RFR: 8319548: Unexpected internal name for Filler array klass causes error in VisualVM

[jjscl8888]

On Fri, 3 May 2024 12:50:45 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

> (because the bot does not seem to forward the answer from the mailing list within a few hours; fwiw, it has been pure luck that I stumbled across that question within github):
> 
> On 30.04.24 03:38, jjscl8888 wrote:
> 
> > Thank you for your clarification. if the instance in question had no
> > traffic but you observed a sudden increase in the old generation size
> > at 2:35 in the graph, and subsequent garbage collections (GCs) did not
> > reduce the size of the old generation back to its original value
> 
> Collectors are fairly reluctant to give back memory to the OS.
> 
> For G1 in particular, there are the options `MinHeapFreeRatio` and `MaxHeapFreeRatio` which to some degree steer commit and uncommit.
> 
> * `MinHeapFreeRatio` is "The minimum percentage of heap free after GC to avoid expansion", i.e. minimum amount of memory should be kept free. Default is 40%, i.e. expands if less than that amount of memory is free.
> * `MaxHeapFreeRatio` is "The maximum percentage of heap free after GC to avoid shrinking", i.e. maximum amount of memory that should be kept free. Default is 70%; i.e. only shrinks the heap if more than 70% of memory is free.
> 
> Not sure the latter condition is met here to shrink, and without logs (`-Xlog:gc+ergo+heap=debug`) this is just a guess. Also, this kind of heap resizing (including shrinking) only occurs in the Remark pause.
> 
> So to decrease the heap more aggressively, it might work to decrease `MaxHeapFreeRatio` (and probably `MinHeapFreeRatio` too because for such large heaps the default values are maybe not optimal).
> 
> Hth, Thomas

Thank you for your previous question. I have another inquiry regarding compiling the JDK source code. I've noticed that when I compile the JDK without selecting specific configure parameters, the resulting JDK size differs from the official version available on the website. I'm curious to know which configuration parameters were used for the official LTS (Long-Term Support) version of the JDK.

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PR Comment: https://git.openjdk.org/jdk/pull/17155#issuecomment-2099609444