RFR: 8271195: Use largest available large page size smaller than LargePageSizeInBytes when available [v3]

[Swati Sharma]

On Fri, 25 Feb 2022 13:06:22 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

> XX:ReservedCodeCacheSize=<> -XX:InitialCodeCacheSize=<>

Hi @albertnetymk , @kstefanj ,

I have pushed the changes as suggested by @kstefanj, Initial version created was having explicit predicate  conditions for each test case and was in line to what is being proposed by you.  To accommodate your comments I have modified the test to include explicit -XX:ReservedCodeCacheSize and considering it while computing the required page count.

With this we should be able extend the existing test case to cover all the comments instead of re-instantiating initial test case version.

Looking forward to your feedback and approval.

Thanks,
Swati Sharma

PS:  Following are  the performance numbers for modified JMH benchmark over 2S 40C Ice lake Server (Intel(R) Xeon(R) Platinum 8380)

2M pages
Benchmark                           (ARRAYSIZE)  (NUM)   Mode  Cnt        Score         Error    Units
MicroLargePages.micro_HOP_DIST_4KB      2097152      1  thrpt   10  2047721.586 ± 1100027.488  ops/min
MicroLargePages.micro_HOP_DIST_4KB      2097152      2  thrpt   10   741954.577 ±  174530.486  ops/min
MicroLargePages.micro_HOP_DIST_4KB      2097152      4  thrpt   10   330249.555 ±   31666.913  ops/min

4K pages
Benchmark                           (ARRAYSIZE)  (NUM)   Mode  Cnt        Score        Error    Units
MicroLargePages.micro_HOP_DIST_4KB      2097152      1  thrpt   10  1412321.440 ± 188738.874  ops/min
MicroLargePages.micro_HOP_DIST_4KB      2097152      2  thrpt   10   515607.542 ±   2258.591  ops/min
MicroLargePages.micro_HOP_DIST_4KB      2097152      4  thrpt   10   303250.463 ±   2862.549  ops/min

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PR: https://git.openjdk.java.net/jdk/pull/7326