diff options
| -rw-r--r-- | Documentation/accounting/psi.txt | 107 | ||||
| -rw-r--r-- | include/linux/psi.h | 8 | ||||
| -rw-r--r-- | include/linux/psi_types.h | 82 | ||||
| -rw-r--r-- | kernel/cgroup/cgroup.c | 71 | ||||
| -rw-r--r-- | kernel/sched/psi.c | 494 |
5 files changed, 742 insertions, 20 deletions
diff --git a/Documentation/accounting/psi.txt b/Documentation/accounting/psi.txt index 7e71c9c1d8e9..5cbe5659e3b7 100644 --- a/Documentation/accounting/psi.txt +++ b/Documentation/accounting/psi.txt @@ -63,6 +63,110 @@ as well as medium and long term trends. The total absolute stall time spikes which wouldn't necessarily make a dent in the time averages, or to average trends over custom time frames. +Monitoring for pressure thresholds +================================== + +Users can register triggers and use poll() to be woken up when resource +pressure exceeds certain thresholds. + +A trigger describes the maximum cumulative stall time over a specific +time window, e.g. 100ms of total stall time within any 500ms window to +generate a wakeup event. + +To register a trigger user has to open psi interface file under +/proc/pressure/ representing the resource to be monitored and write the +desired threshold and time window. The open file descriptor should be +used to wait for trigger events using select(), poll() or epoll(). +The following format is used: + +<some|full> <stall amount in us> <time window in us> + +For example writing "some 150000 1000000" into /proc/pressure/memory +would add 150ms threshold for partial memory stall measured within +1sec time window. Writing "full 50000 1000000" into /proc/pressure/io +would add 50ms threshold for full io stall measured within 1sec time window. + +Triggers can be set on more than one psi metric and more than one trigger +for the same psi metric can be specified. However for each trigger a separate +file descriptor is required to be able to poll it separately from others, +therefore for each trigger a separate open() syscall should be made even +when opening the same psi interface file. + +Monitors activate only when system enters stall state for the monitored +psi metric and deactivates upon exit from the stall state. While system is +in the stall state psi signal growth is monitored at a rate of 10 times per +tracking window. + +The kernel accepts window sizes ranging from 500ms to 10s, therefore min +monitoring update interval is 50ms and max is 1s. Min limit is set to +prevent overly frequent polling. Max limit is chosen as a high enough number +after which monitors are most likely not needed and psi averages can be used +instead. + +When activated, psi monitor stays active for at least the duration of one +tracking window to avoid repeated activations/deactivations when system is +bouncing in and out of the stall state. + +Notifications to the userspace are rate-limited to one per tracking window. + +The trigger will de-register when the file descriptor used to define the +trigger is closed. + +Userspace monitor usage example +=============================== + +#include <errno.h> +#include <fcntl.h> +#include <stdio.h> +#include <poll.h> +#include <string.h> +#include <unistd.h> + +/* + * Monitor memory partial stall with 1s tracking window size + * and 150ms threshold. + */ +int main() { + const char trig[] = "some 150000 1000000"; + struct pollfd fds; + int n; + + fds.fd = open("/proc/pressure/memory", O_RDWR | O_NONBLOCK); + if (fds.fd < 0) { + printf("/proc/pressure/memory open error: %s\n", + strerror(errno)); + return 1; + } + fds.events = POLLPRI; + + if (write(fds.fd, trig, strlen(trig) + 1) < 0) { + printf("/proc/pressure/memory write error: %s\n", + strerror(errno)); + return 1; + } + + printf("waiting for events...\n"); + while (1) { + n = poll(&fds, 1, -1); + if (n < 0) { + printf("poll error: %s\n", strerror(errno)); + return 1; + } + if (fds.revents & POLLERR) { + printf("got POLLERR, event source is gone\n"); + return 0; + } + if (fds.revents & POLLPRI) { + printf("event triggered!\n"); + } else { + printf("unknown event received: 0x%x\n", fds.revents); + return 1; + } + } + + return 0; +} + Cgroup2 interface ================= @@ -71,3 +175,6 @@ mounted, pressure stall information is also tracked for tasks grouped into cgroups. Each subdirectory in the cgroupfs mountpoint contains cpu.pressure, memory.pressure, and io.pressure files; the format is the same as the /proc/pressure/ files. + +Per-cgroup psi monitors can be specified and used the same way as +system-wide ones. diff --git a/include/linux/psi.h b/include/linux/psi.h index 7006008d5b72..af892c290116 100644 --- a/include/linux/psi.h +++ b/include/linux/psi.h @@ -4,6 +4,7 @@ #include <linux/jump_label.h> #include <linux/psi_types.h> #include <linux/sched.h> +#include <linux/poll.h> struct seq_file; struct css_set; @@ -26,6 +27,13 @@ int psi_show(struct seq_file *s, struct psi_group *group, enum psi_res res); int psi_cgroup_alloc(struct cgroup *cgrp); void psi_cgroup_free(struct cgroup *cgrp); void cgroup_move_task(struct task_struct *p, struct css_set *to); + +struct psi_trigger *psi_trigger_create(struct psi_group *group, + char *buf, size_t nbytes, enum psi_res res); +void psi_trigger_replace(void **trigger_ptr, struct psi_trigger *t); + +__poll_t psi_trigger_poll(void **trigger_ptr, struct file *file, + poll_table *wait); #endif #else /* CONFIG_PSI */ diff --git a/include/linux/psi_types.h b/include/linux/psi_types.h index 4d1c1f67be18..07aaf9b82241 100644 --- a/include/linux/psi_types.h +++ b/include/linux/psi_types.h @@ -1,8 +1,11 @@ #ifndef _LINUX_PSI_TYPES_H #define _LINUX_PSI_TYPES_H +#include <linux/kthread.h> #include <linux/seqlock.h> #include <linux/types.h> +#include <linux/kref.h> +#include <linux/wait.h> #ifdef CONFIG_PSI @@ -44,6 +47,12 @@ enum psi_states { NR_PSI_STATES = 6, }; +enum psi_aggregators { + PSI_AVGS = 0, + PSI_POLL, + NR_PSI_AGGREGATORS, +}; + struct psi_group_cpu { /* 1st cacheline updated by the scheduler */ @@ -65,7 +74,55 @@ struct psi_group_cpu { /* 2nd cacheline updated by the aggregator */ /* Delta detection against the sampling buckets */ - u32 times_prev[NR_PSI_STATES] ____cacheline_aligned_in_smp; + u32 times_prev[NR_PSI_AGGREGATORS][NR_PSI_STATES] + ____cacheline_aligned_in_smp; +}; + +/* PSI growth tracking window */ +struct psi_window { + /* Window size in ns */ + u64 size; + + /* Start time of the current window in ns */ + u64 start_time; + + /* Value at the start of the window */ + u64 start_value; + + /* Value growth in the previous window */ + u64 prev_growth; +}; + +struct psi_trigger { + /* PSI state being monitored by the trigger */ + enum psi_states state; + + /* User-spacified threshold in ns */ + u64 threshold; + + /* List node inside triggers list */ + struct list_head node; + + /* Backpointer needed during trigger destruction */ + struct psi_group *group; + + /* Wait queue for polling */ + wait_queue_head_t event_wait; + + /* Pending event flag */ + int event; + + /* Tracking window */ + struct psi_window win; + + /* + * Time last event was generated. Used for rate-limiting + * events to one per window + */ + u64 last_event_time; + + /* Refcounting to prevent premature destruction */ + struct kref refcount; }; struct psi_group { @@ -79,11 +136,32 @@ struct psi_group { u64 avg_total[NR_PSI_STATES - 1]; u64 avg_last_update; u64 avg_next_update; + + /* Aggregator work control */ struct delayed_work avgs_work; /* Total stall times and sampled pressure averages */ - u64 total[NR_PSI_STATES - 1]; + u64 total[NR_PSI_AGGREGATORS][NR_PSI_STATES - 1]; unsigned long avg[NR_PSI_STATES - 1][3]; + + /* Monitor work control */ + atomic_t poll_scheduled; + struct kthread_worker __rcu *poll_kworker; + struct kthread_delayed_work poll_work; + + /* Protects data used by the monitor */ + struct mutex trigger_lock; + + /* Configured polling triggers */ + struct list_head triggers; + u32 nr_triggers[NR_PSI_STATES - 1]; + u32 poll_states; + u64 poll_min_period; + + /* Total stall times at the start of monitor activation */ + u64 polling_total[NR_PSI_STATES - 1]; + u64 polling_next_update; + u64 polling_until; }; #else /* CONFIG_PSI */ diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 327f37c9fdfa..1140357d46f4 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -3550,7 +3550,65 @@ static int cgroup_cpu_pressure_show(struct seq_file *seq, void *v) { return psi_show(seq, &seq_css(seq)->cgroup->psi, PSI_CPU); } -#endif + +static ssize_t cgroup_pressure_write(struct kernfs_open_file *of, char *buf, + size_t nbytes, enum psi_res res) +{ + struct psi_trigger *new; + struct cgroup *cgrp; + + cgrp = cgroup_kn_lock_live(of->kn, false); + if (!cgrp) + return -ENODEV; + + cgroup_get(cgrp); + cgroup_kn_unlock(of->kn); + + new = psi_trigger_create(&cgrp->psi, buf, nbytes, res); + if (IS_ERR(new)) { + cgroup_put(cgrp); + return PTR_ERR(new); + } + + psi_trigger_replace(&of->priv, new); + + cgroup_put(cgrp); + + return nbytes; +} + +static ssize_t cgroup_io_pressure_write(struct kernfs_open_file *of, + char *buf, size_t nbytes, + loff_t off) +{ + return cgroup_pressure_write(of, buf, nbytes, PSI_IO); +} + +static ssize_t cgroup_memory_pressure_write(struct kernfs_open_file *of, + char *buf, size_t nbytes, + loff_t off) +{ + return cgroup_pressure_write(of, buf, nbytes, PSI_MEM); +} + +static ssize_t cgroup_cpu_pressure_write(struct kernfs_open_file *of, + char *buf, size_t nbytes, + loff_t off) +{ + return cgroup_pressure_write(of, buf, nbytes, PSI_CPU); +} + +static __poll_t cgroup_pressure_poll(struct kernfs_open_file *of, + poll_table *pt) +{ + return psi_trigger_poll(&of->priv, of->file, pt); +} + +static void cgroup_pressure_release(struct kernfs_open_file *of) +{ + psi_trigger_replace(&of->priv, NULL); +} +#endif /* CONFIG_PSI */ static int cgroup_freeze_show(struct seq_file *seq, void *v) { @@ -4745,18 +4803,27 @@ static struct cftype cgroup_base_files[] = { .name = "io.pressure", .flags = CFTYPE_NOT_ON_ROOT, .seq_show = cgroup_io_pressure_show, + .write = cgroup_io_pressure_write, + .poll = cgroup_pressure_poll, + .release = cgroup_pressure_release, }, { .name = "memory.pressure", .flags = CFTYPE_NOT_ON_ROOT, .seq_show = cgroup_memory_pressure_show, + .write = cgroup_memory_pressure_write, + .poll = cgroup_pressure_poll, + .release = cgroup_pressure_release, }, { .name = "cpu.pressure", .flags = CFTYPE_NOT_ON_ROOT, .seq_show = cgroup_cpu_pressure_show, + .write = cgroup_cpu_pressure_write, + .poll = cgroup_pressure_poll, + .release = cgroup_pressure_release, }, -#endif +#endif /* CONFIG_PSI */ { } /* terminate */ }; diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c index 1b99eeffaa25..e88918e0bb6d 100644 --- a/kernel/sched/psi.c +++ b/kernel/sched/psi.c @@ -4,6 +4,9 @@ * Copyright (c) 2018 Facebook, Inc. * Author: Johannes Weiner <hannes@cmpxchg.org> * + * Polling support by Suren Baghdasaryan <surenb@google.com> + * Copyright (c) 2018 Google, Inc. + * * When CPU, memory and IO are contended, tasks experience delays that * reduce throughput and introduce latencies into the workload. Memory * and IO contention, in addition, can cause a full loss of forward @@ -129,9 +132,13 @@ #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" @@ -156,6 +163,11 @@ __setup("psi=", setup_psi); #define EXP_60s 1981 /* 1/exp(2s/60s) */ #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 */ + /* Sampling frequency in nanoseconds */ static u64 psi_period __read_mostly; @@ -176,6 +188,17 @@ static void group_init(struct psi_group *group) group->avg_next_update = sched_clock() + 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); } void __init psi_init(void) @@ -210,7 +233,8 @@ 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, + enum psi_aggregators aggregator, u32 *times, u32 *pchanged_states) { struct psi_group_cpu *groupc = per_cpu_ptr(group->pcpu, cpu); @@ -245,8 +269,8 @@ static void get_recent_times(struct psi_group *group, int cpu, u32 *times, if (state_mask & (1 << s)) times[s] += now - state_start; - delta = times[s] - groupc->times_prev[s]; - groupc->times_prev[s] = times[s]; + delta = times[s] - groupc->times_prev[aggregator][s]; + groupc->times_prev[aggregator][s] = times[s]; times[s] = delta; if (delta) @@ -274,7 +298,9 @@ static void calc_avgs(unsigned long avg[3], int missed_periods, avg[2] = calc_load(avg[2], EXP_300s, pct); } -static void collect_percpu_times(struct psi_group *group, u32 *pchanged_states) +static void collect_percpu_times(struct psi_group *group, + enum psi_aggregators aggregator, + u32 *pchanged_states) { u64 deltas[NR_PSI_STATES - 1] = { 0, }; unsigned long nonidle_total = 0; @@ -295,7 +321,7 @@ static void collect_percpu_times(struct psi_group *group, u32 *pchanged_states) u32 nonidle; u32 cpu_changed_states; - get_recent_times(group, cpu, times, + get_recent_times(group, cpu, aggregator, times, &cpu_changed_states); changed_states |= cpu_changed_states; @@ -320,7 +346,8 @@ static void collect_percpu_times(struct psi_group *group, u32 *pchanged_states) /* total= */ for (s = 0; s < NR_PSI_STATES - 1; s++) - group->total[s] += div_u64(deltas[s], max(nonidle_total, 1UL)); + group->total[aggregator][s] += + div_u64(deltas[s], max(nonidle_total, 1UL)); if (pchanged_states) *pchanged_states = changed_states; @@ -352,7 +379,7 @@ static u64 update_averages(struct psi_group *group, u64 now) for (s = 0; s < NR_PSI_STATES - 1; s++) { u32 sample; - sample = group->total[s] - group->avg_total[s]; + sample = group->total[PSI_AVGS][s] - group->avg_total[s]; /* * Due to the lockless sampling of the time buckets, * recorded time deltas can slip into the next period, @@ -394,7 +421,7 @@ static void psi_avgs_work(struct work_struct *work) now = sched_clock(); - collect_percpu_times(group, &changed_states); + collect_percpu_times(group, PSI_AVGS, &changed_states); nonidle = changed_states & (1 << PSI_NONIDLE); /* * If there is task activity, periodically fold the per-cpu @@ -414,6 +441,187 @@ 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 += div_u64(win->prev_growth * remaining, win->size); + } + + return growth; +} + +static void init_triggers(struct psi_group *group, u64 now) +{ + struct psi_trigger *t; + + list_for_each_entry(t, &group->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; +} + +static u64 update_triggers(struct psi_group *group, u64 now) +{ + struct psi_trigger *t; + bool new_stall = 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; + + /* 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) + return; + + rcu_read_lock(); + + kworker = rcu_dereference(group->poll_kworker); + /* + * 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); + else + atomic_set(&group->poll_scheduled, 0); + + rcu_read_unlock(); +} + +static void psi_poll_work(struct kthread_work *work) +{ + struct kthread_delayed_work *dwork; + struct psi_group *group; + u32 changed_states; + u64 now; + + dwork = container_of(work, struct kthread_delayed_work, work); + group = container_of(dwork, struct psi_group, poll_work); + + atomic_set(&group->poll_scheduled, 0); + + mutex_lock(&group->trigger_lock); + + 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); + + /* + * 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; + } + + if (now > group->polling_until) { + group->polling_next_update = ULLONG_MAX; + goto out; + } + + 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); + +out: + mutex_unlock(&group->trigger_lock); +} + static void record_times(struct psi_group_cpu *groupc, int cpu, bool memstall_tick) { @@ -460,8 +668,8 @@ static void record_times(struct psi_group_cpu *groupc, int cpu, groupc->times[PSI_NONIDLE] += delta; } -static void psi_group_change(struct psi_group *group, int cpu, - unsigned int clear, unsigned int set) +static u32 psi_group_change(struct psi_group *group, int cpu, + unsigned int clear, unsigned int set) { struct psi_group_cpu *groupc; unsigned int t, m; @@ -507,6 +715,8 @@ static void psi_group_change(struct psi_group *group, int cpu, groupc->state_mask = state_mask; write_seqcount_end(&groupc->seq); + + return state_mask; } static struct psi_group *iterate_groups(struct task_struct *task, void **iter) @@ -567,7 +777,11 @@ void psi_task_change(struct task_struct *task, int clear, int set) wake_clock = false; while ((group = iterate_groups(task, &iter))) { - psi_group_change(group, cpu, clear, set); + u32 state_mask = psi_group_change(group, cpu, clear, set); + + if (state_mask & group->poll_states) + psi_schedule_poll_work(group, 1); + if (wake_clock && !delayed_work_pending(&group->avgs_work)) schedule_delayed_work(&group->avgs_work, PSI_FREQ); } @@ -668,6 +882,8 @@ void psi_cgroup_free(struct cgroup *cgroup) 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"); } /** @@ -731,7 +947,7 @@ 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, NULL); + collect_percpu_times(group, PSI_AVGS, NULL); if (now >= group->avg_next_update) group->avg_next_update = update_averages(group, now); mutex_unlock(&group->avgs_lock); @@ -743,7 +959,8 @@ int psi_show(struct seq_file *m, struct psi_group *group, enum psi_res res) for (w = 0; w < 3; w++) avg[w] = group->avg[res * 2 + full][w]; - total = div_u64(group->total[res * 2 + full], NSEC_PER_USEC); + 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", @@ -786,25 +1003,270 @@ 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 *t; + enum psi_states state; + u32 threshold_us; + u32 window_us; + + if (static_branch_likely(&psi_disabled)) + return ERR_PTR(-EOPNOTSUPP); + + 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) + state = PSI_IO_FULL + res * 2; + else + return ERR_PTR(-EINVAL); + + if (state >= PSI_NONIDLE) + return ERR_PTR(-EINVAL); + + if (window_us < WINDOW_MIN_US || + window_us > WINDOW_MAX_US) + return ERR_PTR(-EINVAL); + + /* Check threshold */ + if (threshold_us == 0 || threshold_us > window_us) + return ERR_PTR(-EINVAL); + + t = kmalloc(sizeof(*t), GFP_KERNEL); + if (!t) + return ERR_PTR(-ENOMEM); + + t->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); + + 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 = MAX_RT_PRIO - 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); + } + sched_setscheduler(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); + + mutex_unlock(&group->trigger_lock); + + return t; +} + +static void psi_trigger_destroy(struct kref *ref) +{ + struct psi_trigger *t = container_of(ref, struct psi_trigger, refcount); + struct psi_group *group = t->group; + struct kthread_worker *kworker_to_destroy = NULL; + + if (static_branch_likely(&psi_disabled)) + return; + + /* + * Wakeup waiters to stop polling. 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); + } + } + + 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 + */ + synchronize_rcu(); + /* + * Destroy the kworker after releasing trigger_lock to prevent a + * deadlock while waiting for psi_poll_work to acquire trigger_lock + */ + if (kworker_to_destroy) { + kthread_cancel_delayed_work_sync(&group->poll_work); + kthread_destroy_worker(kworker_to_destroy); + } + 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) +{ + __poll_t ret = DEFAULT_POLLMASK; + struct psi_trigger *t; + + 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(); + return DEFAULT_POLLMASK | EPOLLERR | EPOLLPRI; + } + kref_get(&t->refcount); + + rcu_read_unlock(); + + 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; +} + +static ssize_t psi_write(struct file *file, const char __user *user_buf, + size_t nbytes, enum psi_res res) +{ + char buf[32]; + size_t buf_size; + struct seq_file *seq; + struct psi_trigger *new; + + if (static_branch_likely(&psi_disabled)) + return -EOPNOTSUPP; + + buf_size = min(nbytes, (sizeof(buf) - 1)); + if (copy_from_user(buf, user_buf, buf_size)) + return -EFAULT; + + 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); + mutex_unlock(&seq->lock); + + return nbytes; +} + +static ssize_t psi_io_write(struct file *file, const char __user *user_buf, + size_t nbytes, loff_t *ppos) +{ + return psi_write(file, user_buf, nbytes, PSI_IO); +} + +static ssize_t psi_memory_write(struct file *file, const char __user *user_buf, + size_t nbytes, loff_t *ppos) +{ + return psi_write(file, user_buf, nbytes, PSI_MEM); +} + +static ssize_t psi_cpu_write(struct file *file, const char __user *user_buf, + size_t nbytes, loff_t *ppos) +{ + return psi_write(file, user_buf, nbytes, PSI_CPU); +} + +static __poll_t psi_fop_poll(struct file *file, poll_table *wait) +{ + struct seq_file *seq = file->private_data; + + return psi_trigger_poll(&seq->private, file, wait); +} + +static int psi_fop_release(struct inode *inode, struct file *file) +{ + struct seq_file *seq = file->private_data; + + psi_trigger_replace(&seq->private, NULL); + return single_release(inode, file); +} + static const struct file_operations psi_io_fops = { .open = psi_io_open, .read = seq_read, .llseek = seq_lseek, - .release = single_release, + .write = psi_io_write, + .poll = psi_fop_poll, + .release = psi_fop_release, }; static const struct file_operations psi_memory_fops = { .open = psi_memory_open, .read = seq_read, .llseek = seq_lseek, - .release = single_release, + .write = psi_memory_write, + .poll = psi_fop_poll, + .release = psi_fop_release, }; static const struct file_operations psi_cpu_fops = { .open = psi_cpu_open, .read = seq_read, .llseek = seq_lseek, - .release = single_release, + .write = psi_cpu_write, + .poll = psi_fop_poll, + .release = psi_fop_release, }; static int __init psi_proc_init(void) |