TLAB of JVM

One 、 Put forward ：

The heap is a thread shared area , Any thread can access the shared data in the heap , Because of the creation of object instances jvm Very often , Therefore, it is unsafe for threads to divide the memory space in the heap in the concurrent environment , In order to avoid multiple threads operating on the same address , You need to use mechanisms like locking , This affects the distribution speed .

Two 、 What is? TLAB;

  3、 ... and 、 The illustration ：

Four 、TLAB Detailed instructions ：

a、 Although not all object instances can be in TLAB Successfully allocated memory in , but JVM It's going to be TLAB As the first choice for memory allocation

b. In the program , Developers can use options ：“-XX:UserTLAB” Set whether to turn on TLAB Space

c. By default ,TLAB The memory of the space is very small , Only the whole Eden Spatial 1%, Of course, we can choose “-XX：TLABWasteTarget'Percent” Set up TLAB Space occupied Eden Percentage size of space .

d、 Once the object is in TLAB When space allocation fails ,JVM Will try to ensure the atomicity of the data by using the locking mechanism , So directly in Eden Allocate memory in space .

Four 、 Graphic process of object assignment ：