On Thu, 4 Sep 2025 14:19:06 GMT, Stefan Johansson <sjoha...@openjdk.org> wrote:
> Please review this enhancement to the smaps parser and printer. > > **Summary** > While working on [JDK-8366434](https://bugs.openjdk.org/browse/JDK-8366434) > one idea for a test to verify if the heap CAN be backed by transparent huge > pages (THP) was to use PrintMemoryMapAtExit and look at the tags printed for > JAVAHEAP. > > It turns out this worked in most cases but on systems where the THP mode is > configured as 'always' but there are no huge pages available for use, the > JAVAHEAP line will not show any indication that it can be backed by huge > pages. > > For this to be possible we need to parse the field THPeligible as well and > include this information in the printouts. With this change we now parse the > THPeligible field and tag mapping that are THP eligible with `thpel`. We skip > this tag for mappings that are tagged with `thpad` (madvised with > MADV_HUGEPAGE) to avoid too much THP info on one mapping. > > **Testing** > * Mach5 testing with the existing test showed a need to update the regex for > verifying Metaspace and the fix have been tested manually locally as well as > in Mach5. src/hotspot/os/linux/procMapsParser.hpp line 52: > 50: size_t anonhugepages; > 51: size_t swap; > 52: size_t thpeligible; Why `size`? Its name sounds like `bool`? ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/27098#discussion_r2322987857
