CPU时间即反映CPU全速工作时完成该进程所花费的时间
cpu时间计算CPU TIME = （# of CPU Clock Cycles） x Clock Period // “#” 表示消耗的CPU时钟周期个数
= (# of CPU Clock Cycles)/(Clock Frequency)
cpu时间计算 = （#个cpu时钟周期） X 电子脉冲时钟周期 （类似于晶振产生的脉冲，而频率就是单位时间产生脉冲数量 = 1/单个脉冲时钟周期占用时间）
= （#个cpu时钟周期） / 电子脉冲时钟频率
时间片-概述
举个多线程程序的例子，说明时间片是怎样工作的（java）
如上：
由此可见：两个线程是交替执行的（数字的变化），从宏观上（同时输出）。
以下是搜的资料：
1，什么是时间片轮转：
时间片轮转调度是一种最古老，最简单，最公平且使用最广的算法是时间片调度。每个进程被分配一个时间段，称作它的时间片，即该进程允许运行的时间。如果在 时间片结束时进程还在运行，则CPU将被剥夺并分配给另一个进程。如果进程在时间片结束前阻塞或结束，则CPU当即进行切换。调度程序所要做的就是维护一 张就绪进程列表，，当进程用完它的时间片后，它被移到队列的末尾。
时间片轮转调度中唯一有趣的一点是时间片的长度。从一个进程切换到另一个进程是需要一定时间的--保存和装入寄存器值及内存映像，更新各种表格和队列等。 假如进程切换(process switch) - 有时称为上下文切换(context switch)，需要5毫秒，再假设时间片设为20毫秒，则在 做完20毫秒有用的工作之后，CPU将花费5毫秒来进行进程切换。CPU时间的20%被浪费在了管理开销上。
为了提高CPU效率，我们可以将时间片设为500毫秒。这时浪费的时间只有1%。但考虑在一个分时系统中，如果有十个交互用户几乎同时按下回车键，将发生 什么情况？假设所有其他进程都用足它们的时间片的话，最后一个不幸的进程不得不等待5秒钟才获得运行机会。多数用户无法忍受一条简短命令要5秒钟才能做出 响应。同样的问题在一台支持多道程序的个人计算机上也会发生。
结论可以归结如下：时间片设得太短会导致过多的进程切换，降低了CPU效率；而设得太长又可能引起对短的交互请求的响应变差。将时间片设为100毫秒通常是一个比较合理的折衷。
举个多线程程序的例子，说明时间片是怎样工作的（java）
如上：
由此可见：两个线程是交替执行的（数字的变化），从宏观上（同时输出）。
以下是搜的资料：
1，什么是时间片轮转：
时间片轮转调度是一种最古老，最简单，最公平且使用最广的算法是时间片调度。每个进程被分配一个时间段，称作它的时间片，即该进程允许运行的时间。如果在 时间片结束时进程还在运行，则CPU将被剥夺并分配给另一个进程。如果进程在时间片结束前阻塞或结束，则CPU当即进行切换。调度程序所要做的就是维护一 张就绪进程列表，，当进程用完它的时间片后，它被移到队列的末尾。
时间片轮转调度中唯一有趣的一点是时间片的长度。从一个进程切换到另一个进程是需要一定时间的--保存和装入寄存器值及内存映像，更新各种表格和队列等。 假如进程切换(process switch) - 有时称为上下文切换(context switch)，需要5毫秒，再假设时间片设为20毫秒，则在 做完20毫秒有用的工作之后，CPU将花费5毫秒来进行进程切换。CPU时间的20%被浪费在了管理开销上。
为了提高CPU效率，我们可以将时间片设为500毫秒。这时浪费的时间只有1%。但考虑在一个分时系统中，如果有十个交互用户几乎同时按下回车键，将发生 什么情况？假设所有其他进程都用足它们的时间片的话，最后一个不幸的进程不得不等待5秒钟才获得运行机会。多数用户无法忍受一条简短命令要5秒钟才能做出 响应。同样的问题在一台支持多道程序的个人计算机上也会发生。
结论可以归结如下：时间片设得太短会导致过多的进程切换，降低了CPU效率；而设得太长又可能引起对短的交互请求的响应变差。将时间片设为100毫秒通常是一个比较合理的折衷。
CPU使用率：（Jconsole MBean java.lang.OperatingSystem.ProcessCpuTime ）
如何取得jvm实例的cpu占用
本文会贴很多代码，代码遵循Google的java代码格式。获取数据篇
１、jmx连接的创建是一个比较重的操作，我们使用apache的common pool2创建连接工厂。
public class JmxConnectionFactory implements KeyedPooledObjectFactory<JmxServer, JMXConnector> { @Override public PooledObject<JMXConnector> makeObject(JmxServer server) throws Exception { JMXServiceURL serviceURL = new JMXServiceURL(String.format( "service:jmx:rmi:///jndi/rmi://%s:%s/jmxrmi", server.getHost(), server.getPort())); Map<String, Object> environment = Maps.newHashMap(); String username = server.getUsername(); String password = server.getPassword(); if ((username != null) && (password != null)) { String[] credentials = new String[2]; credentials[0] = username; credentials[1] = password; environment.put(JMXConnector.CREDENTIALS, credentials); } environment.put("sun.rmi.transport.proxy.connectTimeout", 1000); environment.put("sun.rmi.transport.tcp.responseTimeout", 3000); JMXConnector connect = JMXConnectorFactory.connect(serviceURL, environment); return new DefaultPooledObject<JMXConnector>(connect); } @Override public void destroyObject(JmxServer key, PooledObject<JMXConnector> object) throws Exception { object.getObject().close(); } @Override public boolean validateObject(JmxServer key, PooledObject<JMXConnector> object) { JMXConnector connector = object.getObject(); try { connector.getConnectionId(); return true; } catch (IOException exception) { // ignore } return false; } @Override public void activateObject(JmxServer key, PooledObject<JMXConnector> p) throws Exception { } @Override public void passivateObject(JmxServer key, PooledObject<JMXConnector> p) throws Exception { } }
２、从连接池中获取JMX连接
private static GenericKeyedObjectPool<JmxServer, JMXConnector> POOL; private static AtomicInteger actives = new AtomicInteger(0); //.... try { JMXConnector connector = POOL.borrowObject(server); try { MBeanServerConnection mbsc = connector.getMBeanServerConnection(); // 在这个地方使用连接获取JVM的监控数据 // ...... } finally { POOL.returnObject(server, connector); }
3、计算cpu占用的逻辑是:
获取：ProcessCpuTime，Uptime，AvailableProcessors，然后结合上一次获取到的数据得出，算式为：
Math.min(99F, (ProcessCpuTime-PreProcessCpuTime) / ((Uptime-PreUptime) * 10000F * AvailableProcessors));
方式一：通过获取相应的Bean，然后通过Bean去获取数据
private long prevUpTime, prevProcessCpuTime; // ...... RuntimeMXBean runtimeMBean = newPlatformMXBeanProxy(mbsc, RUNTIME_MXBEAN_NAME, RuntimeMXBean.class); OperatingSystemMXBean operatingSystemMBean = newPlatformMXBeanProxy(mbsc, OPERATING_SYSTEM_MXBEAN_NAME, com.sun.management.OperatingSystemMXBean.class); int nCPUs = operatingSystemMBean.getAvailableProcessors(); if (runtimeMBean != null && operatingSystemMBean != null) { long uptime = runtimeMBean.getUptime(); long processCpuTime = operatingSystemMBean.getProcessCpuTime(); if (prevUpTime != 0 && prevProcessCpuTime != 0) { long elapsedCpu = processCpuTime - prevProcessCpuTime; long elaspedTime = uptime - prevUpTime; float cpuUsage = Math.min(99F, elapsedCpu / (elaspedTime * 10000F * nCPUs)); prevUpTime = uptime; prevProcessCpuTime = processCpuTime; // JsonObject value = new JsonObject(); String key = "CpuUsage"; LOGGER.debug("received value '{}%' for item '{}'", cpuUsage, key); value.addProperty(MonitorConst.JSON_TAG_VALUE, cpuUsage); value.addProperty(MonitorConst.JSON_TAG_NAME, key); return value; } else { prevUpTime = uptime; prevProcessCpuTime = processCpuTime; } } // ......
方式二、通过key来直接获取，代码通用些，比较长，代码参考zabbix gateway实现
// 通用获取方法 protected String getStringValue(MBeanServerConnection mbsc, String key) throws Exception { MonitorItem item = new MonitorItem(key); if (item.getKeyId().equals("jmx")) { if (2 != item.getArgumentCount()) { throw new MonitorException( "required key format: jmx[<object name>,<attribute name>]"); } ObjectName objectName = new ObjectName(item.getArgument(1)); String attributeName = item.getArgument(2); String realAttributeName; String fieldNames = ""; int sep; // // Attribute name and composite data field names are separated by dots. On the other hand the // name may contain a dot too. In this case user needs to escape it with a backslash. Also the // backslash symbols in the name must be escaped. So a real separator is unescaped dot and // separatorIndex() is used to locate it. // sep = HelperFunctionChest.separatorIndex(attributeName); if (-1 != sep) { LOGGER.trace("'{}' contains composite data", attributeName); realAttributeName = attributeName.substring(0, sep); fieldNames = attributeName.substring(sep + 1); } else { realAttributeName = attributeName; } // unescape possible dots or backslashes that were escaped by user realAttributeName = HelperFunctionChest.unescapeUserInput(realAttributeName); LOGGER.trace("attributeName:'{}'", realAttributeName); LOGGER.trace("fieldNames:'{}'", fieldNames); return getPrimitiveAttributeValue(mbsc.getAttribute(objectName, realAttributeName), fieldNames); } else if (item.getKeyId().equals("jmx.discovery")) { if (0 != item.getArgumentCount()) { throw new MonitorException("required key format: jmx.discovery"); } JsonArray counters = new JsonArray(); for (ObjectName name : mbsc.queryNames(null, null)) { LOGGER.trace("discovered object '{}'", name); for (MBeanAttributeInfo attrInfo : mbsc.getMBeanInfo(name).getAttributes()) { LOGGER.trace("discovered attribute '{}'", attrInfo.getName()); if (!attrInfo.isReadable()) { LOGGER.trace("attribute not readable, skipping"); continue; } try { LOGGER.trace("looking for attributes of primitive types"); String descr = (attrInfo.getName().equals(attrInfo.getDescription()) ? null : attrInfo .getDescription()); findPrimitiveAttributes(counters, name, descr, attrInfo.getName(), mbsc.getAttribute(name, attrInfo.getName())); } catch (Exception e) { Object[] logInfo = {name, attrInfo.getName(), e}; LOGGER.trace("processing '{},{}' failed", logInfo); } } } JsonObject mapping = new JsonObject(); mapping.add(MonitorConst.JSON_TAG_DATA, counters); return mapping.toString(); } else { throw new MonitorException("key ID '%s' is not supported", item.getKeyId()); } } private String getPrimitiveAttributeValue(Object dataObject, String fieldNames) throws MonitorException { LOGGER .trace("drilling down with data object '{}' and field names '{}'", dataObject, fieldNames); if (null == dataObject) { throw new MonitorException("data object is null"); } if (fieldNames.equals("")) { if (isPrimitiveAttributeType(dataObject.getClass())) { return dataObject.toString(); } else { throw new MonitorException( "data object type is not primitive: %s" + dataObject.getClass()); } } if (dataObject instanceof CompositeData) { LOGGER.trace("'{}' contains composite data", dataObject); CompositeData comp = (CompositeData) dataObject; String dataObjectName; String newFieldNames = ""; int sep = HelperFunctionChest.separatorIndex(fieldNames); if (-1 != sep) { dataObjectName = fieldNames.substring(0, sep); newFieldNames = fieldNames.substring(sep + 1); } else { dataObjectName = fieldNames; } // unescape possible dots or backslashes that were escaped by user dataObjectName = HelperFunctionChest.unescapeUserInput(dataObjectName); return getPrimitiveAttributeValue(comp.get(dataObjectName), newFieldNames); } else { throw new MonitorException("unsupported data object type along the path: %s", dataObject.getClass()); } } private void findPrimitiveAttributes(JsonArray counters, ObjectName name, String descr, String attrPath, Object attribute) { LOGGER.trace("drilling down with attribute path '{}'", attrPath); if (isPrimitiveAttributeType(attribute.getClass())) { LOGGER.trace("found attribute of a primitive type: {}", attribute.getClass()); JsonObject counter = new JsonObject(); counter.addProperty("{#JMXDESC}", null == descr ? name + "," + attrPath : descr); counter.addProperty("{#JMXOBJ}", name.toString()); counter.addProperty("{#JMXATTR}", attrPath); counter.addProperty("{#JMXTYPE}", attribute.getClass().getName()); counter.addProperty("{#JMXVALUE}", attribute.toString()); counters.add(counter); } else if (attribute instanceof CompositeData) { LOGGER.trace("found attribute of a composite type: {}", attribute.getClass()); CompositeData comp = (CompositeData) attribute; for (String key : comp.getCompositeType().keySet()) { findPrimitiveAttributes(counters, name, descr, attrPath + "." + key, comp.get(key)); } } else if (attribute instanceof TabularDataSupport || attribute.getClass().isArray()) { LOGGER.trace("found attribute of a known, unsupported type: {}", attribute.getClass()); } else { LOGGER .trace("found attribute of an unknown, unsupported type: {}", attribute.getClass()); } } private boolean isPrimitiveAttributeType(Class<?> clazz) { Class<?>[] clazzez = {Boolean.class, Character.class, Byte.class, Short.class, Integer.class, Long.class, Float.class, Double.class, String.class, java.math.BigDecimal.class, java.math.BigInteger.class, java.util.Date.class, ObjectName.class}; return HelperFunctionChest.arrayContains(clazzez, clazz); } // 使用示例 获取：ProcessCpuTime，Uptime，AvailableProcessors，然后结合上一次获取到的数据得出，算式为： String processCpuTime=getStringValue(mbsc, "jmx[\"java.lang:type=OperatingSystem\",ProcessCpuTime]") String uptime=getStringValue(mbsc, "jmx[\"java.lang:type=Runtime\",Uptime]", #1)-last("jmx[\"java.lang:type=Runtime\",Uptime]") String availableProcessors=getStringValue(mbsc, "jmx[\"java.lang:type=OperatingSystem\",AvailableProcessors]")
方式三、zabbix
１、clone一个Template JMX Generic，修改添加相应的item的配置，添加的Template JMX Consumer
<template> <template>Template JMX Consumer</template> <name>Template JMX Consumer</name> <groups> <group> <name>Templates</name> </group> </groups> <applications/> <items> <item> <name>AvailableProcessors</name> <type>16</type> <snmp_community/> <multiplier>0</multiplier> <snmp_oid/> <key>jmx["java.lang:type=OperatingSystem",AvailableProcessors]</key> <delay>60</delay> <history>7</history> <trends>365</trends> <status>0</status> <value_type>3</value_type> <allowed_hosts/> <units/> <delta>0</delta> <snmpv3_contextname/> <snmpv3_securityname/> <snmpv3_securitylevel>0</snmpv3_securitylevel> <snmpv3_authprotocol>0</snmpv3_authprotocol> <snmpv3_authpassphrase/> <snmpv3_privprotocol>0</snmpv3_privprotocol> <snmpv3_privpassphrase/> <formula>1</formula> <delay_flex/> <params/> <ipmi_sensor/> <data_type>0</data_type> <authtype>0</authtype> <username/> <password/> <publickey/> <privatekey/> <port/> <description/> <inventory_link>0</inventory_link> <applications> <application> <name>Operating System</name> </application> </applications> <valuemap/> </item> <item> <name>Cpu Usage</name> <type>15</type> <snmp_community/> <multiplier>0</multiplier> <snmp_oid/> <key>CpuUsage</key> <delay>30</delay> <history>7</history> <trends>365</trends> <status>0</status> <value_type>0</value_type> <allowed_hosts/> <units>%</units> <delta>0</delta> <snmpv3_contextname/> <snmpv3_securityname/> <snmpv3_securitylevel>0</snmpv3_securitylevel> <snmpv3_authprotocol>0</snmpv3_authprotocol> <snmpv3_authpassphrase/> <snmpv3_privprotocol>0</snmpv3_privprotocol> <snmpv3_privpassphrase/> <formula>1</formula> <delay_flex/> <params>(last("jmx[\"java.lang:type=OperatingSystem\",ProcessCpuTime]", #1)-last("jmx[\"java.lang:type=OperatingSystem\",ProcessCpuTime]", #2))/((last("jmx[\"java.lang:type=Runtime\",Uptime]", #1)-last("jmx[\"java.lang:type=Runtime\",Uptime]", #2))*10000*last("jmx[\"java.lang:type=OperatingSystem\",AvailableProcessors]", 0))</params> <ipmi_sensor/> <data_type>0</data_type> <authtype>0</authtype> <username/> <password/> <publickey/> <privatekey/> <port/> <description/> <inventory_link>0</inventory_link> <applications> <application> <name>Runtime</name> </application> </applications> <valuemap/> </item> <item> <name>ProcessCpuTime</name> <type>16</type> <snmp_community/> <multiplier>0</multiplier> <snmp_oid/> <key>jmx["java.lang:type=OperatingSystem",ProcessCpuTime]</key> <delay>60</delay> <history>7</history> <trends>365</trends> <status>0</status> <value_type>3</value_type> <allowed_hosts/> <units/> <delta>0</delta> <snmpv3_contextname/> <snmpv3_securityname/> <snmpv3_securitylevel>0</snmpv3_securitylevel> <snmpv3_authprotocol>0</snmpv3_authprotocol> <snmpv3_authpassphrase/> <snmpv3_privprotocol>0</snmpv3_privprotocol> <snmpv3_privpassphrase/> <formula>1</formula> <delay_flex/> <params/> <ipmi_sensor/> <data_type>0</data_type> <authtype>0</authtype> <username/> <password/> <publickey/> <privatekey/> <port/> <description/> <inventory_link>0</inventory_link> <applications> <application> <name>Operating System</name> </application> </applications> <valuemap/> </item> </items> <discovery_rules/> <macros/> <templates> <template> <name>Template JMX Generic</name> </template> </templates> <screens/> </template> // 修改原来的模板 <item> <name>jvm Uptime</name> <type>15</type> <snmp_community/> <multiplier>1</multiplier> <snmp_oid/> <key>jmxUptime</key> <delay>60</delay> <history>7</history> <trends>365</trends> <status>0</status> <value_type>3</value_type> <allowed_hosts/> <units>uptime</units> <delta>0</delta> <snmpv3_contextname/> <snmpv3_securityname/> <snmpv3_securitylevel>0</snmpv3_securitylevel> <snmpv3_authprotocol>0</snmpv3_authprotocol> <snmpv3_authpassphrase/> <snmpv3_privprotocol>0</snmpv3_privprotocol> <snmpv3_privpassphrase/> <formula>0.001</formula> <delay_flex/> <params>jmx["java.lang:type=Runtime",Uptime]</params> <ipmi_sensor/> <data_type>0</data_type> <authtype>0</authtype> <username/> <password/> <publickey/> <privatekey/> <port/> <description/> <inventory_link>0</inventory_link> <applications> <application> <name>Runtime</name> </application> </applications> <valuemap/> </item> <item> <name>jvm Uptime Microsecond</name> <type>16</type> <snmp_community/> <multiplier>0</multiplier> <snmp_oid/> <key>jmx["java.lang:type=Runtime",Uptime]</key> <delay>60</delay> <history>7</history> <trends>365</trends> <status>0</status> <value_type>3</value_type> <allowed_hosts/> <units>uptime</units> <delta>0</delta> <snmpv3_contextname/> <snmpv3_securityname/> <snmpv3_securitylevel>0</snmpv3_securitylevel> <snmpv3_authprotocol>0</snmpv3_authprotocol> <snmpv3_authpassphrase/> <snmpv3_privprotocol>0</snmpv3_privprotocol> <snmpv3_privpassphrase/> <formula>1</formula> <delay_flex/> <params/> <ipmi_sensor/> <data_type>0</data_type> <authtype>0</authtype> <username/> <password/> <publickey/> <privatekey/> <port/> <description/> <inventory_link>0</inventory_link> <applications> <application> <name>Runtime</name> </application> </applications> <valuemap/> </item>