RFR: JDK-8148736: Let the G1 heap transition log regions instead of bytes

kirk.pepperdine at gmail.com kirk.pepperdine at gmail.com
Tue Feb 2 06:38:58 UTC 2016


Hi Bengt,


>> So my understanding of the thread suggests that this decision is based on a very specialized condition created by this benchmark that wastes a lot of memory. Again, it is my opinion that occupancy are important and that relying on an estimate based on region size is simply far too course a measure for 1M regions and only gets worse as region size increases. That’s not accounting for the inaccuracy due to waste. I have a number of experimental analytics that will tolerate a fair amount of “noise” in the data when using K granularity. Using M granularity is and issue that this gives us even worse precision than that.
> 
> The estimation you get by multiplying with the region size is exactly as good or as bad as it was before when that multiplication was done in the code. So, I don't really understand your accuracy argument.

In this case I misunderstood the comments in the bug report. From what I understood is that count was accurate. If this is not the case it may explain some of the strange things I’ve been seeing in G1 logging. I will have to take a look at the impact of having to use trace to get accurate information.

Regards,
Kirk



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