how to monitor java memory usage

Import java. Io. file;Import java. Io. inputstreamreader;Import java. Io. linenumberreader;Import java. Lang. Management. managementfactory;Import java. util. arraylist;Import java. util. List; Import com. Sun. Management. operati

Recently, a project was designed to obtain information about the cpu usage and so on. At first, I thought it was necessary to use a dynamic link library, but later I found that I could do the following without calling jni, this saves a lot of time for reading new technologies... In Java, you can obtain information such as the total physical memory, the remaining

multiples of 8, and the object occupies a multiple of the total space (object header + declaration variable) less than 8, and is automatically padded. And, these filled spaces, we can call it "filler." Let's take a look at the specific examples: An empty object (without declaring any variables) takes up 8 bytes--> object Header occupies 8 bytes A class that only declares a Boolean variable, occupies a bytes-to-Object header (8 bytes) + Boolean (1 bytes) + filler (7 bytes) Class

Copy from:http://www.javamex.com/tutorials/memory/instrumentation.shtmlInstrumentation:querying the memory usage of a Java objectThe most reliable-but isn't necessarily the easiest-way to estimate the usage of a Java object are to

One of the best known advantages of Java technology is that, unlike other languages such as C programmers, Java programmers do not have to be responsible for daunting memory allocations and releases. The Java runtime can manage these tasks for you. Each instantiated object automatically allocates

, exclude 2. Use the Finalize function as little as possible. It will increase the workload of the GC.3. If you need to use a frequently used picture, you can use the Soft app type. It keeps the picture in memory as much as possible.4. Note the collection data types, including arrays, trees, graphs, linked lists, and other data structures, which are more complex for GC to recycle.5. Try to avoid creating and initializing a large number of objects in t

Java command simple view JVM memory usage1. JPS Virtual machine process Status ToolSyntax jsp [option] [HostID]OptionsRole-QShow Only Lvmid-MPass in Main method parameter when output virtual machine is enabled-LOutput main class full Name-VOutput JVM ParametersAttention:If the JPS command cannot output vmid data (jdk1.6.0.23/24 bug) in a Linux environment, the catalina.sh file needs to be modifiedIf [-Z "$C

Database Data occupies memory in Java. Conclusion: 1. database records are stored in JAVA. It takes about 4 times of memory space to use an object (which is a common ORM processing method), and 10 times of space to use HashMap to store KV data. 2. if your main data is text, you can estimate the space by two times. The

I have made some optimizations on the memory usage of the program recently, and have achieved good results. I have summarized some experiences. I believe it will be helpful for you to write high-quality programs. The following discussion is not applicable to 64-bit systems for 32-bit systems. You often write a program, test it, and have no function problems. When you check that the

Mention of the memory usage when the Java process is running is a confusing place for many beginners, which is how the JVM applies the memory to the operating system when we run the compiled. class file. You can use the JDK's own run-time system parameters to describe the three methods in class runtime to view Runtime.

(411.06592559814453 MB)20.152302906758376% usedPS Perm GenerationCapacity = 85983232 (82.0 MB)Used = 60770232 (57.95500946044922 MB)Free = 25213000 (24.04499053955078 MB)70.67684080542588% used and then use ps to look at it:[Lex @ chou ~] $ Ps-p 837-o vsz, rssVSZ RSS7794992 3047320 I will not elaborate on the several generation online materials here. Here, we can calculate the sum and we can see that the former has allocated a total of 64 4 MB of memory