[Rare case] G1 mixed GC didn't reclaim garbages in 8u

Thomas Schatzl thomas.schatzl at oracle.com
Fri Feb 7 11:09:46 UTC 2020


On 07.02.20 06:39, Liang Mao wrote:
> Hi All,
> I saw a rare case that G1 almost clear nothing in mixed GC but later full GC
> reclaimed 70% of the heap. The version is 8u and is there any bug or is it
> an extreme case of floating garbage because of SATB?

   hard to say. It may just be the application keeping data alive as you 
indicate. I am not aware of a particular jdk8 bug that keeps objects 
alive unnecessarily.

G1LogLevel=finest would give answer to why the mixed phase stopped 
early. It would not give insight about what exactly kept the data alive 


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