itouch generations

adjusted.After the class loader reads the class file, it is necessary to put the class, method, and constant variables into the heap memory to facilitate execution by the executor. In general, the memory allocation of objects is done on the heap.In the course of running a Java program, a large number of objects are generated, some of which are related to business information, such as session objects, threads, and socket connections in HTTP requests, which are directly linked to the business and

reaches the threshold, the 0 generation gc,0 GC is triggered to enter GEN1 after the surviving objects in Gen 0. If Gen 1 's memory reaches the threshold, the 1 generation gc,1 GC recycles the Gen 0 heap and Gen 1 heap, and the surviving objects enter Gen2. 2 Generation GC recycles the Gen 0 heap, Gen 1 heap, and Gen 2 heapGen 0 and Gen 1 are relatively small, these two generations are always kept at around 16M; the size of the Gen2 is determined by

and long-lived objects, the mark-compact collector was formed. though it is a bit more complex than copying collectors, the fundamental idea is the same. there is a definite separation between the active section of the memory and the free/unused section. however, unlike the copying collector, the mark-compact collector scans for all reachable objects and compacts them at the bottom of the heap, leaving the remaining memory free for consumption. the catch is that it doesn' t have to fully compac

StatisticsC:\Users\Administrator>jstat -gc 2060 S0C S1C S0U S1U EC EU OC OU MC MU CCSC CCSU YGC YGCT FGC FGCT GCT20480.0 20480.0 0.0 13115.3 163840.0 113334.2 614400.0 436045.7 63872.0 61266.5 0.0 0.0 149 3.440 8 0.295 3.735 1 2 3 1 2 3 S0C: The size of the first surviving area S1C: The size of the second surviving area S0U: The use

size CCSC: Compression class space size CCSU: Compression class space usage size YGC: number of young generations of garbage collection YGCT: waste collection time for young generation FGC: garbage collection times in the old age FGCT: time spent on garbage collection in the old age GCT: total time spent on garbage collection Heap Memory Statistics ngcmn: Cenozoic Minimum capacity NGCMX: maximum capacity of the Cenozoic NGC: Cu

module:Import Gcprint (Gc.get_threshold ())Return (700, 10, 10), followed by two 10 is the threshold associated with generational collection, which can be seen later. 700 is the threshold at which garbage collection starts. Can be reset by the Set_threshold () method in the GC.We can also start the garbage collection manually, that is, using Gc.collect ().Generational recyclingPython also uses the strategy of generational (generation) recycling. The basic assumption of this strategy is that the

garbage collection starts. Can be reset by the set_threshold () method in the GC.We can also start the garbage collection manually, that is, using gc.collect ().Generational RecyclingPython also uses the strategy of generational (generation) recycling. The basic assumption of this strategy is that the longer the surviving object, the less likely it is to become garbage in later programs. Our programs tend to produce a large number of objects, many objects quickly produce and disappear, but ther

of the Cenozoic, Laosheng generation and durable generations Gccause Used to view the statistics of garbage collection (this is the same as the-gcutil option), and if garbage collection occurs, it also shows the reason for the last and current garbage collection. Gcnew For viewing new generation garbage collection scenarios Gcnewcapacity For viewing the storage capacity of the Cenozoic

executes class bytecode. After the thread is created, the program counter (PC) and stack (stack) are generated, and the program counter holds the offset of the next instruction to be executed in the method, and the stack frames are stored in each stack frame, and each stack frame corresponds to each call of each method, and the stack frame is made up of the local variable area and the operand stack. Local variables are used to store local variables and parameters in the method, which are used t

. and transfer all surviving objects to one of the survivor areas. The Minor GC also checks for surviving objects and transfers them to another survivor area. In this way, there will always be an empty survivor area for a period of time. After several GC cycles, the surviving objects are transferred to the old generation memory space. This is usually done by setting an age threshold before the younger generation is eligible to ascend to the old age. Old Generation Older

mainstream virtual machines are extensible. If you do not have enough memory allocations or extensions after the garbage collection has been performed, you will throw a Outofmemoryerror:java heap space exception. There is much more to the heap area, which is described in detail in the next section, "Java Memory allocation mechanism." 5, methods area: In the Java Virtual Machine specification, the method area is treated as a logical part of the heap, but in fact, the method area is not a heap (n

mainstream virtual machines are extensible. If you do not have enough memory allocations or extensions after the garbage collection has been performed, you will throw a Outofmemoryerror:java heap space exception. There is much more to the heap area, which is described in detail in the next section, "Java Memory allocation mechanism." 5, methods area: In the Java Virtual Machine specification, the method area is treated as a logical part of the heap, but in fact, the method area is not a heap (n

extensible when implemented, and the current mainstream virtual machines are extensible. If you do not have enough memory allocations or extensions after the garbage collection has been performed, you will throw a Outofmemoryerror:java heap space exception. There is much more to the heap area, which is described in detail in the next section, "Java Memory allocation mechanism." 5, methods area: In the Java Virtual Machine specification, the method area is treated as a logical part of the heap,

(1) Parameter -XMS: initial Heap Size -XMX: Maximum heap Size This value can be set to be the same as-xmx to avoid the JVM reallocating memory after each garbage collection completes -XMN: Young Generation size whole heap size = young generation size + older generation size + persistent generation size. The permanent generation generally has a fixed size of 64m, so increasing the younger generation will decrease the size of the older generation. This value has a significant impact on system perf

and therefore have a long lifecycle. But there are some objects, mainly in the process of running the program generated temporary variables, these objects life cycle will be relatively short, such as: string objects, because of its invariant class characteristics, the system will produce a large number of these objects, some objects can be recycled even once. Just imagine that, without making a distinction between object survival time, each garbage collection is a collection of the entire heap

performance, and Sun officially recommends configuring the 3/8 of the entire heap.-xx:permsize=256m: Set heap Memory persistent generation initial value of 256M. (looks like an initialization parameter for an IDE such as Eclipse)-xx:maxnewsize=size: A newly generated object can occupy the maximum memory value.-XX:MAXPERMSIZE=512M: Set the maximum persistence generation to 512M.-xx:newratio=4: Sets the ratio of the young generation of heap memory (including Eden and two survivor areas) to the ol

1 usingSystem;2 3 namespacegctest4 {5 class Program6 {7 Static voidPrintstringstr) {Console.WriteLine (str);}8 Static voidMain (string[] args)9 {Ten varO1 =Newobj (); OnePrint"maximum algebra supported by the system:"+GC. maxgeneration); APrint"O1 on behalf of:"+GC. Getgeneration (O1));//The object was first created at the 0 generation - - //for all generations, the O1 is still alive, moving fro

memory can be organized after the replication, but there is a "Fragmentation" problem. Of course, the disadvantage of this algorithm is also obvious, that is, it requires two times of memory space. Mark-compact)This algorithm combines the advantages of "tag-clear" and "copy" algorithms. It is also divided into two phases. In the first phase, all referenced objects are marked from the root node. In the second stage, the whole heap is traversed to clear unlabeled objects and compress the survivi

. The shortest score is in The 0th generation, and the longest score is in the 2nd generation. The objects in the 2nd generation are usually relatively large. The generation level is related to the Framework version, which can be known by calling GC. maxgeneration. In general, GC collects the most recently allocated objects (0th generations) first, which is exactly the same as the "least recently used" Algorithm of the classic memory paging algorith

The CLR Garbage Collector uses the generation (generation) mechanism. Currently, it supports three generations: 0, 1, and 2: The newly constructed object added to the heap is called The 0th generation. After 0th generations of garbage collection, 0th generations of survivors were promoted to 1st generations. Af