RFR: 8351661: NMT: VMATree should support separate call-stacks for reserve and commit operations [v2]

[Afshin Zafari]

On Thu, 13 Mar 2025 13:13:15 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:
> 
>   fixed a bug.

The cases and their result:

// (address, size, callstack) arguments

// x == invalid stack == not-filled

# Case 1
tree.reserve(0, 100, s1);
tree.commit(25, 25 , s2);
    0       25         50         100
--------  --------  --------  --------
in   out  in   out  in   out  in   out 
x    s1   s1   s2   s2   x    s1   x
x    x    x    x    x    x     x   x

commit is not at start of the region.

# Case 2
tree.reserve(0, 100, s1);
tree.reserve(10, 10, s2);
    0       10         20         100
--------  --------  --------  --------
in   out  in   out  in   out  in   out 
x    s1   s1   s2   s2   x    s1   x
x    x    x    x    x    x     x   x

# Case 3
tree.commit(0, 100, s1);
    0       100  
--------  --------
in   out  in   out
x    s1   s1   x 
x    x    x    x  

it is not acceptable to committ a region without reserving it.

# Case 4
tree.commit(0, 100, s1);
tree.reserve(0, 100, s2);
    0       100  
--------  --------
in   out  in   out
x    s2   s2   x 
x    s1   s1   x

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

PR Comment: https://git.openjdk.org/jdk/pull/24028#issuecomment-2732247346