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Poonam Parhar

Consulting Member of Technical Staff

Recent Posts by Poonam Parhar

Wednesday, February 28, 2018 Poonam Parhar

StackOverflowError and threads waiting for ReentrantReadWriteLock

If the terms 'Stuck Threads' or 'Hang' sound familiar and scary to you, please read on. We can sometimes come across situations where the Weblogic Server (WLS) reports some threads as being 'Stuck' or 'not making any progress', but the stack traces of those threads and others in...

Monday, December 11, 2017 Poonam Parhar

Can young generation size impact the application response times?

I was recently involved in a performance issue where the application's response times were decreasing over time, and I was tasked to determine if GC was playing any role in that. Well, as we all know that misconfiguration of the java heap space and its generations can lead to...

Tuesday, November 14, 2017 Poonam Parhar

Clarifying some confusion around Java Flight Recordings

In this blog, I am going to talk about two confusions around Java Flight Recordings that I have come across from multiple users/customers. Let's take a look at them one by one. Flight Recordings Interval A number of Java Flight Recorder users seem to have a confusion around the...

Wednesday, May 10, 2017 Poonam Parhar

How do I find what's getting promoted to my old generation?

This question comes up every now and then that how can I find what the minor/young collections are promoting to the old generation of my Java application. Recently, there was a case where the customer wanted to know the types of objects getting promoted to the old generation at...

Thursday, April 27, 2017 Poonam Parhar

HotSpot JVM throwing OOM even when there is memory available

I was recently asked a question that why my Java application runs out of Java Heap when there is still so much memory available to use? Here is the question in detail - I am running my application with -Xmx1600m but the logs show that it runs out of memory without fully using the...

Thursday, February 16, 2017 Poonam Parhar

WeakReferences and GC

I was recently working on a memory growth issue involving WeakReferences, and I came across this great blog post on how non-strong references can affect the heap usage and the garbage collection:https://plumbr.eu/blog/garbage-collection/weak-soft-and-phantom-references-impact-on-g...

Wednesday, November 2, 2016 Poonam Parhar

Hung JVM due to the threads stuck in pthread_cond_timedwait()

In this post, I am going to discuss a couple of scenarios where the Java process hangs are actually NOT because of a Java/JVM issue but happen due to the OS problems. Both the hangs being discussed here occur on the Linux operating system. Lets take a look at the first case where...

Thursday, October 27, 2016 Poonam Parhar

G1 and Flight Recorder's -XX:FlightRecorderOptions=stackdepth option

Recently there was a report from a customer that they observed performance degradation while using JFR with G1 when they used it along with -XX:FlightRecorderOptions=stackdepth=512, but didn't see any performance impact when using the same setting for the stackdepth with the...

Wednesday, September 28, 2016 Poonam Parhar

Crashes in ZIP_GetEntry

Recently, received quite a few reports of the application crashes from different customers and product groups with the stack trace looking like this: Stack: [0xb0c00000,0xb0c80000], sp=0xb0c7c890, free space=498kNative frames: (J=compiled Java code, j=interpreted, Vv=VM code,...