Common Java Performance Problems - Memory

Stop the world (STW) garbage collection

"The only remaining problem with the latest result above is the long Old generation (Full) GC pauses of about 8 seconds on average. These pauses have been made rare by proper generation tuning but when they occur they still are a nuisance to users because during their duration the JVM is not executing worker threads (stop-the-world GC). In our case, these 8 seconds are caused by an old and slow test server and could be up to a factor of 3 faster on modern hardware. On the other hand, today’s applications typically also use larger heaps than 1 GB and have larger amounts of live objects in the heap than in this example. Web applications nowadays work with heaps up to 64 GB and (at least temporarily) need half of that for their live objects. In such cases, 8 seconds is short for Old generation pauses. They can easily come close to one minute which is totally unacceptable for an interactive web application"

Tuning Garbage Collection for Mission-Critical Java Applications

Java memory leaks

"On the other hand, a non-growing or slow-growing memory leak is easily overlooked because it can seem so minor as to be unimportant. However, when such a leak is triggered by a single large object structure, the missing memory can pose a significant threat to the stability of the application. By using a modern heap-analyzer tool, we can track down this type of leak fairly quickly as is visualized in figure 2.25 (see the Analyzing Performance Impact section earlier in this chapter)."

Java memory leaks