Likewise the -XX:SoftRefLRUPolicyMSPerMB flag is not guaranteed to be present in any given release. This behavior is not part of the VM specification, however, and is subject to change in future releases. The behavior described above is true for 1.3.1 through Java SE 6 versions of the Java HotSpot VMs.
On the other hand, the Client VM will have a greater tendency to flush soft references rather than grow the heap. This means that the general tendency is for the Server VM to grow the heap rather than flush soft references, and -Xmx therefore has a significant effect on when soft references are garbage collected.
#DO I NEED JAVA 8 64 BIT OR 32 FREE#
The Java Hotspot Client VM uses the current heap size to calculate the free space. The Java HotSpot Server VM uses the maximum possible heap size (as set with the -Xmx option) to calculate free space remaining. For example, to change the value from one second to 2.5 seconds, use this flag: This value can be adjusted using the -XX:SoftRefLRUPolicyMSPerMB flag, which accepts integer values representing milliseconds. The default value is one second of lifetime per free megabyte in the heap. Starting with 1.3.1, softly reachable objects will remain alive for some amount of time after the last time they were referenced. See also Tuning Garbage Collection with the 5.0 Java Virtual Machine. This may have worked before exact garbage collection became popular, but this is just not a good idea for any modern Java Virtual Machines. Don't use object pools! Using object pools will fool the collector into thinking objects are live when they really aren't.
To work around this, some programs keep an "object pool", saving previously allocated objects in some freelist-like data structure and reusing them instead of allocating new ones. Many systems have less efficient memory management than in HotSpot.
#DO I NEED JAVA 8 64 BIT OR 32 FULL#
If you are worried about the number of garbage collections, but less worried about pause times, then increasing the heap should cause the number of full garbage collections to decrease, this is especially true if you increase the size of the eden space as well. Using the above as an example, you can do the following in 1.4 and later: In 1.4 and later, MaxNewSize has been effectively set to infinity, and NewRatio can be used instead to set the value of the new generation. NewRatio (the ratio between the young/old generations) has values of 2 on Sparc Server, 12 on client Intel, and 8 everywhere else, as you can quickly determine, this is superseded by MaxNewSize's defaults (rendering NewRatio ineffective for even moderately sized heaps). For 1.3, MaxNewSize is set to 32mb on Sparc, 2.5mb on Intel based machines. Which will dedicate 1/3rd of the memory to eden. If you currently invoke with something like: For most programs, collecting eden is much faster than other generations because most objects die young. For some applications a very large eden helps, for others it will increase the times of minor collections. If your application requires more memory than you can adjust the size of the eden (young generation space) with -XX:NewSize=. A larger heap will cause garbage collection pauses to increase because there is more heap to scan. Next, you might try decreasing the amount of heap used. For most programs this results in shorter pauses, although throughput is usually worse. This uses the incremental garbage collection algorithm, which attempts to collect a fraction of the heap instead of the entire thing at once. There are several things to try in this arena.
0 kommentar(er)
