On The Costs of Hidden Logging

Mon, 11 Oct 2021 08:05:33 +0000

A while ago I received a customer escalation ticket regarding performance degradation when using Datadog Continuous Profiler for Java . The degradation was observable as an increased CPU usage as well as unexpected latency.

The Beginning: Unusual Customer Escalation

To bootstrap the troubleshooting, I usually try to isolate the area which might be causing the regression.

The profiler is packaged as a Java agent and for ease of use it is bundled together with the Datadog Java tracer agent. The profiler itself uses JDK Flight Recorder (JFR) under the hood.

Improved JFR Allocation Profiling in JDK 16

Wed, 17 Feb 2021 09:46:33 +0000

JFR (JDK Flight Recorder) has been providing the support for on-the fly allocation profiling for a while with the help of ObjectAllocationInNewTLAB and ObjectAllocationOutsideTLAB events.

Short excursion - what is TLAB?

TLAB stands for Thread Local Allocation Buffer and it is a region inside Eden, which is exclusively assigned to a thread. Each thread has its own TLAB. Thanks to that, as long as objects are allocated in TLABs, there is no need for any type of synchronization. Allocation inside TLAB is a simple pointer bump (that’s why it’s sometimes called pointer bump allocation).

Jaroslav Bachorik on foojay.io - Friends of OpenJDK

On The Costs of Hidden Logging

The Beginning: Unusual Customer Escalation

Improved JFR Allocation Profiling in JDK 16