RFR: 8351661: NMT: VMATree should support separate call-stacks for reserve and commit operations [v8]

[Gerard Ziemski]

On Mon, 7 Apr 2025 12:37:30 GMT, Afshin Zafari <azafari at openjdk.org> wrote:

>> In NMT detail mode, we need to have separate call-stacks for Reserve and Commit operations.
>> This PR adds a second stack to every node that will be used when committing (and uncommitting) the start node of a reserved region.
>
> Afshin Zafari has updated the pull request incrementally with one additional commit since the last revision:
> 
>   fixes. New check_tree impl and visualization.

I really like the way we now visualize the cases. One thing I'd prefer is to actually have the "pre" and "post" cases spelled out explicitly, which I did (and aligned the visual snapshots where needed)

NIce!

test/hotspot/gtest/nmt/test_vmatree.cpp line 862:

> 860:     tree.commit_mapping(25, 25, call_stack_2, true); // commit at the middle of the region
> 861:     // Pre: post of previous
> 862:     // Post: .........0---------25*********50--------100.........

// Pre:  .........0------------------------------100.........
    // Post: .........0---------25*********50--------100.........

test/hotspot/gtest/nmt/test_vmatree.cpp line 876:

> 874:     tree.commit_mapping(0, 20, call_stack_2, true); // commit at the begin of the region
> 875:     // Pre: post of previous
> 876:     // Post: .........0********20---------25********50--------100.........

// Pre:  .........0---------------25*********50--------100.........
    // Post: .........0********20-----25*********50--------100.........

test/hotspot/gtest/nmt/test_vmatree.cpp line 890:

> 888:     tree.commit_mapping(80, 20, call_stack_2, true); // commit at the end of the region
> 889:     // Pre: post of previous
> 890:     // Post: .........0********20---------25********50--------80********100.........

// Pre:  .........0********20-----25*********50------------------100.........
    // Post: .........0********20-----25*********50--------80********100.........

test/hotspot/gtest/nmt/test_vmatree.cpp line 920:

> 918:     tree.commit_mapping(20, 20, call_stack_2, true);
> 919:     // Pre: post of previous
> 920:     // Post: .........0---------20********40-------100.........

// Pre:  .........0----------------------------100.........
    // Post: .........0---------20********40-------100.........

test/hotspot/gtest/nmt/test_vmatree.cpp line 937:

> 935:     tree.commit_mapping(10, 20, call_stack_3);
> 936:     // Pre: post of previous
> 937:     // Post: .........0---------10********30********40-------100.........

// Pre:  .........0---------20**************40-------100.........
    // Post: .........0---10*********30*********40-------100.........

test/hotspot/gtest/nmt/test_vmatree.cpp line 954:

> 952:     tree.commit_mapping(30, 20, call_stack_4);
> 953:     // Pre: post of previous
> 954:     // Post: .........0---------10********30********50-------100.........

// Pre:  .........0---------10********30*********40------------------100.........
    // Post: .........0---------10********30********************50-------100.........

test/hotspot/gtest/nmt/test_vmatree.cpp line 975:

> 973: 
> 974:     tree.uncommit_mapping(0, 5, call_stack_2);
> 975:     // Pre:  .........0********10--------20********40-------100.........

// Pre:  .........0***********10--------20********40-------100.........

test/hotspot/gtest/nmt/test_vmatree.cpp line 980:

> 978:     //        -         si_1      si_1      si_1      si_1      -
> 979:     //        -         si_2      -         si_2      -         -
> 980:     // Post: .........0--------5********10--------20********40-------100.........

// Post: .........0-----5*****10--------20********40-------100.........

test/hotspot/gtest/nmt/test_vmatree.cpp line 994:

> 992:     tree.uncommit_mapping(20, 10, call_stack_2);
> 993:     // Pre: post of previous
> 994:     // Post: .........0--------5********10--------30********40-------100.........

// Pre:  .........0-----5*****10--------20****************40-------100.........
    // Post: .........0-----5*****10----------------30********40-------100.........

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

Changes requested by gziemski (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/24028#pullrequestreview-2747343623
PR Review Comment: https://git.openjdk.org/jdk/pull/24028#discussion_r2031552088
PR Review Comment: https://git.openjdk.org/jdk/pull/24028#discussion_r2031552929
PR Review Comment: https://git.openjdk.org/jdk/pull/24028#discussion_r2031553434
PR Review Comment: https://git.openjdk.org/jdk/pull/24028#discussion_r2031554000
PR Review Comment: https://git.openjdk.org/jdk/pull/24028#discussion_r2031554533
PR Review Comment: https://git.openjdk.org/jdk/pull/24028#discussion_r2031554915
PR Review Comment: https://git.openjdk.org/jdk/pull/24028#discussion_r2031555378
PR Review Comment: https://git.openjdk.org/jdk/pull/24028#discussion_r2031556001
PR Review Comment: https://git.openjdk.org/jdk/pull/24028#discussion_r2031556524