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32927393dc
Instead of having all the sysctl handlers deal with user pointers, which is rather hairy in terms of the BPF interaction, copy the input to and from userspace in common code. This also means that the strings are always NUL-terminated by the common code, making the API a little bit safer. As most handler just pass through the data to one of the common handlers a lot of the changes are mechnical. Signed-off-by: Christoph Hellwig <hch@lst.de> Acked-by: Andrey Ignatov <rdna@fb.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
284 lines
7.2 KiB
C
284 lines
7.2 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* latencytop.c: Latency display infrastructure
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*
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* (C) Copyright 2008 Intel Corporation
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* Author: Arjan van de Ven <arjan@linux.intel.com>
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*/
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/*
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* CONFIG_LATENCYTOP enables a kernel latency tracking infrastructure that is
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* used by the "latencytop" userspace tool. The latency that is tracked is not
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* the 'traditional' interrupt latency (which is primarily caused by something
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* else consuming CPU), but instead, it is the latency an application encounters
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* because the kernel sleeps on its behalf for various reasons.
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*
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* This code tracks 2 levels of statistics:
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* 1) System level latency
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* 2) Per process latency
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*
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* The latency is stored in fixed sized data structures in an accumulated form;
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* if the "same" latency cause is hit twice, this will be tracked as one entry
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* in the data structure. Both the count, total accumulated latency and maximum
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* latency are tracked in this data structure. When the fixed size structure is
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* full, no new causes are tracked until the buffer is flushed by writing to
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* the /proc file; the userspace tool does this on a regular basis.
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*
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* A latency cause is identified by a stringified backtrace at the point that
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* the scheduler gets invoked. The userland tool will use this string to
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* identify the cause of the latency in human readable form.
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*
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* The information is exported via /proc/latency_stats and /proc/<pid>/latency.
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* These files look like this:
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*
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* Latency Top version : v0.1
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* 70 59433 4897 i915_irq_wait drm_ioctl vfs_ioctl do_vfs_ioctl sys_ioctl
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* | | | |
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* | | | +----> the stringified backtrace
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* | | +---------> The maximum latency for this entry in microseconds
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* | +--------------> The accumulated latency for this entry (microseconds)
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* +-------------------> The number of times this entry is hit
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*
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* (note: the average latency is the accumulated latency divided by the number
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* of times)
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*/
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#include <linux/kallsyms.h>
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#include <linux/seq_file.h>
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#include <linux/notifier.h>
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#include <linux/spinlock.h>
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#include <linux/proc_fs.h>
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#include <linux/latencytop.h>
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#include <linux/export.h>
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#include <linux/sched.h>
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#include <linux/sched/debug.h>
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#include <linux/sched/stat.h>
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#include <linux/list.h>
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#include <linux/stacktrace.h>
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static DEFINE_RAW_SPINLOCK(latency_lock);
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#define MAXLR 128
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static struct latency_record latency_record[MAXLR];
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int latencytop_enabled;
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void clear_tsk_latency_tracing(struct task_struct *p)
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{
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unsigned long flags;
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raw_spin_lock_irqsave(&latency_lock, flags);
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memset(&p->latency_record, 0, sizeof(p->latency_record));
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p->latency_record_count = 0;
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raw_spin_unlock_irqrestore(&latency_lock, flags);
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}
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static void clear_global_latency_tracing(void)
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{
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unsigned long flags;
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raw_spin_lock_irqsave(&latency_lock, flags);
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memset(&latency_record, 0, sizeof(latency_record));
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raw_spin_unlock_irqrestore(&latency_lock, flags);
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}
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static void __sched
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account_global_scheduler_latency(struct task_struct *tsk,
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struct latency_record *lat)
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{
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int firstnonnull = MAXLR + 1;
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int i;
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/* skip kernel threads for now */
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if (!tsk->mm)
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return;
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for (i = 0; i < MAXLR; i++) {
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int q, same = 1;
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/* Nothing stored: */
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if (!latency_record[i].backtrace[0]) {
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if (firstnonnull > i)
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firstnonnull = i;
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continue;
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}
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for (q = 0; q < LT_BACKTRACEDEPTH; q++) {
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unsigned long record = lat->backtrace[q];
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if (latency_record[i].backtrace[q] != record) {
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same = 0;
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break;
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}
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/* 0 entry marks end of backtrace: */
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if (!record)
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break;
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}
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if (same) {
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latency_record[i].count++;
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latency_record[i].time += lat->time;
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if (lat->time > latency_record[i].max)
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latency_record[i].max = lat->time;
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return;
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}
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}
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i = firstnonnull;
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if (i >= MAXLR - 1)
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return;
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/* Allocted a new one: */
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memcpy(&latency_record[i], lat, sizeof(struct latency_record));
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}
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/**
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* __account_scheduler_latency - record an occurred latency
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* @tsk - the task struct of the task hitting the latency
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* @usecs - the duration of the latency in microseconds
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* @inter - 1 if the sleep was interruptible, 0 if uninterruptible
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*
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* This function is the main entry point for recording latency entries
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* as called by the scheduler.
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*
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* This function has a few special cases to deal with normal 'non-latency'
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* sleeps: specifically, interruptible sleep longer than 5 msec is skipped
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* since this usually is caused by waiting for events via select() and co.
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*
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* Negative latencies (caused by time going backwards) are also explicitly
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* skipped.
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*/
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void __sched
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__account_scheduler_latency(struct task_struct *tsk, int usecs, int inter)
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{
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unsigned long flags;
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int i, q;
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struct latency_record lat;
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/* Long interruptible waits are generally user requested... */
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if (inter && usecs > 5000)
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return;
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/* Negative sleeps are time going backwards */
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/* Zero-time sleeps are non-interesting */
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if (usecs <= 0)
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return;
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memset(&lat, 0, sizeof(lat));
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lat.count = 1;
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lat.time = usecs;
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lat.max = usecs;
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stack_trace_save_tsk(tsk, lat.backtrace, LT_BACKTRACEDEPTH, 0);
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raw_spin_lock_irqsave(&latency_lock, flags);
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account_global_scheduler_latency(tsk, &lat);
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for (i = 0; i < tsk->latency_record_count; i++) {
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struct latency_record *mylat;
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int same = 1;
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mylat = &tsk->latency_record[i];
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for (q = 0; q < LT_BACKTRACEDEPTH; q++) {
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unsigned long record = lat.backtrace[q];
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if (mylat->backtrace[q] != record) {
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same = 0;
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break;
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}
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/* 0 entry is end of backtrace */
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if (!record)
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break;
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}
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if (same) {
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mylat->count++;
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mylat->time += lat.time;
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if (lat.time > mylat->max)
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mylat->max = lat.time;
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goto out_unlock;
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}
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}
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/*
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* short term hack; if we're > 32 we stop; future we recycle:
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*/
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if (tsk->latency_record_count >= LT_SAVECOUNT)
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goto out_unlock;
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/* Allocated a new one: */
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i = tsk->latency_record_count++;
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memcpy(&tsk->latency_record[i], &lat, sizeof(struct latency_record));
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out_unlock:
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raw_spin_unlock_irqrestore(&latency_lock, flags);
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}
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static int lstats_show(struct seq_file *m, void *v)
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{
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int i;
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seq_puts(m, "Latency Top version : v0.1\n");
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for (i = 0; i < MAXLR; i++) {
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struct latency_record *lr = &latency_record[i];
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if (lr->backtrace[0]) {
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int q;
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seq_printf(m, "%i %lu %lu",
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lr->count, lr->time, lr->max);
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for (q = 0; q < LT_BACKTRACEDEPTH; q++) {
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unsigned long bt = lr->backtrace[q];
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if (!bt)
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break;
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seq_printf(m, " %ps", (void *)bt);
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}
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seq_puts(m, "\n");
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}
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}
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return 0;
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}
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static ssize_t
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lstats_write(struct file *file, const char __user *buf, size_t count,
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loff_t *offs)
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{
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clear_global_latency_tracing();
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return count;
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}
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static int lstats_open(struct inode *inode, struct file *filp)
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{
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return single_open(filp, lstats_show, NULL);
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}
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static const struct proc_ops lstats_proc_ops = {
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.proc_open = lstats_open,
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.proc_read = seq_read,
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.proc_write = lstats_write,
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.proc_lseek = seq_lseek,
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.proc_release = single_release,
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};
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static int __init init_lstats_procfs(void)
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{
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proc_create("latency_stats", 0644, NULL, &lstats_proc_ops);
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return 0;
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}
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int sysctl_latencytop(struct ctl_table *table, int write, void *buffer,
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size_t *lenp, loff_t *ppos)
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{
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int err;
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err = proc_dointvec(table, write, buffer, lenp, ppos);
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if (latencytop_enabled)
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force_schedstat_enabled();
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return err;
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}
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device_initcall(init_lstats_procfs);
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