On Thu, 4 Sep 2025 17:56:56 GMT, Albert Mingkun Yang <ay...@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`? Yes, it works like a `bool` but I represented it as a number to simply do the parsing similar to the other fields, but I guess I could handle it more like how `VmFlags` are handled. The the parsing would then look like this, would you prefer that: if (strncmp(_line, "THPeligible:", 12) == 0) { out.thpeligible = ::strstr(_line + 12, "1") != nullptr; return; } I think I would =) ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/27098#discussion_r2324211968
