记录一次上下文切换次数的统计

如果要记录因为获取不到锁而切换线程可以用这个封装的锁替代

#pragma once

#include <mutex>

#include <atomic>

#include <iostream>

#include "logger.h"

class StatisticMutex {

std::mutex mtx;

std::atomic<size_t> contention_count{0}; // 统计竞争次数

public:

void enter() {

// 尝试非阻塞获取，若失败则记录竞争

if (!mtx.try_lock()) {

logInfo("NYX ++1 \n");

contention_count.fetch_add(1, std::memory_order_relaxed);

mtx.lock(); // 阻塞等待

}

bool try_lock() {

bool success = mtx.try_lock();

if (!success) {

contention_count.fetch_add(1, std::memory_order_relaxed);

}

return success;

}

void leave() {

mtx.unlock();

}

size_t get_contention_count() const {

return contention_count.load(std::memory_order_relaxed);

}

};

用这个脚本统计线程下线程切换的次数每秒

while true; do cat /proc/9759/status | grep ctxt_switches; sleep 1; done

/proc# while true; do cat /proc/9759/status | grep ctxt_switches; sleep 1; done

voluntary_ctxt_switches: 6384

nonvoluntary_ctxt_switches: 408

voluntary_ctxt_switches: 6393

nonvoluntary_ctxt_switches: 409

voluntary_ctxt_switches: 6403

nonvoluntary_ctxt_switches: 410

主动切换次数大约9次每秒大概有什么sleep 或者频繁的唤醒并且wait...

strace -e trace=nanosleep,futex,read,write -p 9759

strace: Process 9759 attached

通过strace发现确实有8次sleep 才想起是自己加的调试代码为了信标帧可以更频繁的发送让手机可以识别

futex(0x2e08ca50, FUTEX_WAIT_BITSET_PRIVATE|FUTEX_CLOCK_REALTIME, 0, NULL, FUTEX_BITSET_MATCH_ANY) = 0

write(1, " $2026-05-07 19:36:21.060491$ [97"..., 85) = 85

futex(0x2e12f6b0, FUTEX_WAKE_PRIVATE, 1) = 1

write(61, "\252U\220\0\0\0\224\0\200\0\0\0\377\377\377\377\377\3778\257)3DU8\257)3DU \375"..., 151) = 151