RFR: 8322475: Extend printing for System.map [v6]

[Severin Gehwolf]

On Thu, 20 Jun 2024 09:31:48 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

>> This is an expansion on the new `System.map` command introduced with JDK-8318636.
>> 
>> We now print valuable information per memory region, such as:
>> 
>> - the actual resident set size
>> - the actual number of huge pages
>> - the actual used page size
>> - the THP state of the region (was advised, is eligible, uses THP, ...)
>> - whether the region is shared
>> - whether the region had been committed (backed by swap)
>> - whether the region has been swapped out.
>> 
>> Example output:
>> 
>> [system-map-thp1.txt](https://github.com/user-attachments/files/15587748/system-map-thp1.txt)
>> 
>> 
>> from                 to                       size        rss    hugetlb pgsz prot notes            vm info/file                                                                                                                                                                    
>> 0x00000000c0000000 - 0x00000000ffe00000 1071644672          0    4194304 2M   rw-p huge             JAVAHEAP /anon_hugepage                                                                                                                                                         
>> 0x00000000ffe00000 - 0x0000000100000000    2097152          0          0 2M   rw-p huge             JAVAHEAP /anon_hugepage                                                                                                                                                         
>> 0x0000558016b67000 - 0x0000558016b68000       4096       4096          0 4K   r--p                  /shared/projects/openjdk/jdk-jdk/output-fastdebug/images/jdk/bin/java
>> 0x0000558016b68000 - 0x0000558016b69000       4096       4096          0 4K   r-xp                  /shared/projects/openjdk/jdk-jdk/output-fastdebug/images/jdk/bin/java
>> 0x00007f3a749f2000 - 0x00007f3a74c62000    2555904    2555904          0 4K   rwxp                  CODE(CodeHeap 'profiled nmethods')                               
>> 0x00007f3a74c62000 - 0x00007f3a7be51000  119468032          0          0 4K   ---p nores            CODE(CodeHeap 'profiled nmethods')                               
>> 0x00007f3a7be51000 - 0x00007f3a7c1c1000    3604480    3604480          0 4K   rwxp                  CODE(CodeHeap 'profiled nmethods')                               
>> 0x00007f3a7c1c1000 - 0x00007f3a7c592000    4001792          0          0 4K   ---p nores            CODE(CodeHeap 'non-nmethods')                                    
>> 0x00007f3a7c592000 - 0x00007f3a7c802000    2555904    2...
>
> Thomas Stuefe has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 23 commits:
> 
>  - feedback johan
>  - fix merge errors
>  - Merge branch 'master' into System.maps-more-info
>  - copyrights
>  - Merge branch 'master' into System.maps-more-info
>  - fix merge issue
>  - Merge branch 'master' into System.maps-more-info
>  - fix whitespace issue
>  - wip
>  - exhuming
>  - ... and 13 more: https://git.openjdk.org/jdk/compare/c6f3bf4b...940199de

This seems fine. Mostly nits.

src/hotspot/os/linux/procMapsParser.hpp line 66:

> 64:     from = to = nullptr;
> 65:     prot[0] = filename[0] = '\0';
> 66:     kernelpagesize = rss = private_hugetlb = anonhugepages = swap = 0;

`private_hugetlb` and `shared_hugetlb` missing in reset. Intentional?

src/hotspot/share/nmt/memMapPrinter.cpp line 262:

> 260:             print_thread_details_for_supposed_stack_address(vma_from, vma_to, _out);
> 261:           }
> 262:           num_printed ++;

Style: No space before `++`.

test/hotspot/jtreg/serviceability/dcmd/vm/SystemDumpMapTest.java line 31:

> 29: 
> 30: import java.io.*;
> 31: import java.lang.StringBuilder;

Nit: `java.lang.*` are imported by default. I don't see it used, so maybe a left over?

test/hotspot/jtreg/serviceability/dcmd/vm/SystemMapTestBase.java line 53:

> 51:         regexBase_committed + "\\[stack\\]",
> 52:         // we should see the hs-perf data file, and it should appear as shared as well as committed
> 53:         regexBase_shared_and_committed + "hsperfdata_.*"

Suggestion: Should the test run with `-XX:+UsePerfData` since it's expecting this file. It's default on, but that might change.

-------------

PR Review: https://git.openjdk.org/jdk/pull/17158#pullrequestreview-2154058332
PR Review Comment: https://git.openjdk.org/jdk/pull/17158#discussion_r1662723988
PR Review Comment: https://git.openjdk.org/jdk/pull/17158#discussion_r1662661856
PR Review Comment: https://git.openjdk.org/jdk/pull/17158#discussion_r1662705054
PR Review Comment: https://git.openjdk.org/jdk/pull/17158#discussion_r1662700550