javavm | nowhere near finished but hey let | Interpreter library
kandi X-RAY | javavm Summary
kandi X-RAY | javavm Summary
Yeah so this is nowhere near finished but hey let's put it on the internet for people to look at. Be careful though. It's pretty bad in there and I don't want to be responsible for anyone going crazy.
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Top functions reviewed by kandi - BETA
- Registers the native resources
- Register native natives
- Registers native methods that are not supported
- Registers missing constants
- Initialization instructions
- Pop an operand from the stack
- Pushes a new JavaWrapper to the stack
- Registers the nativeatives hooks
- Opens a zip file
- Registers all non - nullatives of the network interfaces
- Register native Natives implementations
- Pop the instruction
- This method is called when the instruction is being executed
- Load java classes
- Called when a method is called
- Convert array to java value
- Evaluate the return type
- Full initialize method
- Updates the stack
- Registers native and native dispatches
- Evaluates the stack instruction
- Cast the current instruction into the stack
- Converts to string
- Execute the instruction
- Registers any local - host names that are available on the machine
- Registers allatives that are available in the JVM
javavm Key Features
javavm Examples and Code Snippets
Community Discussions
Trending Discussions on javavm
QUESTION
I am analyzing a performance issue on a Java servlet running on AdoptOpenJDK 11. The response time of the servlet slows down as the number of concurrent requests increases.
To isolate the cause of the issue, I had collected performance information with two tools while changing the number of concurrent requests:
- Windows Performance Monitor (to inspect CPU usage of the server)
- JDK Flight Recorder and JDK Mission Control (to inspect synchronization issue in JavaVM)
According to Mission Control, the servlet has a synchronization issue. It causes so many synchronization events when two or more requests come concurrently. The synchronization events are fired in a class used to lookup a table. The lookup table is implemented with ConcurrentHashMap. So the synchronization is not intentional and looks unnecessary.
On the other hand, according to the Performance Monitor, the number of concurrent requests and the CPU usage % are almost linearly increase together. This is an unexpected result for me.
I had expected that the CPU usage will become constant because the requests will be processed one by one due to the synchronization. As a result of more research, I have found the Java VM had introduced the Adaptive Spinning on Java 6, and I had set a hypothesis that this (spinlock for synchronization in Java VM) is the reason why the CPU usage increased linearly.
QuestionThe class that causes the synchronization issue is used in so many places in our application. To reasoning and explanation for the change to the class (remove the synchronized block from the class), I have to confirm the hypothesis with the result of a performance test. To confirm the hypothesis, I want to disable the spinlock for synchronization in Java VM.
I have found the JRockit and OpenJ9 had the command-line option to change the behavior of the adaptive spinning. But I could not find the equivalent for OpenJDK. There were no options related to spinlock in the result of java -XX:+PrintFlagsFinal -version.
Is there any way to disable the spinlock for synchronization in OpenJDK Java VM?
...ANSWER
Answered 2021-May-05 at 19:40The question is actually an XY problem. I'll answer it with the caveat that the experiment might be useless or even misleading.
The hypothesis that disabled spinning will decrease CPU usage is not necessary correct. Without spinning, a contended lock ends up in calling into OS kernel to park/unpark threads. A system call with a context switch is expensive, so, depending on the number of threads and the length of the critical section, this may actually increase CPU usage.
The options to disable spinning on intrinsic locks in OpenJDK 11 are:
QUESTION
I have a C shared library that is used from a Java application via JNI. I need to store some expensive-to-calculate data which will be valid for the lifespan of a JavaVM. I would like to store this in a static variable in C, so that it gets calculated exactly once.
Of course, this will fail if it is possible for my library to be used from multiple JavaVMs in the same process. My static values would only be valid in the first JavaVM. If my library is being loaded from Java via System.loadLibrary in a static block on a class, is it ever possible for said library to be used across multiple JavaVMs without having to completely unload my C shared library?
ANSWER
Answered 2021-Mar-19 at 16:48Yes. Most popular JVM implementations, in particular, HotSpot JVM and its derivatives, allow only one Java Virtual Machine per process.
In fact, an implementation allowing multiple VMs in one process, will not be compliant with the JNI specification, as the documentation to JNI_CreateJavaVM and JNI_GetCreatedJavaVMs explicitly says that
Creation of multiple VMs in a single process is not supported.
QUESTION
I want to convert an exception stacktrace to a string in C. I have this code:
(main.c)
...ANSWER
Answered 2021-Jan-04 at 17:48With this code, there were two issues:
Issue one:
QUESTION
In the following environment:
- Mac OS: Big Sur
- R: version 4.0.3
- Java: java version "1.8.0_271"
I am trying to run:
...ANSWER
Answered 2020-Dec-14 at 22:01JRI is currently not supported on Big Sur, because Apple has removed the last traces of Java support - here the JavaVM framework, so you have two options:
use
--disable-jriwhen installing rJava from sources (e.g. viainstall.packages("rJava", configure.args="--disable-jri"))use rJava from CRAN (i.e., install the binary version of rJava - not source)
The issue tracking this is #248
QUESTION
I have the following problem with a build stage of the Flutter app in Xcode. Trying to run a project inside a Android Studio I have faced some problems with a running project for iOS. As I see my project is builded in Xcode correctly and fully. But in a deployment fase on a iOS simulator the error happens due to some script(**Command PhaseScriptExecution **).
...ANSWER
Answered 2020-Nov-24 at 08:13please upgrade your flutter_svg to flutter_svg: ^0.18.0.
QUESTION
I have built docker image and while that I got the Error: no space left on device. This comes in the step where docker copies the oracle databse files. In my docker file it is this step:
...ANSWER
Answered 2020-Nov-13 at 11:15Question1: why does it stop even when I still have 9GB avilable on that partition?
You didn't when the error occurred. The error resulted in docker deleting the partial filesystem layer it had created. Note with overlay filesystems, a recursive chmod will copy every file in that directory tree, doubling the used disk space.
Note that you should also be watching for inode exhaustion when you get this write (df -i).
Question2: It seems that docker doesnt take space from the other partitions. On dev/sdc for example I have 718GB available. How to tell docker to take space from there?
Docker stores data in /var/lib/docker. I'd recommend making that it's own partition, or relocating it using a symlink rather than trying to change the location docker looks. There are lots of tools out there that assume this directory name.
Question3: It seems that docker write files into this folder /data/home/oracle/database/... But I go to that folder with winscp I can find only the directory /data. Is the folder /data/home/oracle/database/ in container somehow or its really in linux file system?
Docker uses namespaces, and one of those namespaces in the filesystem. The root directory in a docker container is not the root directory on the host, otherwise you'd have no isolation. This is typically implemented as an overlay filesystem under the docker directory, and each step of the Dockerfile may create a new filesystem layer used by overlay.
QUESTION
I decided using JVMTI to register all exceptions occured in JVM and build Histogram:
ClassName_method_ExceptionName:count
Agent attached like this:
taskset -c 10,12 java -agentpath:./jni-agent.so ${JVM_OPTION} -cp module.jar org.springframework.boot.loader.PropertiesLauncher &
I using this code for JNI agent:
...ANSWER
Answered 2020-Oct-22 at 00:52The crash reason is simple: your code is not thread safe.
Exception callback is invoked on the same thread that throws an exception. If multiple threads throw an exception concurrently, the callback is also invoked concurrently. std::map is not thread safe: concurrent access may cause a crash inside libstdc++.
The reason of slowness is more interesting.
How to analyze performance issues related to interaction between JVM and native? With async-profiler, of course. When profiling application startup, it's convenient to start profiler as an agent.
QUESTION
Does anyone know what the * following a filename in macOS terminal means?
All the file names in the folder:
/System/Library/Frameworks/JavaVM.framework/Versions/Current/Commands
have a * trailing them and I'm not sure why.
For example:
...ANSWER
Answered 2020-Sep-28 at 01:30As for the executable-looking emulator that you can't actually execute, this can happen when the dynamic loader requested by emulator doesn't exist. You can check what kind of file emulator is with the command file emulator, and check what dynamic loader and libraries it needs with ldd emulator (any line showing “not found” is something you need to install). Given the name of the directory and the size of the file, emulator is probably a Linux x86 binary. I suspect you have an amd64 system. If so, you need to install a runtime environment for 32-bit applications; on Ubuntu, you need the ia32-libs package (and perhaps also ia32-libs-gtk). You could also get this error message for a script whose interpreter as indicated in the #! line doesn't exist.
same question here.
QUESTION
class SmartAttachCurrentThread
{
public:
SmartAttachCurrentThread(JavaVM *jvm, JNIEnv *env) : jvm(jvm), env(env)
{
//TODO: throw if jvm null?
jvm->AttachCurrentThread(&env, NULL);
}
~SmartAttachCurrentThread()
{
jvm->DetachCurrentThread();
}
private:
JNIEnv *env;
JavaVM *jvm;
};
ANSWER
Answered 2020-Sep-22 at 17:41Your class constructor is taking the JNIEnv* parameter by value, that is why the env variable outside of the class is not being updated. You need to pass it by reference instead, eg:
QUESTION
How to async call Java method from std::thread ?
Let's assuming this is a IM bot sdk, Because it's logic basicly a IM bot sdk.
The most importtant is: How to async call java method and callback native.
There is logic flow at the bottom, Maybe helpful.
For example:
Receive message A "backup", Then call the java plugin with MsgA, The plugin porcess this event need 10second, And call 5 time native method for what ever it need.
Mean while, Receive message B "echo", That only take 10ms to process, And send an message by invoke native method.
So, MsgB recived after MsgA, But finish befor MsgA.
If using pure C C++ java or what ever, That will be so easy to achive. But here I found a headache problem: JNI thread Attach.
※ First question: Wired JNI attach
I have read doc find answer, None of them working and my condition different with everyone
I'm using Zulu JDK8 (zulu8.48.0.53-ca-fx-jdk8.0.265-win_x64) and MinGW64 C++, For demo:
...ANSWER
Answered 2020-Aug-21 at 06:55Looks like the your problems are not in usage of JVM but in C++ code. Looking at this piece of code:
Community Discussions, Code Snippets contain sources that include Stack Exchange Network
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No vulnerabilities reported
Install javavm
You can use javavm like any standard Java library. Please include the the jar files in your classpath. You can also use any IDE and you can run and debug the javavm component as you would do with any other Java program. Best practice is to use a build tool that supports dependency management such as Maven or Gradle. For Maven installation, please refer maven.apache.org. For Gradle installation, please refer gradle.org .
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