Request for sponsor - JDK-8031538

[Thomas Schatzl]

Hi Staffan,

On Mon, 2015-03-02 at 15:42 -0800, Staffan Friberg wrote:
> Found this old thread lying around.
> 
> How about the following patch?
> 
> Checking the calculate_young_list_desired_min_length which simply just 
> adds the base_min_length I think changing the base_min_length to contain 
> more than survivors might increase the nursery size unexpectedly. This 
> will keep the calculation the same, while still making sure we can't set 
> the young size below what the it currently is.
> 
> @@ -538,13 +538,13 @@
>     // This is how many young regions we already have (currently: the 
> survivors).
>     uint base_min_length = recorded_survivor_regions();
>     // This is the absolute minimum young length, which ensures that we
> -  // can allocate one eden region in the worst-case.
> -  uint absolute_min_length = base_min_length + 1;
> +  // will at least have one eden region available in the young list.
> +  // If we shrink the young list target it won't shrink below the 
> current size.
> +  uint eden_length = _g1->young_list()->length() - 
> recorded_survivor_regions();
> +  uint absolute_min_length = base_min_length + (eden_length == 0) ? 1 : 
> eden_length;
>     uint desired_min_length =
> calculate_young_list_desired_min_length(base_min_length);
> -  if (desired_min_length < absolute_min_length) {
> -    desired_min_length = absolute_min_length;
> -  }
> +  desired_min_length = MAX2(desired_min_length, absolute_min_length);
> 
>     // Calculate the absolute and desired max bounds.

  looks good; I applied some minor refactoring (the eden length
calculation moved to the YoungList class). If you are good with these
changes, I can sponsor it.

Webrev: http://cr.openjdk.java.net/~tschatzl/8031538/webrev/

Thanks,
  Thomas