Withdrawn: 8258414: OldObjectSample events too expensive

[Florian David]

On Fri, 19 Feb 2021 14:21:06 GMT, Florian David <fdavid at openjdk.org> wrote:

> The purpose of this change is to reduce the size of JFR recordings when the OldObjectSample event is enabled.
> 
> ## Problem
> 
> JFR recordings size blows up when the `OldObjectSample` is enabled. The memory allocation events are known to be very high traffic and will cause a lot of data, just the sheer number of events produced, and if stacktraces are added to this, the associated metadata can be huge as well. Sampled object are stored in a priority queue and their associated stack traces stored in `JFRStackTraceRepository`. When sample candidates are removed from the priority queue, their stacktraces remain in the repository, which will be later written at chunk rotation even if the sample has been removed.
> 
> ## Implementation
> 
> This PR adds a `JFRStackTraceRepository` dedicated to store stack traces for the `OldObjectSample` event. At chunk rotation, every sample stack trace is looked up in this repository and is serialized. Other stack traces are simply removed.
> 
> ## Benchmarks
> On an AWS c5.metal instance (96 cores, 192 Gib), running SPECjvm2008 with default profile.jfc configuration with OldObjectSample event enabled gives
> - a recording size 2.78Mb with the PR fix
> - a recording size 20.73Mb with the PR fix

This pull request has been closed without being integrated.

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PR: https://git.openjdk.java.net/jdk/pull/2644