We've run into a Java.lang.OutOfMemoryError: PermGen space error and looking at the tomcat JVM params, other than the -Xms and -Xmx params we also specify -XX:MaxPermSize=128m. After a bit of profiling I can see occasionally garbage collection happening on the PermGen space saving it from running full.
我们遇到了一个Java.lang。OutOfMemoryError: PermGen空间错误并查看tomcat JVM params，而不是-Xms和-Xmx params，我们还指定-XX:MaxPermSize=128m。在进行了一些分析之后，我可以看到在PermGen空间中偶尔会发生垃圾收集，从而节省了运行的时间。
My question is: other than increasing the -XX:MaxPermSize what would be the difference if I specify as well -XX:PermSize? I know the total memory then would be Xmx+maxPermSize but is there any other reason why -XX:PermSize should not be there when -XX:MaxPermSize is specified?
我的问题是:除了增加-XX:MaxPermSize之外，如果我指定了-XX:PermSize，那将会有什么不同?我知道总内存将是Xmx+maxPermSize，但是还有其他原因吗? xx:指定了maxPermSize时，PermSize不应该在那里?
Please do share if you have real-world experience dealing with these JVM parameters.
如果您有处理这些JVM参数的实际经验，请分享。
ps. The JVM is HotSpot 64bit Server VM build 16.2-b04
JVM是HotSpot 64位Server VM构建的16.2-b04。
3 个解决方案
#1
43
-XX:PermSize specifies the initial size that will be allocated during startup of the JVM. If necessary, the JVM will allocate up to -XX:MaxPermSize.
PermSize指定将在JVM启动时分配的初始大小。如果需要，JVM将分配到-XX:MaxPermSize。
#2
25
By playing with parameters as -XX:PermSize and -Xms you can tune the performance of - for example - the startup of your application. I haven't looked at it recently, but a few years back the default value of -Xms was something like 32MB (I think), if your application required a lot more than that it would trigger a number of cycles of fill memory - full garbage collect - increase memory etc until it had loaded everything it needed. This cycle can be detrimental for startup performance, so immediately assigning the number required could improve startup.
通过使用参数as - xx:PermSize和- xms，您可以对应用程序的启动进行优化。我最近都没看,但几年前xms的默认值是32 mb(我认为),如果您的应用程序需要大量,它将触发一个多周期的填充内存-完整的垃圾收集增加内存等之前加载所需的一切。这个循环可能不利于启动性能，因此立即分配所需的数量可以改善启动。
A similar cycle is applied to the permanent generation. So tuning these parameters can improve startup (amongst others).
同样的循环也适用于永久的世代。因此，调整这些参数可以改善启动(在其他方面)。
WARNING The JVM has a lot of optimization and intelligence when it comes to allocating memory, dividing eden space and older generations etc, so don't do things like making -Xms equal to -Xmx or -XX:PermSize equal to -XX:MaxPermSize as it will remove some of the optimizations the JVM can apply to its allocation strategies and therefor reduce your application performance instead of improving it.
警告JVM有很多优化和智能分配内存时,把伊甸园空间和老一辈人等,所以做事情不喜欢xms等于- xmx或- xx:PermSize等于- xx:MaxPermSize因为它会删除一些优化的JVM可以适用于它的分配策略,因此降低而不是提高应用程序性能。
As always: make non-trivial measurements to prove your changes actually improve performance overall (for example improving startup time could be disastrous for performance during use of the application)
和往常一样:用非平凡的度量来证明您的更改实际上提高了总体性能(例如，在使用应用程序时，改进启动时间可能会对性能造成灾难性的影响)
#3
7
If you're doing some performance tuning it's often recommended to set both -XX:PermSize and -XX:MaxPermSize to the same value to increase JVM efficiency.
如果您正在进行一些性能调优，通常建议将两个-XX:PermSize和-XX:MaxPermSize设置为相同的值，以提高JVM效率。
Here is some information:
这里有一些信息:
- Support for large page heap on x86 and amd64 platforms
- 支持x86和amd64平台上的大页面堆。
- Java Support for Large Memory Pages
- 对大内存页的Java支持。
- Setting the Permanent Generation Size
- 设置永久的生成大小。
You can also specify -XX:+CMSClassUnloadingEnabled to enable class unloading option if you are using CMS GC. It may help to decrease the probability of Java.lang.OutOfMemoryError: PermGen space
您还可以指定-XX:+CMSClassUnloadingEnabled来启用类卸载选项，如果您正在使用CMS GC。它可能有助于降低Java.lang的概率。OutOfMemoryError:PermGen空间
#1
43
-XX:PermSize specifies the initial size that will be allocated during startup of the JVM. If necessary, the JVM will allocate up to -XX:MaxPermSize.
PermSize指定将在JVM启动时分配的初始大小。如果需要，JVM将分配到-XX:MaxPermSize。
#2
25
By playing with parameters as -XX:PermSize and -Xms you can tune the performance of - for example - the startup of your application. I haven't looked at it recently, but a few years back the default value of -Xms was something like 32MB (I think), if your application required a lot more than that it would trigger a number of cycles of fill memory - full garbage collect - increase memory etc until it had loaded everything it needed. This cycle can be detrimental for startup performance, so immediately assigning the number required could improve startup.
通过使用参数as - xx:PermSize和- xms，您可以对应用程序的启动进行优化。我最近都没看,但几年前xms的默认值是32 mb(我认为),如果您的应用程序需要大量,它将触发一个多周期的填充内存-完整的垃圾收集增加内存等之前加载所需的一切。这个循环可能不利于启动性能，因此立即分配所需的数量可以改善启动。
A similar cycle is applied to the permanent generation. So tuning these parameters can improve startup (amongst others).
同样的循环也适用于永久的世代。因此，调整这些参数可以改善启动(在其他方面)。
WARNING The JVM has a lot of optimization and intelligence when it comes to allocating memory, dividing eden space and older generations etc, so don't do things like making -Xms equal to -Xmx or -XX:PermSize equal to -XX:MaxPermSize as it will remove some of the optimizations the JVM can apply to its allocation strategies and therefor reduce your application performance instead of improving it.
警告JVM有很多优化和智能分配内存时,把伊甸园空间和老一辈人等,所以做事情不喜欢xms等于- xmx或- xx:PermSize等于- xx:MaxPermSize因为它会删除一些优化的JVM可以适用于它的分配策略,因此降低而不是提高应用程序性能。
As always: make non-trivial measurements to prove your changes actually improve performance overall (for example improving startup time could be disastrous for performance during use of the application)
和往常一样:用非平凡的度量来证明您的更改实际上提高了总体性能(例如，在使用应用程序时，改进启动时间可能会对性能造成灾难性的影响)
#3
7
If you're doing some performance tuning it's often recommended to set both -XX:PermSize and -XX:MaxPermSize to the same value to increase JVM efficiency.
如果您正在进行一些性能调优，通常建议将两个-XX:PermSize和-XX:MaxPermSize设置为相同的值，以提高JVM效率。
Here is some information:
这里有一些信息:
- Support for large page heap on x86 and amd64 platforms
- 支持x86和amd64平台上的大页面堆。
- Java Support for Large Memory Pages
- 对大内存页的Java支持。
- Setting the Permanent Generation Size
- 设置永久的生成大小。
You can also specify -XX:+CMSClassUnloadingEnabled to enable class unloading option if you are using CMS GC. It may help to decrease the probability of Java.lang.OutOfMemoryError: PermGen space
您还可以指定-XX:+CMSClassUnloadingEnabled来启用类卸载选项，如果您正在使用CMS GC。它可能有助于降低Java.lang的概率。OutOfMemoryError:PermGen空间