More compacting GC

Jon Coppeard recently extended SpiderMonkey’s compacting GC abilities. Previously, the GC could only compact GC arena containing JavaScript objects. Now it can also compact arenas containing shapes (a data structure used within SpiderMonkey which isn’t visible to user code) and strings, which are two of the largest users of memory in the GC heap after objects.

These improvements should result in savings of multiple MiBs in most workloads, and they are on track to ship in Firefox 48, which will be released in early August. Great work, Jon!

2 Responses to More compacting GC

  1. Awesome!
    Would love to see a numbers/graph comparison at some point with the same sites.

  2. Daniel Neely

    Were these improvements lost in the noise on AWSY? Nothing is jumping out at the times the results were posted to the bugs.