Re: RFR: 8257967: JFR: Events for loaded agents [v14]
On Fri, 31 Mar 2023 03:05:31 GMT, David Holmes wrote:
>> Markus Grönlund has updated the pull request incrementally with one
>> additional commit since the last revision:
>>
>> restore misssing frees
>
> src/hotspot/share/prims/agent.cpp line 533:
>
>> 531: if (thread->is_pending_jni_exception_check()) {
>> 532: thread->clear_pending_jni_exception_check();
>> 533: }
>
> Unsure why we pretend the agent checked this - don't we want -Xcheck:jni to
> report a bug in the agent?
Good question - I don't know. For dynamically loaded agents, there seems to be
quite a lot of handling to return a JNI_OK, even though the agent failed to
load or returned failure from the Agent_OnAttach. e.g.
// Agent_OnAttach executed so completion status is JNI_OK
return JNI_OK;
-
PR Review Comment: https://git.openjdk.org/jdk/pull/12923#discussion_r1154346856
Re: RFR: 8257967: JFR: Events for loaded agents [v14]
On Thu, 30 Mar 2023 19:20:11 GMT, Markus Grönlund wrote:
>> Greetings,
>>
>> We are adding support to let JFR report on Agents.
>>
>> Design
>>
>> An Agent is a library that uses any instrumentation or profiling APIs. Most
>> agents are started and initialized on the command line, but agents can also
>> be loaded dynamically during runtime. Because command line agents initialize
>> during the VM startup sequence, they add to the overall startup time latency
>> in getting the VM ready. The events will report on the time the agent took
>> to initialize.
>>
>> A JavaAgent is an agent written in the Java programming language, using the
>> APIs in the package
>> [java.lang.instrument](https://docs.oracle.com/en/java/javase/19/docs/api/java.instrument/java/lang/instrument/package-summary.html)
>>
>> A JavaAgent is sometimes called a JPLIS agent, where the acronym JPLIS
>> stands for Java Programming Language Instrumentation Services.
>>
>> To report on JavaAgents, JFR will add the new event type jdk.JavaAgent and
>> events will look similar to these two examples:
>>
>> // Command line
>> jdk.JavaAgent {
>> startTime = 12:31:19.789 (2023-03-08)
>> name = "JavaAgent.jar"
>> options = "foo=bar"
>> dynamic = false
>> initializationTime = 12:31:15.574 (2023-03-08)
>> initializationDuration = 172 ms
>> }
>>
>> // Dynamic load
>> jdk.JavaAgent {
>> startTime = 12:31:31.158 (2023-03-08)
>> name = "JavaAgent.jar"
>> options = "bar=baz"
>> dynamic = true
>> initializationTime = 12:31:31.037 (2023-03-08)
>> initializationDuration = 64,1 ms
>> }
>>
>> The jdk.JavaAgent event type is a JFR periodic event that iterates over
>> running Java agents.
>>
>> For a JavaAgent event, the agent's name will be the specific .jar file
>> containing the instrumentation code. The options will be the specific
>> options passed to the .jar file as part of launching the agent, for example,
>> on the command line: -javaagent: JavaAgent.jar=foo=bar.
>>
>> The "dynamic" field denotes if the agent was loaded via the command line
>> (dynamic = false) or dynamically (dynamic = true)
>>
>> "initializationTime" is the timestamp the JVM invoked the initialization
>> method, and "initializationDuration" is the duration of executing the
>> initialization method.
>>
>> "startTime" represents the time the JFR framework issued the periodic event;
>> hence "initializationTime" will be earlier than "startTime".
>>
>> An agent can also be written in a native programming language using the [JVM
>> Tools Interface
>> (JVMTI)](https://docs.oracle.com/en/java/javase/19/docs/specs/jvmti.html).
>> This kind of agent, sometimes called a native agent, is a platform-specific
>> binary, sometimes referred to as a library, but here it means a .so or .dll
>> file.
>>
>> To report on native agents, JFR will add the new event type jdk.NativeAgent
>> and events will look similar to this example:
>>
>> jdk.NativeAgent {
>> startTime = 12:31:40.398 (2023-03-08)
>> name = "jdwp"
>> options = "transport=dt_socket,server=y,address=any,onjcmd=y"
>> dynamic = false
>> initializationTime = 12:31:36.142 (2023-03-08)
>> initializationDuration = 0,00184 ms
>> path =
>> "c:\ade\github\openjdk\jdk\build\windows-x86_64-server-slowdebug\jdk\bin\jdwp.dll"
>> }
>>
>> The layout of the event type is very similar to the jdk.JavaAgent event, but
>> here the path to the native library is reported.
>>
>> The initialization of a native agent is performed by invoking an
>> agent-specified callback routine. The "initializationTime" is when the JVM
>> sent or would have sent the JVMTI VMInit event to a specified callback.
>> "initializationDuration" is the duration to execute that specific callback.
>> If no callback is specified for the JVMTI VMInit event, the
>> "initializationDuration" will be 0. If the agent is loaded dynamically,
>> "initializationDuration" is the time taken to execute the Agent_OnAttach
>> callback.
>>
>> Implementation
>>
>> There has not existed a reification of a JavaAgent directly in the JVM, as
>> these are built on top of the JDK native library, "instrument", using a
>> many-to-one mapping. At the level of the JVM, the only representation of
>> agents after startup is through JvmtiEnv's, which agents request from the
>> JVM during startup and initialization — as such, mapping which JvmtiEnv
>> belongs to what JavaAgent was not possible before.
>>
>> Using implementation details of how the JDK native library "instrument"
>> interacts with the JVM, we can build this mapping to track what JvmtiEnv's
>> "belong" to what JavaAgent. This mapping now lets us report the
>> Java-relevant context (name, options) and measure the time it takes for the
>> JavaAgent to initialize.
>>
>> When implementing this capability, it was necessary to refactor the code
>> used to represent agents, AgentLibrary. The previous implementation was
>> located primarily in arguments.cpp, a
Re: RFR: 8257967: JFR: Events for loaded agents [v14]
On Thu, 30 Mar 2023 19:20:11 GMT, Markus Grönlund wrote:
>> Greetings,
>>
>> We are adding support to let JFR report on Agents.
>>
>> Design
>>
>> An Agent is a library that uses any instrumentation or profiling APIs. Most
>> agents are started and initialized on the command line, but agents can also
>> be loaded dynamically during runtime. Because command line agents initialize
>> during the VM startup sequence, they add to the overall startup time latency
>> in getting the VM ready. The events will report on the time the agent took
>> to initialize.
>>
>> A JavaAgent is an agent written in the Java programming language, using the
>> APIs in the package
>> [java.lang.instrument](https://docs.oracle.com/en/java/javase/19/docs/api/java.instrument/java/lang/instrument/package-summary.html)
>>
>> A JavaAgent is sometimes called a JPLIS agent, where the acronym JPLIS
>> stands for Java Programming Language Instrumentation Services.
>>
>> To report on JavaAgents, JFR will add the new event type jdk.JavaAgent and
>> events will look similar to these two examples:
>>
>> // Command line
>> jdk.JavaAgent {
>> startTime = 12:31:19.789 (2023-03-08)
>> name = "JavaAgent.jar"
>> options = "foo=bar"
>> dynamic = false
>> initialization = 12:31:15.574 (2023-03-08)
>> initializationTime = 172 ms
>> }
>>
>> // Dynamic load
>> jdk.JavaAgent {
>> startTime = 12:31:31.158 (2023-03-08)
>> name = "JavaAgent.jar"
>> options = "bar=baz"
>> dynamic = true
>> initialization = 12:31:31.037 (2023-03-08)
>> initializationTime = 64,1 ms
>> }
>>
>> The jdk.JavaAgent event type is a JFR periodic event that iterates over
>> running Java agents.
>>
>> For a JavaAgent event, the agent's name will be the specific .jar file
>> containing the instrumentation code. The options will be the specific
>> options passed to the .jar file as part of launching the agent, for example,
>> on the command line: -javaagent: JavaAgent.jar=foo=bar.
>>
>> The "dynamic" field denotes if the agent was loaded via the command line
>> (dynamic = false) or dynamically (dynamic = true)
>>
>> "initialization" is the timestamp the JVM invoked the initialization method,
>> and "initializationTime" is the duration of executing the initialization
>> method.
>>
>> "startTime" represents the time the JFR framework issued the periodic event;
>> hence "initialization" will be earlier than "startTime".
>>
>> An agent can also be written in a native programming language using the [JVM
>> Tools Interface
>> (JVMTI)](https://docs.oracle.com/en/java/javase/19/docs/specs/jvmti.html).
>> This kind of agent, sometimes called a native agent, is a platform-specific
>> binary, sometimes referred to as a library, but here it means a .so or .dll
>> file.
>>
>> To report on native agents, JFR will add the new event type jdk.NativeAgent
>> and events will look similar to this example:
>>
>> jdk.NativeAgent {
>> startTime = 12:31:40.398 (2023-03-08)
>> name = "jdwp"
>> options = "transport=dt_socket,server=y,address=any,onjcmd=y"
>> dynamic = false
>> initialization = 12:31:36.142 (2023-03-08)
>> initializationTime = 0,00184 ms
>> path =
>> "c:\ade\github\openjdk\jdk\build\windows-x86_64-server-slowdebug\jdk\bin\jdwp.dll"
>> }
>>
>> The layout of the event type is very similar to the jdk.JavaAgent event, but
>> here the path to the native library is reported.
>>
>> The initialization of a native agent is performed by invoking an
>> agent-specified callback routine. The "initialization" is when the JVM sent
>> or would have sent the JVMTI VMInit event to a specified callback.
>> "initializationTime" is the duration to execute that specific callback. If
>> no callback is specified for the JVMTI VMInit event, the
>> "initializationTime" will be 0.
>>
>> Implementation
>>
>> There has not existed a reification of a JavaAgent directly in the JVM, as
>> these are built on top of the JDK native library, "instrument", using a
>> many-to-one mapping. At the level of the JVM, the only representation of
>> agents after startup is through JvmtiEnv's, which agents request from the
>> JVM during startup and initialization — as such, mapping which JvmtiEnv
>> belongs to what JavaAgent was not possible before.
>>
>> Using implementation details of how the JDK native library "instrument"
>> interacts with the JVM, we can build this mapping to track what JvmtiEnv's
>> "belong" to what JavaAgent. This mapping now lets us report the
>> Java-relevant context (name, options) and measure the time it takes for the
>> JavaAgent to initialize.
>>
>> When implementing this capability, it was necessary to refactor the code
>> used to represent agents, AgentLibrary. The previous implementation was
>> located primarily in arguments.cpp, and threads.cpp but also jvmtiExport.cpp.
>>
>> The refactoring isolates the relevant logic into two new modules,
>> prims/agent.hpp and prims/agentList.hpp. Breaking out thi
Re: RFR: 8257967: JFR: Events for loaded agents [v14]
> Greetings,
>
> We are adding support to let JFR report on Agents.
>
> Design
>
> An Agent is a library that uses any instrumentation or profiling APIs. Most
> agents are started and initialized on the command line, but agents can also
> be loaded dynamically during runtime. Because command line agents initialize
> during the VM startup sequence, they add to the overall startup time latency
> in getting the VM ready. The events will report on the time the agent took to
> initialize.
>
> A JavaAgent is an agent written in the Java programming language, using the
> APIs in the package
> [java.lang.instrument](https://docs.oracle.com/en/java/javase/19/docs/api/java.instrument/java/lang/instrument/package-summary.html)
>
> A JavaAgent is sometimes called a JPLIS agent, where the acronym JPLIS stands
> for Java Programming Language Instrumentation Services.
>
> To report on JavaAgents, JFR will add the new event type jdk.JavaAgent and
> events will look similar to these two examples:
>
> // Command line
> jdk.JavaAgent {
> startTime = 12:31:19.789 (2023-03-08)
> name = "JavaAgent.jar"
> options = "foo=bar"
> dynamic = false
> initialization = 12:31:15.574 (2023-03-08)
> initializationTime = 172 ms
> }
>
> // Dynamic load
> jdk.JavaAgent {
> startTime = 12:31:31.158 (2023-03-08)
> name = "JavaAgent.jar"
> options = "bar=baz"
> dynamic = true
> initialization = 12:31:31.037 (2023-03-08)
> initializationTime = 64,1 ms
> }
>
> The jdk.JavaAgent event type is a JFR periodic event that iterates over
> running Java agents.
>
> For a JavaAgent event, the agent's name will be the specific .jar file
> containing the instrumentation code. The options will be the specific options
> passed to the .jar file as part of launching the agent, for example, on the
> command line: -javaagent: JavaAgent.jar=foo=bar.
>
> The "dynamic" field denotes if the agent was loaded via the command line
> (dynamic = false) or dynamically (dynamic = true)
>
> "initialization" is the timestamp the JVM invoked the initialization method,
> and "initializationTime" is the duration of executing the initialization
> method.
>
> "startTime" represents the time the JFR framework issued the periodic event;
> hence "initialization" will be earlier than "startTime".
>
> An agent can also be written in a native programming language using the [JVM
> Tools Interface
> (JVMTI)](https://docs.oracle.com/en/java/javase/19/docs/specs/jvmti.html).
> This kind of agent, sometimes called a native agent, is a platform-specific
> binary, sometimes referred to as a library, but here it means a .so or .dll
> file.
>
> To report on native agents, JFR will add the new event type jdk.NativeAgent
> and events will look similar to this example:
>
> jdk.NativeAgent {
> startTime = 12:31:40.398 (2023-03-08)
> name = "jdwp"
> options = "transport=dt_socket,server=y,address=any,onjcmd=y"
> dynamic = false
> initialization = 12:31:36.142 (2023-03-08)
> initializationTime = 0,00184 ms
> path =
> "c:\ade\github\openjdk\jdk\build\windows-x86_64-server-slowdebug\jdk\bin\jdwp.dll"
> }
>
> The layout of the event type is very similar to the jdk.JavaAgent event, but
> here the path to the native library is reported.
>
> The initialization of a native agent is performed by invoking an
> agent-specified callback routine. The "initialization" is when the JVM sent
> or would have sent the JVMTI VMInit event to a specified callback.
> "initializationTime" is the duration to execute that specific callback. If no
> callback is specified for the JVMTI VMInit event, the "initializationTime"
> will be 0.
>
> Implementation
>
> There has not existed a reification of a JavaAgent directly in the JVM, as
> these are built on top of the JDK native library, "instrument", using a
> many-to-one mapping. At the level of the JVM, the only representation of
> agents after startup is through JvmtiEnv's, which agents request from the JVM
> during startup and initialization — as such, mapping which JvmtiEnv belongs
> to what JavaAgent was not possible before.
>
> Using implementation details of how the JDK native library "instrument"
> interacts with the JVM, we can build this mapping to track what JvmtiEnv's
> "belong" to what JavaAgent. This mapping now lets us report the Java-relevant
> context (name, options) and measure the time it takes for the JavaAgent to
> initialize.
>
> When implementing this capability, it was necessary to refactor the code used
> to represent agents, AgentLibrary. The previous implementation was located
> primarily in arguments.cpp, and threads.cpp but also jvmtiExport.cpp.
>
> The refactoring isolates the relevant logic into two new modules,
> prims/agent.hpp and prims/agentList.hpp. Breaking out this code from their
> older places will help reduce the sizes of oversized arguments.cpp and
> threads.cpp.
>
> The previous two lists that maintained "agents" (JVMTI) and
