RFR(S): 8209162: Page size selection does not always select optimal page size

[Stefan Johansson]

Hi Ivan,

I'm not very familiar with this code, but one observation. This is a bit 
similar to what I looked at recently for G1. There the region size was 
different for a given heap size depending on if Xms was set or not. Here 
we can run into a situation where the page size differ depending on Xms, 
and this also feels a bit strange. Would there be a problem to simplify 
this to a single line and always just care about min:
const size_t page_sz = os::page_size_for_region_aligned(MinHeapSize, 4);

I'm trying to understand when this would be a problem, but can't think 
of anything straight away.

Cheers,
Stefan

On 2020-04-18 12:04, Ivan Walulya wrote:
> 
> 
>> On 17 Apr 2020, at 12:40, Bernd Eckenfels <ecki at zusammenkunft.net> wrote:
>>
>> It looks rather confusing to use the min_pages variable for two sizes, maybe better call it pages?
> 
> Thanks for pointing this out. Refactored, hope it is clearer now.
> https://cr.openjdk.java.net/~iwalulya/8209162/01/ <https://cr.openjdk.java.net/~iwalulya/8209162/01/>
> 
>>
>> BTW i am not sure why the minimum number of pages does not apply to the static side heap case. Isn't there requirement fūr the 4 generations present in all cases? Maybe the comment can describe this more cleanly.
> 
> const size_t page_sz = MIN2(max_page_sz, min_page_sz); would handle this case.
>   I hope the refactored code is less confusing.
> 
>>
>>
>> --
>> http://bernd.eckenfels.net
>