What are the key performance metrics of a garbage collector?

Let’s review them in detail:

Garbage Collection Pause Times. You should measure Garbage collection pause times, as during GC pauses entire application freezes.
Object Creation/Reclamation Rate.
Garbage Collection Throughput.
Memory consumption by each generation.

What is long GC pauses?

Garbage collection (GC) is the process by which Java removes data that is no longer needed from memory. A garbage collection pause, also known as a stop-the-world event, happens when a region of memory is full and the JVM requires space to continue. During a pause all operations are suspended.

How do you measure garbage collection?

To determine the length of time in a garbage collection

Examine the % Time in GC memory performance counter.
Alternatively, you can determine the length of a garbage collection by using garbage collection ETW events, and analyze the information to determine the duration of garbage collection.

What are generations in garbage collector?

A generational garbage collector collects the short-lived objects more frequently than the longer lived ones. Short-lived objects are stored in the first generation, generation 0. The longer-lived objects are pushed into the higher generations, 1 or 2.

What is garbage collection in performance testing?

Garbage collection is the memory management process for objects in the heap. As objects are allocated to the heap, they run through a few collection phases – usually rather quickly as the majority of objects in the heap have short lifespans.

How does garbage collection affect performance?

An application that spends 1% of its execution time on garbage collection will loose more than 20% throughput on a 32-processor system. If we increase the GC time to 2%, the overall throughput will drop by another 20%. Such is the impact of suspending 32 executing threads simultaneously!

What is G1 humongous allocation?

Humongous allocations are allocations over 50% of the G1 region size (the region size is another statistic printed in the GC log at the end of each collection). If your app uses humongous allocations heavily it can lead to excessive memory fragmentation and OutOfMemoryError exceptions.

How do I reduce GC pauses?

If your application’s object creation rate is very high, then to keep up with it, the garbage collection rate will also be very high. A high garbage collection rate will increase the GC pause time as well. Thus, optimizing the application to create fewer objects is THE EFFECTIVE strategy to reduce long GC pauses.

How many types of generations are there in a garbage collector?

three generations
Garbage collection primarily occurs with the reclamation of short-lived objects. To optimize the performance of the garbage collector, the managed heap is divided into three generations, 0, 1, and 2, so it can handle long-lived and short-lived objects separately.

How does garbage collection improve program performance?

Because unreferenced objects are automatically removed from the heap memory, GC makes Java memory-efficient. Garbage collection frees the programmer from manually dealing with memory deallocation. By then the memory may have been reassigned to another use with unpredictable results.

Does garbage collection affect performance Java?

The most common performance problem associated with Java™ relates to the garbage collection mechanism. If the size of the Java heap is too large, the heap must reside outside main memory. This causes increased paging activity, which affects Java performance.

What are the key performance metrics of a garbage collector?