Reprinted, please indicate the original source, thank you!
After 4 times of the twists and turns of the bounce, finally released the official version of Java 9! Today, looking at jdk9 everywhere, new features show that the idea of such a good program can be missed, ha ha, so the article was sent out.
At present, the norms of jdk9 and jvm9 have not yet come out, many details are not clear, basically through the official introduction, to see.
So you don’t worry
Go to the home page and download jdk9, and you’ll find out:
Don’t scare us like that. We don’t use it so quickly
After that, the download page was slightly different from the previous one, and there were no 32.
Java Platform, Standard Edition What ‘s New in Oracle JDK 9
Mainly based on the address: New in Oracle JDK 9. What ‘s New for JVM Tuning in JDK 9, other content can be interested to see, other I did not see.
These are the JVM tuning enhancements in JDK 9.
Improvement of G1Usability, Determinism, and Performance
It’s an internal improvement, a detailed description.
Deleting jdk8 deprecated garbage collector combinations
1. the following combination of DefNew + ParNew + SerialOld delete CMS Incremental CMS 2. foreground CMS GC foreground it delete the scene such as business thread request to allocate memory, but the memory is not enough, and may trigger a CMS GC, this process must be to memory assigned to the thread to continue to take the following, so the whole process must be STW CMS GC, so the whole process is to suspend the application, but in order to improve the efficiency of each stage, it is not will go, just take some stage thesaved stage mainly parallel stage, Precleaning, AbortablePreclean, Resizing did not experience these stages, including stage sweep are the same, but no matter what if go like foreground CMS GC, then the whole process of business threads are not available Efficiency will have a big impact. Reference: http://mp.weixin.qq.com/s? __biz=MzIzNjI1ODc2OA==& mid=403167528& idx=1& sn=915363f7daaf161c8cf8cd1953d377db& scene=19#wechat_redirect 3. JVM -Xincgc -XX:+CMSIncrementalMode -XX:+UseCMSCompactAtFullCollection to remove some of the parameters of -XX:+CMSFullGCsBeforeCompaction -XX:+UseCMSCollectionPassing 4. UseParNewGC The command line flag -XX:+UseParNewGC no longer has an effect. ParNew can only be used with CMS and CMS requires ParNew. Thus, the -XX:+UseParNewGC flag has been deprecated and will likely be removed in a future release. 5. use G1 as the default Risks and Assumptions The change collector is based on the assumption that limiting latency is often more important than maximizing throughput. If this assumption is incorrect Then this change might need to be reconsidered. G1 is seen as a robust and well-tested collector. It is not expected to have stability problems, but becoming the default collector will increase its visibility and may reveal previously-unknown issues. If a critical issue is found that can’t be addressed in the JDK 9 time frame, we will revert back to use Parallel GC as the default for the JDK The resource usage of 9 GA. G1 is different from Parallel. When resource usage overhead needs to be minimized a collector other than G1 should be used, and after this change the alternate collector will have to be specified explicitly.
simply means, similar to CMS, G1 is more concerned about the delay. If more attention is recommended PS throughput G1 is strong enough, maybe unknown, and if you can’t solve it, change the PS by default. 6. GC Garbage Collection unified log Reimplements (GC) logging using the unified JVM logging framework introduced in JEP logging is re-implemented in 158. GC a manner consistent with the current GC logging format however, some differences exist; between the new and old formats. 7. Deprecates the Concurrent Mark Sweep abandoned CMS (CMS) garbage collector. A warning message is issued when it is requested on the command line, using the -XX:+UseConcMarkSweepGC option. The Garbage-First (G1) garbage collector is intended to be a replacement for most uses of CMS. is a by the above can be seen from the CMS parameter to remove a lot, after some are abandoned, is to let the G1 instead of CMS, because CMS uses the mark is cleared, and G1 using a standard So G1 doesn’t need to do a defragmentation like CMS after several times of GC. The G1 garbage collector doesn’t have any special research, just knowing how to use marker sorting, and then there’s time to learn and share.
Today is probably so much, but also came out of many are not familiar with, but just a little more time to write, follow-up, follow-up Java every six months will release a version (pressure ah), I think JVM will become the perfect follow-up. I hope you will pay more attention to me, more support, praise, praise, thank you.
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