RFR: 8337517: Redacted Heap Dumps

[Aleksey Shipilev]

On Wed, 31 Jul 2024 19:10:41 GMT, Henry Lin <duke at openjdk.org> wrote:

> Adds a command line option `-redact` to `jcmd`, `redact` to `jmap` and `-XX:+HeapDumpRedacted` enabling redacted heap dumps. When enabled, the output binary heap dump has zeroes written out in place of the original primitive values in the object fields. There is a new jtreg test `heapDumpRedactedTest.java` that tests that the fields are properly redacted.

Looks interesting, some suggestions:

src/hotspot/share/services/heapDumper.cpp line 999:

> 997: 
> 998: // dumps the raw value of the given field
> 999: void DumperSupport::dump_field_value(AbstractDumpWriter* writer, char type, oop obj, int offset, bool redact) {

I think it would be cleaner to specialize this method into two: `dump_field_value` and `dump_redacted_field_value`, and dispatch to it from outside. Likely saves branches.

src/hotspot/share/services/heapDumper.cpp line 1386:

> 1384: 
> 1385:   if (redact) {
> 1386:     writer->write_raw(nullptr, length_in_bytes); //nullptr to write zeros

Would be easier to just:


  if (redact) {
    writer->write_raw(nullptr, length_in_bytes); //nullptr to write zeros
    writer->end_sub_record();
    return;
  }


...and leave the rest of the code alone.

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

PR Review: https://git.openjdk.org/jdk/pull/20409#pullrequestreview-2212939599
PR Review Comment: https://git.openjdk.org/jdk/pull/20409#discussion_r1700262770
PR Review Comment: https://git.openjdk.org/jdk/pull/20409#discussion_r1700258753