RFR(xs): 8221517: G1: Reserved page size for heap can be wrong

[Thomas Schatzl]

Hi Sangheon,

On Thu, 2019-03-28 at 20:47 -0700, sangheon.kim at oracle.com wrote:
> Hi all,
> 
> Can I have some reviews for the patch which fixes wrong G1 heap page 
> size issue?
> 
> The page size which is used to decide G1 heap mapper comes from 
> preferred page size or heap alignment. However, if it came from heap 
> alignment, we have to limit to actual large page size if it is
> larger than large page size.

Thanks for catching this.

> 
> I added a new jtreg test to check this problem. It relies on the
> error message when printed if reserving memory with large page fails.
> Unfortunately, Solaris has a bug that the error message is printed
> even in success. To address this problem I filed 'JDK-8221526:
> Solaris: large page reservation failure message is printed even in
> success.' and the test is excluded on Solaris.

- g1CollectedHeap.cpp:1578: s/alginment/alignment ,
s/ResesrvedSpace/ReservedSpace

- Could you rewrite line 1581 with:

page_size = MIN2(rs.alignment(), os::large_page_size());

That would be a lot shorter and as understandable than the three extra
lines imho.

- TestLargePageUseForHeap.java:28: maybe add "... is allocated using
large pages of the appropriate size if available" to the @summary tag.

> CR: https://bugs.openjdk.java.net/browse/JDK-8221517
> webrev: http://cr.openjdk.java.net/~sangheki/8221517/webrev.0
> Testing: hs-tier1 ~ 5

Thanks,
  Thomas