async-profiler可以跟踪以下类型的事件：
- CPU性能分析
- 硬件和软件性能计数器，比如缓存遗漏、分支遗漏、页面错误、上下文切换等等。
- Java堆中的分配
- 满足锁尝试，包括Java对象监视器和重入锁
如何使用：
[root@mvxl52738 async-profiler]# ./profiler.sh
Usage: ./profiler.sh [action] [options]
Actions:
start 开始分析并立即返回
stop 停止分析
status 打印分析状态
list 目标JVM支持的列表分析事件
collect 在指定的时间内收集概要文件然后停止（默认动作）
Options:
-e event 分析事件: cpu|alloc|lock|cache-misses etc.
-d duration 分析持续时间，以秒为单位
-f filename 将输出转储到文件
-i interval 采样间隔，纳秒
-j jstackdepth 最大Java栈深度
-b bufsize 帧缓冲区大小
-t 每一个堆栈跟踪都将以一个线程处理
-s 简单的类名而不是FQN
-o fmt[,fmt...] 输出格式: summary|traces|flat|collapsed|svg|tree|jfr
示例: ./profiler.sh -d 30 -f profile.svg 3456
./profiler.sh start -i 999000 jps
./profiler.sh stop -o summary,flat jps
在Linux 4.6中，使用来自非根进程的perf_events来捕获内核调用堆栈需要设置两个运行时变量。您可以使用sysctl设置它们，或者如下所示：
# perf_event_paranoid用于限制访问性能计数器的权限
# 0：仅允许访问用户空间的性能计数器
# 1：内核与用户空间的性能计数器都可以访问
# 2：仅允许访问特殊的CPU数据(不包括跟踪点)
# -1：不限制
[root@mvxl52738 ~]# echo 1 > /proc/sys/kernel/perf_event_paranoid
# 是否启用kptr_restrice，此功能为安全性功能，用于屏蔽内核指针。
# 0：该特性被完全禁止;
[root@mvxl52738 ~]# echo 0 > /proc/sys/kernel/kptr_restrict
CPU性能分析
# 默认情况下，分析频率是100赫兹（每10毫秒的CPU时间）。下面是打印到Java应用程序终端的输出示例：
[root@mvxl52738 async-profiler]# ./profiler.sh start 57951
[root@mvxl52738 async-profiler]# ./profiler.sh stop 57951
--- Execution profile ---
Total samples: 3
Non-Java: 1 (33.33%)
Frame buffer usage: 0.0026%
--- 10492147 ns (33.57%), 1 sample
[ 0] finish_task_switch_[k]
[ 1] __schedule_[k]
[ 2] schedule_[k]
[ 3] futex_wait_queue_me_[k]
[ 4] futex_wait_[k]
[ 5] do_futex_[k]
[ 6] sys_futex_[k]
[ 7] system_call_fastpath_[k]
[ 8] pthread_cond_timedwait@@GLIBC_2.3.2
[ 9] os::sleep(Thread*, long, bool)
[10] JVM_Sleep
[11] java.lang.Thread.sleep
[12] com.alibaba.dubbo.remoting.exchange.support.DefaultFuture$RemotingInvocationTimeoutScan.run
[13] java.lang.Thread.run
--- 10407032 ns (33.30%), 1 sample
[ 0] java_lang_Thread::set_thread_status(oopDesc*, java_lang_Thread::ThreadStatus)
[ 1] java.lang.Thread.sleep
[ 2] com.alibaba.dubbo.remoting.exchange.support.DefaultFuture$RemotingInvocationTimeoutScan.run
[ 3] java.lang.Thread.run
--- 10351666 ns (33.12%), 1 sample
[ 0] CompactibleFreeListSpace::free() const
[ 1] CompactibleFreeListSpace::used() const
[ 2] PerfLongVariant::sample()
[ 3] StatSamplerTask::task()
[ 4] PeriodicTask::real_time_tick(int)
[ 5] WatcherThread::run()
[ 6] java_start(Thread*)
[ 7] start_thread
ns percent samples top
---------- ------- ------- ---
10492147 33.57% 1 finish_task_switch_[k]
10407032 33.30% 1 java_lang_Thread::set_thread_status(oopDesc*, java_lang_Thread::ThreadStatus)
10351666 33.12% 1 CompactibleFreeListSpace::free() const
# 或者
[root@mvxl52738 async-profiler]# ./profiler.sh -d 30 57951
锁对象查看 -e lock
类型对象生成统计 -e alloc
[root@mvxl52738 async-profiler]# ./profiler.sh start -e alloc 57951
Started [alloc] profiling
[root@mvxl52738 async-profiler]# ./profiler.sh stop -e alloc 57951
--- Execution profile ---
Total samples: 5
Frame buffer usage: 0.0062%
--- 2798312 bytes (56.41%), 1 sample
[ 0] byte[]
[ 1] java.lang.StringCoding$StringEncoder.encode
[ 2] java.lang.StringCoding.encode
[ 3] java.lang.StringCoding.encode
[ 4] java.lang.String.getBytes
[ 5] com.alibaba.rocketmq.remoting.protocol.RemotingSerializable.encode
[ 6] com.alibaba.rocketmq.client.impl.MQClientAPIImpl.sendHearbeat
[ 7] com.alibaba.rocketmq.client.impl.factory.MQClientInstance.sendHeartbeatToAllBroker
[ 8] com.alibaba.rocketmq.client.impl.factory.MQClientInstance.sendHeartbeatToAllBrokerWithLock
[ 9] com.alibaba.rocketmq.client.impl.factory.MQClientInstance$4.run
[10] java.util.concurrent.Executors$RunnableAdapter.call
[11] java.util.concurrent.FutureTask.runAndReset
[12] java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301
[13] java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run
[14] java.util.concurrent.ThreadPoolExecutor.runWorker
[15] java.util.concurrent.ThreadPoolExecutor$Worker.run
[16] java.lang.Thread.run
--- 1610928 bytes (32.48%), 3 samples
[ 0] char[]
[ 1] java.lang.AbstractStringBuilder.
[ 2] java.lang.StringBuilder.
[ 3] com.alibaba.dubbo.remoting.transport.DecodeHandler.decode
[ 4] com.alibaba.dubbo.remoting.transport.DecodeHandler.received
[ 5] com.alibaba.dubbo.remoting.transport.dispatcher.ChannelEventRunnable.run
[ 6] java.util.concurrent.ThreadPoolExecutor.runWorker
[ 7] java.util.concurrent.ThreadPoolExecutor$Worker.run
[ 8] java.lang.Thread.run
--- 551112 bytes (11.11%), 1 sample
[ 0] char[]
[ 1] java.util.Arrays.copyOf
[ 2] java.lang.AbstractStringBuilder.ensureCapacityInternal
[ 3] java.lang.AbstractStringBuilder.append
[ 4] java.lang.StringBuilder.append
[ 5] com.meicloud.ecu.fc.impl.utils.RespPackUtil.execInvokeService
[ 6] com.meicloud.ecu.fc.impl.facade.impl.OrderReportFacadeImpl.selectItem
[ 7] com.alibaba.dubbo.common.bytecode.Wrapper4.invokeMethod
[ 8] com.alibaba.dubbo.rpc.proxy.javassist.JavassistProxyFactory$1.doInvoke
[ 9] com.alibaba.dubbo.rpc.proxy.AbstractProxyInvoker.invoke
[10] com.alibaba.dubbo.config.invoker.DelegateProviderMetaDataInvoker.invoke
[11] com.alibaba.dubbo.rpc.protocol.InvokerWrapper.invoke
[12] com.alibaba.dubbo.rpc.filter.ExceptionFilter.invoke
[13] com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke
[14] com.alibaba.dubbo.monitor.support.MonitorFilter.invoke
[15] com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke
[16] com.alibaba.dubbo.rpc.filter.TimeoutFilter.invoke
[17] com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke
[18] com.alibaba.dubbo.rpc.protocol.dubbo.filter.TraceFilter.invoke
[19] com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke
[20] com.alibaba.dubbo.rpc.filter.ContextFilter.invoke
[21] com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke
[22] com.alibaba.dubbo.rpc.filter.GenericFilter.invoke
[23] com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke
[24] com.alibaba.dubbo.rpc.filter.ClassLoaderFilter.invoke
[25] com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke
[26] com.alibaba.dubbo.rpc.filter.EchoFilter.invoke
[27] com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke
[28] com.alibaba.dubbo.rpc.protocol.dubbo.DubboProtocol$1.reply
[29] com.alibaba.dubbo.remoting.exchange.support.header.HeaderExchangeHandler.handleRequest
[30] com.alibaba.dubbo.remoting.exchange.support.header.HeaderExchangeHandler.received
[31] com.alibaba.dubbo.remoting.transport.DecodeHandler.received
[32] com.alibaba.dubbo.remoting.transport.dispatcher.ChannelEventRunnable.run
[33] java.util.concurrent.ThreadPoolExecutor.runWorker
[34] java.util.concurrent.ThreadPoolExecutor$Worker.run
[35] java.lang.Thread.run
bytes percent samples top
---------- ------- ------- ---
2798312 56.41% 1 byte[]
2162040 43.59% 4 char[]
作为java-agent启动
# event=alloc 代替 -e alloc , file=profile.svg 代替 -f profile.svg
java -agentpath:/tmp/async-profiler/build/libasyncProfiler.so=start,svg,file=profile.svg
可视化火焰图像
[root@mvxl52738 async-profiler]# ./profiler.sh -d 180 -f /tmp/flamegraph.svg 57951 --title fc
横条越长，代表占用的cpu时间是最多
火焰图