I’m no expert here, but here’s something: Box 1, no NUMA: ~$ dmesg | grep -i numa [ 0.000000] No NUMA configuration found Box 2, some NUMA: ~$ dmesg | grep -i numa [ 0.000000] NUMA: Initialized distance table, cnt=8 [ 0.000000] NUMA: Node 4 [0,80000000) + [100000000,280000000) -> [0,280000000)
Terracotta DSO works by manipulating the byte code of your classes (and the JDK’s classes etc). The instructions on how and when to do this are part of the Terracotta configuration file. The bytecode modification looks for certain byte codes such as a field read or write or a monitor enter or exit. Whenever those … Read more
The short answer To find out how large an object is, I would use a profiler. In YourKit, for example, you can search for the object and then get it to calculate its deep size. This will give a you a fair idea of how much memory would be used if the object were stand … Read more
THERE ARE ERRORS BELOW DEPENDING ON THE JVM/JRE THAT YOU USE. IT IS BETTER TO NOT WORRY ABOUT THINGS LIKE THIS ANYWAYS. SEE COMMENTS SECTION FOR ANY CORRECTIONS/CONCERNS. First, this question really asks about this addressed here: Is String Literal Pool a collection of references to the String Object, Or a collection of Objects So, … Read more
In Sun’s JVM, last I knew, the entire heap must be allocated in a contiguous address space. I imagine that for large heap values, it’s pretty hard to add to your address space after startup while ensuring it stays contiguous. You probably need to get it at startup, or not at all. Thus, it is … Read more
Take a look at the HotSpot VM Options: -XX:+UseParallelGC = Use parallel garbage collection for scavenges. (Introduced in 1.4.1). -XX:+UseParallelOldGC = Use parallel garbage collection for the full collections. Enabling this option automatically sets -XX:+UseParallelGC. (Introduced in 5.0 update 6.) where Scavenges = Young generation GC.
The initial heap size is the minimum heap size. It won’t get smaller than the initial heap size. From Tuning Garbage Collection with the 5.0 Java[tm] Virtual Machine: By default, the virtual machine grows or shrinks the heap at each collection to try to keep the proportion of free space to live objects at each … Read more
The field y is not declared by class Checks. Reading static fields doesn’t trigger initialization of the referenced class (Checks), unless that class is the one in which the field is declared (see JLS quote below). In this example, even if y is accessed through Checks, that will only trigger the initialization of Par because … Read more
To check it for particular release: java -XX:-AggressiveOpts -XX:+UnlockDiagnosticVMOptions -XX:+PrintFlagsFinal -version > no_agg java -XX:+AggressiveOpts -XX:+UnlockDiagnosticVMOptions -XX:+PrintFlagsFinal -version > agg And then make diff (diff -U0 no_agg agg). For example, jdk 1.7.0_51: – bool AggressiveOpts := false {product} + bool AggressiveOpts := true {product} – intx AutoBoxCacheMax = 128 {C2 product} + intx AutoBoxCacheMax = … Read more
In Java version 8u92 the VM arguments -XX:+ExitOnOutOfMemoryError -XX:+CrashOnOutOfMemoryError were added, see the release notes. ExitOnOutOfMemoryError When you enable this option, the JVM exits on the first occurrence of an out-of-memory error. It can be used if you prefer restarting an instance of the JVM rather than handling out of memory errors. CrashOnOutOfMemoryError If this … Read more