One question about hotspot g1 heap adaptive resizing feature

[shaojun wang]

Hi Men Cao

I read one openjdk bug which discuss  G1 heap adaptive resizing feature, and I noticed that you mention one question like this:

[image.png]

and then you mentioned that you were convinced that the proposed approach does not suffer from this issue. This is because the proposed approach
does not rely on the total process CPU usage, and does not measure "GC CPU overhead", i.e., a ratio of GC CPU usage over total CPU usage.

[image.png]

my question is that even with GCTimeRatio(gc time / (gc time + app time)) , the problem will still exist if the application
fall into a very low cpu cost state. for example, gc_time = 30, app_time=40，GCTimeRatio is: 30/(30+40)= 0.42, the g1
heap size policy will try to extend heap size to scale down GCTimeRatio。But actually the application doesn't care about
its performance at all under the state，because there is basically no or merely request for the app. Do you have idea about
it?

https://github.com/openjdk/jdk/pull/24211
https://bugs.openjdk.org/browse/JDK-8359348

>From shaojun wang
ByteDance
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