garbage-collection

问题 Running with JVM: java version "1.7.0_79" Java(TM) SE Runtime Environment (build 1.7.0_79-b15) Java HotSpot(TM) 64-Bit Server VM (build 24.79-b02, mixed mode) OS: CentOS release 6.4 (Final) Jvm Options: -Xmx4g -Xms4g -XX:MaxPermSize=4g -XX:+HeapDumpOnOutOfMemoryError -XX:+PrintClassHistogram -XX:+CMSClassUnloadingEnabled -verbose:gc -XX:+UseG1GC -XX:MaxGCPauseMillis=200 -XX:+DisableExplicitGC Running in an OSGI environment, Aerospike DB, NETTY (NIO) for networking. Ran a weekend longevity

问题 Running with JVM: java version "1.7.0_79" Java(TM) SE Runtime Environment (build 1.7.0_79-b15) Java HotSpot(TM) 64-Bit Server VM (build 24.79-b02, mixed mode) OS: CentOS release 6.4 (Final) Jvm Options: -Xmx4g -Xms4g -XX:MaxPermSize=4g -XX:+HeapDumpOnOutOfMemoryError -XX:+PrintClassHistogram -XX:+CMSClassUnloadingEnabled -verbose:gc -XX:+UseG1GC -XX:MaxGCPauseMillis=200 -XX:+DisableExplicitGC Running in an OSGI environment, Aerospike DB, NETTY (NIO) for networking. Ran a weekend longevity

问题 Running with JVM: java version "1.7.0_79" Java(TM) SE Runtime Environment (build 1.7.0_79-b15) Java HotSpot(TM) 64-Bit Server VM (build 24.79-b02, mixed mode) OS: CentOS release 6.4 (Final) Jvm Options: -Xmx4g -Xms4g -XX:MaxPermSize=4g -XX:+HeapDumpOnOutOfMemoryError -XX:+PrintClassHistogram -XX:+CMSClassUnloadingEnabled -verbose:gc -XX:+UseG1GC -XX:MaxGCPauseMillis=200 -XX:+DisableExplicitGC Running in an OSGI environment, Aerospike DB, NETTY (NIO) for networking. Ran a weekend longevity

问题 What guarantees are the for the garbage collector? From my research I have managed to find: If there is still a reference to the memory it will not be garbage collected If there is no reference: When it is GC is non deterministic When the GC kicks in the finalizer will be run before memory is released. There is no guarantee about the order of Finalizers (so do not assume parent will be run before child). But what I really want to know is: Is there a guarantee that all memory will eventually

问题 What guarantees are the for the garbage collector? From my research I have managed to find: If there is still a reference to the memory it will not be garbage collected If there is no reference: When it is GC is non deterministic When the GC kicks in the finalizer will be run before memory is released. There is no guarantee about the order of Finalizers (so do not assume parent will be run before child). But what I really want to know is: Is there a guarantee that all memory will eventually

问题 I have the following code to test out the memory use for node vm: setInterval(()=>console.log(process.memoryUsage()),1000); ( ()=> { const MAXTIMES = 10000000; let a = ( ()=> { let res = ""; for(let i=0; i<MAXTIMES; i++){ res = res + "X"; } return res; })(); })(); //Uncomment this to give enough time for GC and check top command. //Not needed with setInterval in the beginning //setTimeout(()=>{}, 10000); top command shows vm uses ~420M memory. When I change the max value of i to 100000000

问题 I heard an associate say: JVM garbage collection times increase exponentially with JVM size. This is because the tree of references is a function of the amount of the amount of objects to allocate - and gets exponentially harder to traverse the tree as the number of objects get bigger. This sounded right. I heard another associate say: JVM garbage collection on the same machine is linear. Given an 8GB JVM split in two 4G JVMs on the same machine (via microservices) will have the same garbage

问题 I always wondered how clean is such approach - to remove an event listener from within that very listener. UPDATE: Internally I keep a hash of objects and listeners, so I potentially can remove event listener from any place. I'm just concerned of removing it from within itself. Will such action do a job actually? UPDATE I'm asking about addEventListener, removeEventListener stuff. 回答1: You can pass the once option to have a listener act only once, then remove itself. Docs: https://developer

问题 I always wondered how clean is such approach - to remove an event listener from within that very listener. UPDATE: Internally I keep a hash of objects and listeners, so I potentially can remove event listener from any place. I'm just concerned of removing it from within itself. Will such action do a job actually? UPDATE I'm asking about addEventListener, removeEventListener stuff. 回答1: You can pass the once option to have a listener act only once, then remove itself. Docs: https://developer

问题 Given an object obj is there a guarantee that uintptr(unsafe.Pointer(&obj)) will always evaluate to the same value regardless of when it is called? Of course, Go guarantees that if you take two pointers to the same object, they will always compare equal. It might be possible though that an implementation moves an object in memory and transparently updates all pointers to it. This is interesting if you consider garbage collection strategies like Mark-and-Compact. Would an implementor be