/* SPDX-License-Identifier: GPL-2.0-or-later */
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/*
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*
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* Authors: Waiman Long <longman@redhat.com>
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*/
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#include "lock_events.h"
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#ifdef CONFIG_LOCK_EVENT_COUNTS
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#ifdef CONFIG_PARAVIRT_SPINLOCKS
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/*
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* Collect pvqspinlock locking event counts
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*/
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#include <linux/sched.h>
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#include <linux/sched/clock.h>
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#include <linux/fs.h>
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#define EVENT_COUNT(ev) lockevents[LOCKEVENT_ ## ev]
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/*
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* PV specific per-cpu counter
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*/
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static DEFINE_PER_CPU(u64, pv_kick_time);
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/*
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* Function to read and return the PV qspinlock counts.
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*
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* The following counters are handled specially:
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* 1. pv_latency_kick
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* Average kick latency (ns) = pv_latency_kick/pv_kick_unlock
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* 2. pv_latency_wake
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* Average wake latency (ns) = pv_latency_wake/pv_kick_wake
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* 3. pv_hash_hops
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* Average hops/hash = pv_hash_hops/pv_kick_unlock
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*/
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ssize_t lockevent_read(struct file *file, char __user *user_buf,
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size_t count, loff_t *ppos)
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{
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char buf[64];
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int cpu, id, len;
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u64 sum = 0, kicks = 0;
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/*
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* Get the counter ID stored in file->f_inode->i_private
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*/
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id = (long)file_inode(file)->i_private;
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if (id >= lockevent_num)
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return -EBADF;
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for_each_possible_cpu(cpu) {
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sum += per_cpu(lockevents[id], cpu);
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/*
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* Need to sum additional counters for some of them
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*/
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switch (id) {
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case LOCKEVENT_pv_latency_kick:
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case LOCKEVENT_pv_hash_hops:
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kicks += per_cpu(EVENT_COUNT(pv_kick_unlock), cpu);
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break;
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case LOCKEVENT_pv_latency_wake:
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kicks += per_cpu(EVENT_COUNT(pv_kick_wake), cpu);
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break;
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}
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}
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if (id == LOCKEVENT_pv_hash_hops) {
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u64 frac = 0;
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if (kicks) {
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frac = 100ULL * do_div(sum, kicks);
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frac = DIV_ROUND_CLOSEST_ULL(frac, kicks);
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}
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/*
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* Return a X.XX decimal number
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*/
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len = snprintf(buf, sizeof(buf) - 1, "%llu.%02llu\n",
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sum, frac);
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} else {
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/*
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* Round to the nearest ns
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*/
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if ((id == LOCKEVENT_pv_latency_kick) ||
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(id == LOCKEVENT_pv_latency_wake)) {
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if (kicks)
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sum = DIV_ROUND_CLOSEST_ULL(sum, kicks);
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}
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len = snprintf(buf, sizeof(buf) - 1, "%llu\n", sum);
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}
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return simple_read_from_buffer(user_buf, count, ppos, buf, len);
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}
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/*
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* PV hash hop count
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*/
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static inline void lockevent_pv_hop(int hopcnt)
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{
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this_cpu_add(EVENT_COUNT(pv_hash_hops), hopcnt);
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}
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/*
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* Replacement function for pv_kick()
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*/
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static inline void __pv_kick(int cpu)
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{
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u64 start = sched_clock();
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per_cpu(pv_kick_time, cpu) = start;
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pv_kick(cpu);
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this_cpu_add(EVENT_COUNT(pv_latency_kick), sched_clock() - start);
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}
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/*
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* Replacement function for pv_wait()
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*/
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static inline void __pv_wait(u8 *ptr, u8 val)
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{
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u64 *pkick_time = this_cpu_ptr(&pv_kick_time);
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*pkick_time = 0;
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pv_wait(ptr, val);
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if (*pkick_time) {
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this_cpu_add(EVENT_COUNT(pv_latency_wake),
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sched_clock() - *pkick_time);
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lockevent_inc(pv_kick_wake);
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}
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}
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#define pv_kick(c) __pv_kick(c)
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#define pv_wait(p, v) __pv_wait(p, v)
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#endif /* CONFIG_PARAVIRT_SPINLOCKS */
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#else /* CONFIG_LOCK_EVENT_COUNTS */
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static inline void lockevent_pv_hop(int hopcnt) { }
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#endif /* CONFIG_LOCK_EVENT_COUNTS */
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