JDK-8200723 : Suppress rs_length and predicted_cards sampling during mixed gcs
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: gc
  • Affected Version: 11
  • Priority: P4
  • Status: Resolved
  • Resolution: Fixed
  • Submitted: 2018-04-04
  • Updated: 2018-06-21
  • Resolved: 2018-04-18
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JDK 11
11 b11Fixed
Related Reports
Relates :  
JDK-8035557 - Pause time predictions off for mixed collections due to wrong rs_length estimation
Description
Related to JDK-8035557, one way to temporarily fix the issue with the wrong predictions of rs length and card prediction is to suppress sampling of these metrics during mixed gc.

Since mixed gc does not use these, sampling during mixed gc only inflates these predictions for the young gc following mixed gcs.

The disadvantage is that the prediction for this first young gc after the mixed gc might be off due to many leftover cards from the mixed phase.
Comments
This change somewhat decreases the issues shown in JDK-8035557, however it would be still interesting to fix that properly.
04-04-2018