQ_FULL)) + psi_schedule_rtpoll_work(group, 1, false); + } while ((group = group->parent)); } +#endif /** * psi_memstall_enter - mark the beginning of a memory stall section @@ -876,10 +1063,11 @@ void psi_memstall_enter(unsigned long *flags) rq = this_rq_lock_irq(&rf); current->in_memstall = 1; - psi_task_change(current, 0, TSK_MEMSTALL); + psi_task_change(current, 0, TSK_MEMSTALL | TSK_MEMSTALL_RUNNING); rq_unlock_irq(rq, &rf); } +EXPORT_SYMBOL_GPL(psi_memstall_enter); /** * psi_memstall_leave - mark the end of an memory stall section @@ -905,33 +1093,42 @@ void psi_memstall_leave(unsigned long *flags) rq = this_rq_lock_irq(&rf); current->in_memstall = 0; - psi_task_change(current, TSK_MEMSTALL, 0); + psi_task_change(current, TSK_MEMSTALL | TSK_MEMSTALL_RUNNING, 0); rq_unlock_irq(rq, &rf); } +EXPORT_SYMBOL_GPL(psi_memstall_leave); #ifdef CONFIG_CGROUPS int psi_cgroup_alloc(struct cgroup *cgroup) { - if (static_branch_likely(&psi_disabled)) + if (!static_branch_likely(&psi_cgroups_enabled)) return 0; - cgroup->psi.pcpu = alloc_percpu(struct psi_group_cpu); - if (!cgroup->psi.pcpu) + cgroup->psi = kzalloc(sizeof(struct psi_group), GFP_KERNEL); + if (!cgroup->psi) + return -ENOMEM; + + cgroup->psi->pcpu = alloc_percpu(struct psi_group_cpu); + if (!cgroup->psi->pcpu) { + kfree(cgroup->psi); return -ENOMEM; - group_init(&cgroup->psi); + } + group_init(cgroup->psi); + cgroup->psi->parent = cgroup_psi(cgroup_parent(cgroup)); return 0; } void psi_cgroup_free(struct cgroup *cgroup) { - if (static_branch_likely(&psi_disabled)) + if (!static_branch_likely(&psi_cgroups_enabled)) return; - cancel_delayed_work_sync(&cgroup->psi.avgs_work); - free_percpu(cgroup->psi.pcpu); + cancel_delayed_work_sync(&cgroup->psi->avgs_work); + free_percpu(cgroup->psi->pcpu); /* All triggers must be removed by now */ - WARN_ONCE(cgroup->psi.poll_states, "psi: trigger leak\n"); + WARN_ONCE(cgroup->psi->rtpoll_states, "psi: trigger leak\n"); + kfree(cgroup->psi); } /** @@ -948,11 +1145,11 @@ void psi_cgroup_free(struct cgroup *cgroup) */ void cgroup_move_task(struct task_struct *task, struct css_set *to) { - unsigned int task_flags = 0; + unsigned int task_flags; struct rq_flags rf; struct rq *rq; - if (static_branch_likely(&psi_disabled)) { + if (!static_branch_likely(&psi_cgroups_enabled)) { /* * Lame to do this here, but the scheduler cannot be locked * from the outside, so we move cgroups from inside sched/. @@ -963,15 +1160,31 @@ void cgroup_move_task(struct task_struct *task, struct css_set *to) rq = task_rq_lock(task, &rf); - if (task_on_rq_queued(task)) { - task_flags = TSK_RUNNING; - if (task_current(rq, task)) - task_flags |= TSK_ONCPU; - } else if (task->in_iowait) - task_flags = TSK_IOWAIT; - - if (task->in_memstall) - task_flags |= TSK_MEMSTALL; + /* + * We may race with schedule() dropping the rq lock between + * deactivating prev and switching to next. Because the psi + * updates from the deactivation are deferred to the switch + * callback to save cgroup tree updates, the task's scheduling + * state here is not coherent with its psi state: + * + * schedule() cgroup_move_task() + * rq_lock() + * deactivate_task() + * p->on_rq = 0 + * psi_dequeue() // defers TSK_RUNNING & TSK_IOWAIT updates + * pick_next_task() + * rq_unlock() + * rq_lock() + * psi_task_change() // old cgroup + * task->cgroups = to + * psi_task_change() // new cgroup + * rq_unlock() + * rq_lock() + * psi_sched_switch() // does deferred updates in new cgroup + * + * Don't rely on the scheduling state. Use psi_flags instead. + */ + task_flags = task->psi_flags; if (task_flags) psi_task_change(task, task_flags, 0); @@ -984,16 +1197,54 @@ void cgroup_move_task(struct task_struct *task, struct css_set *to) task_rq_unlock(rq, task, &rf); } + +void psi_cgroup_restart(struct psi_group *group) +{ + int cpu; + + /* + * After we disable psi_group->enabled, we don't actually + * stop percpu tasks accounting in each psi_group_cpu, + * instead only stop test_states() loop, record_times() + * and averaging worker, see psi_group_change() for details. + * + * When disable cgroup PSI, this function has nothing to sync + * since cgroup pressure files are hidden and percpu psi_group_cpu + * would see !psi_group->enabled and only do task accounting. + * + * When re-enable cgroup PSI, this function use psi_group_change() + * to get correct state mask from test_states() loop on tasks[], + * and restart groupc->state_start from now, use .clear = .set = 0 + * here since no task status really changed. + */ + if (!group->enabled) + return; + + for_each_possible_cpu(cpu) { + struct rq *rq = cpu_rq(cpu); + struct rq_flags rf; + + rq_lock_irq(rq, &rf); + psi_group_change(group, cpu, 0, 0, true); + rq_unlock_irq(rq, &rf); + } +} #endif /* CONFIG_CGROUPS */ int psi_show(struct seq_file *m, struct psi_group *group, enum psi_res res) { + bool only_full = false; int full; u64 now; if (static_branch_likely(&psi_disabled)) return -EOPNOTSUPP; +#ifdef CONFIG_IRQ_TIME_ACCOUNTING + if (!irqtime_enabled() && res == PSI_IRQ) + return -EOPNOTSUPP; +#endif + /* Update averages before reporting them */ mutex_lock(&group->avgs_lock); now = sched_clock(); @@ -1002,18 +1253,25 @@ int psi_show(struct seq_file *m, struct psi_group *group, enum psi_res res) group->avg_next_update = update_averages(group, now); mutex_unlock(&group->avgs_lock); - for (full = 0; full < 2 - (res == PSI_CPU); full++) { - unsigned long avg[3]; - u64 total; +#ifdef CONFIG_IRQ_TIME_ACCOUNTING + only_full = res == PSI_IRQ; +#endif + + for (full = 0; full < 2 - only_full; full++) { + unsigned long avg[3] = { 0, }; + u64 total = 0; int w; - for (w = 0; w < 3; w++) - avg[w] = group->avg[res * 2 + full][w]; - total = div_u64(group->total[PSI_AVGS][res * 2 + full], - NSEC_PER_USEC); + /* CPU FULL is undefined at the system level */ + if (!(group == &psi_system && res == PSI_CPU && full)) { + for (w = 0; w < 3; w++) + avg[w] = group->avg[res * 2 + full][w]; + total = div_u64(group->total[PSI_AVGS][res * 2 + full], + NSEC_PER_USEC); + } seq_printf(m, "%s avg10=%lu.%02lu avg60=%lu.%02lu avg300=%lu.%02lu total=%llu\n", - full ? "full" : "some", + full || only_full ? "full" : "some", LOAD_INT(avg[0]), LOAD_FRAC(avg[0]), LOAD_INT(avg[1]), LOAD_FRAC(avg[1]), LOAD_INT(avg[2]), LOAD_FRAC(avg[2]), @@ -1023,47 +1281,25 @@ int psi_show(struct seq_file *m, struct psi_group *group, enum psi_res res) return 0; } -static int psi_io_show(struct seq_file *m, void *v) -{ - return psi_show(m, &psi_system, PSI_IO); -} - -static int psi_memory_show(struct seq_file *m, void *v) -{ - return psi_show(m, &psi_system, PSI_MEM); -} - -static int psi_cpu_show(struct seq_file *m, void *v) -{ - return psi_show(m, &psi_system, PSI_CPU); -} - -static int psi_io_open(struct inode *inode, struct file *file) -{ - return single_open(file, psi_io_show, NULL); -} - -static int psi_memory_open(struct inode *inode, struct file *file) -{ - return single_open(file, psi_memory_show, NULL); -} - -static int psi_cpu_open(struct inode *inode, struct file *file) -{ - return single_open(file, psi_cpu_show, NULL); -} - -struct psi_trigger *psi_trigger_create(struct psi_group *group, - char *buf, size_t nbytes, enum psi_res res) +struct psi_trigger *psi_trigger_create(struct psi_group *group, char *buf, + enum psi_res res, struct file *file, + struct kernfs_open_file *of) { struct psi_trigger *t; enum psi_states state; u32 threshold_us; + bool privileged; u32 window_us; if (static_branch_likely(&psi_disabled)) return ERR_PTR(-EOPNOTSUPP); + /* + * Checking the privilege here on file->f_cred implies that a privileged user + * could open the file and delegate the write to an unprivileged one. + */ + privileged = cap_raised(file->f_cred->cap_effective, CAP_SYS_RESOURCE); + if (sscanf(buf, "some %u %u", &threshold_us, &window_us) == 2) state = PSI_IO_SOME + res * 2; else if (sscanf(buf, "full %u %u", &threshold_us, &window_us) == 2) @@ -1071,11 +1307,22 @@ struct psi_trigger *psi_trigger_create(struct psi_group *group, else return ERR_PTR(-EINVAL); +#ifdef CONFIG_IRQ_TIME_ACCOUNTING + if (res == PSI_IRQ && --state != PSI_IRQ_FULL) + return ERR_PTR(-EINVAL); +#endif + if (state >= PSI_NONIDLE) return ERR_PTR(-EINVAL); - if (window_us < WINDOW_MIN_US || - window_us > WINDOW_MAX_US) + if (window_us == 0 || window_us > WINDOW_MAX_US) + return ERR_PTR(-EINVAL); + + /* + * Unprivileged users can only use 2s windows so that averages aggregation + * work is used, and no RT threads need to be spawned. + */ + if (!privileged && window_us % 2000000) return ERR_PTR(-EINVAL); /* Check threshold */ @@ -1090,123 +1337,137 @@ struct psi_trigger *psi_trigger_create(struct psi_group *group, t->state = state; t->threshold = threshold_us * NSEC_PER_USEC; t->win.size = window_us * NSEC_PER_USEC; - window_reset(&t->win, 0, 0, 0); + window_reset(&t->win, sched_clock(), + group->total[PSI_POLL][t->state], 0); t->event = 0; t->last_event_time = 0; - init_waitqueue_head(&t->event_wait); - kref_init(&t->refcount); - - mutex_lock(&group->trigger_lock); - - if (!rcu_access_pointer(group->poll_kworker)) { - struct sched_param param = { - .sched_priority = 1, - }; - struct kthread_worker *kworker; - - kworker = kthread_create_worker(0, "psimon"); - if (IS_ERR(kworker)) { - kfree(t); - mutex_unlock(&group->trigger_lock); - return ERR_CAST(kworker); + t->of = of; + if (!of) + init_waitqueue_head(&t->event_wait); + t->pending_event = false; + t->aggregator = privileged ? PSI_POLL : PSI_AVGS; + + if (privileged) { + mutex_lock(&group->rtpoll_trigger_lock); + + if (!rcu_access_pointer(group->rtpoll_task)) { + struct task_struct *task; + + task = kthread_create(psi_rtpoll_worker, group, "psimon"); + if (IS_ERR(task)) { + kfree(t); + mutex_unlock(&group->rtpoll_trigger_lock); + return ERR_CAST(task); + } + atomic_set(&group->rtpoll_wakeup, 0); + wake_up_process(task); + rcu_assign_pointer(group->rtpoll_task, task); } - sched_setscheduler_nocheck(kworker->task, SCHED_FIFO, ¶m); - kthread_init_delayed_work(&group->poll_work, - psi_poll_work); - rcu_assign_pointer(group->poll_kworker, kworker); - } - list_add(&t->node, &group->triggers); - group->poll_min_period = min(group->poll_min_period, - div_u64(t->win.size, UPDATES_PER_WINDOW)); - group->nr_triggers[t->state]++; - group->poll_states |= (1 << t->state); + list_add(&t->node, &group->rtpoll_triggers); + group->rtpoll_min_period = min(group->rtpoll_min_period, + div_u64(t->win.size, UPDATES_PER_WINDOW)); + group->rtpoll_nr_triggers[t->state]++; + group->rtpoll_states |= (1 << t->state); - mutex_unlock(&group->trigger_lock); + mutex_unlock(&group->rtpoll_trigger_lock); + } else { + mutex_lock(&group->avgs_lock); + list_add(&t->node, &group->avg_triggers); + group->avg_nr_triggers[t->state]++; + + mutex_unlock(&group->avgs_lock); + } return t; } -static void psi_trigger_destroy(struct kref *ref) +void psi_trigger_destroy(struct psi_trigger *t) { - struct psi_trigger *t = container_of(ref, struct psi_trigger, refcount); - struct psi_group *group = t->group; - struct kthread_worker *kworker_to_destroy = NULL; + struct psi_group *group; + struct task_struct *task_to_destroy = NULL; - if (static_branch_likely(&psi_disabled)) + /* + * We do not check psi_disabled since it might have been disabled after + * the trigger got created. + */ + if (!t) return; + group = t->group; /* - * Wakeup waiters to stop polling. Can happen if cgroup is deleted - * from under a polling process. + * Wakeup waiters to stop polling and clear the queue to prevent it from + * being accessed later. Can happen if cgroup is deleted from under a + * polling process. */ - wake_up_interruptible(&t->event_wait); - - mutex_lock(&group->trigger_lock); - - if (!list_empty(&t->node)) { - struct psi_trigger *tmp; - u64 period = ULLONG_MAX; - - list_del(&t->node); - group->nr_triggers[t->state]--; - if (!group->nr_triggers[t->state]) - group->poll_states &= ~(1 << t->state); - /* reset min update period for the remaining triggers */ - list_for_each_entry(tmp, &group->triggers, node) - period = min(period, div_u64(tmp->win.size, - UPDATES_PER_WINDOW)); - group->poll_min_period = period; - /* Destroy poll_kworker when the last trigger is destroyed */ - if (group->poll_states == 0) { - group->polling_until = 0; - kworker_to_destroy = rcu_dereference_protected( - group->poll_kworker, - lockdep_is_held(&group->trigger_lock)); - rcu_assign_pointer(group->poll_kworker, NULL); + if (t->of) + kernfs_notify(t->of->kn); + else + wake_up_interruptible(&t->event_wait); + + if (t->aggregator == PSI_AVGS) { + mutex_lock(&group->avgs_lock); + if (!list_empty(&t->node)) { + list_del(&t->node); + group->avg_nr_triggers[t->state]--; } + mutex_unlock(&group->avgs_lock); + } else { + mutex_lock(&group->rtpoll_trigger_lock); + if (!list_empty(&t->node)) { + struct psi_trigger *tmp; + u64 period = ULLONG_MAX; + + list_del(&t->node); + group->rtpoll_nr_triggers[t->state]--; + if (!group->rtpoll_nr_triggers[t->state]) + group->rtpoll_states &= ~(1 << t->state); + /* + * Reset min update period for the remaining triggers + * iff the destroying trigger had the min window size. + */ + if (group->rtpoll_min_period == div_u64(t->win.size, UPDATES_PER_WINDOW)) { + list_for_each_entry(tmp, &group->rtpoll_triggers, node) + period = min(period, div_u64(tmp->win.size, + UPDATES_PER_WINDOW)); + group->rtpoll_min_period = period; + } + /* Destroy rtpoll_task when the last trigger is destroyed */ + if (group->rtpoll_states == 0) { + group->rtpoll_until = 0; + task_to_destroy = rcu_dereference_protected( + group->rtpoll_task, + lockdep_is_held(&group->rtpoll_trigger_lock)); + rcu_assign_pointer(group->rtpoll_task, NULL); + del_timer(&group->rtpoll_timer); + } + } + mutex_unlock(&group->rtpoll_trigger_lock); } - mutex_unlock(&group->trigger_lock); - /* - * Wait for both *trigger_ptr from psi_trigger_replace and - * poll_kworker RCUs to complete their read-side critical sections - * before destroying the trigger and optionally the poll_kworker + * Wait for psi_schedule_rtpoll_work RCU to complete its read-side + * critical section before destroying the trigger and optionally the + * rtpoll_task. */ synchronize_rcu(); /* - * Destroy the kworker after releasing trigger_lock to prevent a - * deadlock while waiting for psi_poll_work to acquire trigger_lock + * Stop kthread 'psimon' after releasing rtpoll_trigger_lock to prevent + * a deadlock while waiting for psi_rtpoll_work to acquire + * rtpoll_trigger_lock */ - if (kworker_to_destroy) { + if (task_to_destroy) { /* * After the RCU grace period has expired, the worker - * can no longer be found through group->poll_kworker. - * But it might have been already scheduled before - * that - deschedule it cleanly before destroying it. + * can no longer be found through group->rtpoll_task. */ - kthread_cancel_delayed_work_sync(&group->poll_work); - atomic_set(&group->poll_scheduled, 0); - - kthread_destroy_worker(kworker_to_destroy); + kthread_stop(task_to_destroy); + atomic_set(&group->rtpoll_scheduled, 0); } kfree(t); } -void psi_trigger_replace(void **trigger_ptr, struct psi_trigger *new) -{ - struct psi_trigger *old = *trigger_ptr; - - if (static_branch_likely(&psi_disabled)) - return; - - rcu_assign_pointer(*trigger_ptr, new); - if (old) - kref_put(&old->refcount, psi_trigger_destroy); -} - __poll_t psi_trigger_poll(void **trigger_ptr, struct file *file, poll_table *wait) { @@ -1216,27 +1477,52 @@ __poll_t psi_trigger_poll(void **trigger_ptr, if (static_branch_likely(&psi_disabled)) return DEFAULT_POLLMASK | EPOLLERR | EPOLLPRI; - rcu_read_lock(); - - t = rcu_dereference(*(void __rcu __force **)trigger_ptr); - if (!t) { - rcu_read_unlock(); + t = smp_load_acquire(trigger_ptr); + if (!t) return DEFAULT_POLLMASK | EPOLLERR | EPOLLPRI; - } - kref_get(&t->refcount); - rcu_read_unlock(); - - poll_wait(file, &t->event_wait, wait); + if (t->of) + kernfs_generic_poll(t->of, wait); + else + poll_wait(file, &t->event_wait, wait); if (cmpxchg(&t->event, 1, 0) == 1) ret |= EPOLLPRI; - kref_put(&t->refcount, psi_trigger_destroy); - return ret; } +#ifdef CONFIG_PROC_FS +static int psi_io_show(struct seq_file *m, void *v) +{ + return psi_show(m, &psi_system, PSI_IO); +} + +static int psi_memory_show(struct seq_file *m, void *v) +{ + return psi_show(m, &psi_system, PSI_MEM); +} + +static int psi_cpu_show(struct seq_file *m, void *v) +{ + return psi_show(m, &psi_system, PSI_CPU); +} + +static int psi_io_open(struct inode *inode, struct file *file) +{ + return single_open(file, psi_io_show, NULL); +} + +static int psi_memory_open(struct inode *inode, struct file *file) +{ + return single_open(file, psi_memory_show, NULL); +} + +static int psi_cpu_open(struct inode *inode, struct file *file) +{ + return single_open(file, psi_cpu_show, NULL); +} + static ssize_t psi_write(struct file *file, const char __user *user_buf, size_t nbytes, enum psi_res res) { @@ -1257,14 +1543,24 @@ static ssize_t psi_write(struct file *file, const char __user *user_buf, buf[buf_size - 1] = '\0'; - new = psi_trigger_create(&psi_system, buf, nbytes, res); - if (IS_ERR(new)) - return PTR_ERR(new); - seq = file->private_data; + /* Take seq->lock to protect seq->private from concurrent writes */ mutex_lock(&seq->lock); - psi_trigger_replace(&seq->private, new); + + /* Allow only one trigger per file descriptor */ + if (seq->private) { + mutex_unlock(&seq->lock); + return -EBUSY; + } + + new = psi_trigger_create(&psi_system, buf, res, file, NULL); + if (IS_ERR(new)) { + mutex_unlock(&seq->lock); + return PTR_ERR(new); + } + + smp_store_release(&seq->private, new); mutex_unlock(&seq->lock); return nbytes; @@ -1299,7 +1595,7 @@ static int psi_fop_release(struct inode *inode, struct file *file) { struct seq_file *seq = file->private_data; - psi_trigger_replace(&seq->private, NULL); + psi_trigger_destroy(seq->private); return single_release(inode, file); } @@ -1330,14 +1626,46 @@ static const struct proc_ops psi_cpu_proc_ops = { .proc_release = psi_fop_release, }; +#ifdef CONFIG_IRQ_TIME_ACCOUNTING +static int psi_irq_show(struct seq_file *m, void *v) +{ + return psi_show(m, &psi_system, PSI_IRQ); +} + +static int psi_irq_open(struct inode *inode, struct file *file) +{ + return single_open(file, psi_irq_show, NULL); +} + +static ssize_t psi_irq_write(struct file *file, const char __user *user_buf, + size_t nbytes, loff_t *ppos) +{ + return psi_write(file, user_buf, nbytes, PSI_IRQ); +} + +static const struct proc_ops psi_irq_proc_ops = { + .proc_open = psi_irq_open, + .proc_read = seq_read, + .proc_lseek = seq_lseek, + .proc_write = psi_irq_write, + .proc_poll = psi_fop_poll, + .proc_release = psi_fop_release, +}; +#endif + static int __init psi_proc_init(void) { if (psi_enable) { proc_mkdir("pressure", NULL); - proc_create("pressure/io", 0, NULL, &psi_io_proc_ops); - proc_create("pressure/memory", 0, NULL, &psi_memory_proc_ops); - proc_create("pressure/cpu", 0, NULL, &psi_cpu_proc_ops); + proc_create("pressure/io", 0666, NULL, &psi_io_proc_ops); + proc_create("pressure/memory", 0666, NULL, &psi_memory_proc_ops); + proc_create("pressure/cpu", 0666, NULL, &psi_cpu_proc_ops); +#ifdef CONFIG_IRQ_TIME_ACCOUNTING + proc_create("pressure/irq", 0666, NULL, &psi_irq_proc_ops); +#endif } return 0; } module_init(psi_proc_init); + +#endif /* CONFIG_PROC_FS */ |