Differences to original CSR:

The original CSR was about removing the sub-option. That was fine for a head release.

This CSR, aimed at a maintenance release, proposes to deprecate it instead:

• jcmd would still accept the "shutdown" sub option and return 0 as exit code.
• But jcmd should report "This option has been deprecated" instead of "NMT is shutting down"

Summary

Deprecate NMT shutdown jcmd command option

Problem

The functionality to shutdown NMT is a remnant of its first implementation, which could consume an excessive amount of memory for tracking itself. This is no longer a problem in the current implementation. Since the shutdown ability causes unnecessary complexity, we will remove it.

The jcmd VM.native_memory provides the shutdown sub-option as a user-facing frontend of NMT shutdown. It had been rarely used and should be removed as well.

Solution

Deprecate and remove the shutdownsub-option of the VM.native_memory jcmd.

Specification

Remove shutdown jcmd command.

diff --git a/src/hotspot/share/services/nmtDCmd.cpp b/src/hotspot/share/services/nmtDCmd.cpp
index e89dd2c56e7..dd8eb17c298 100644
--- a/src/hotspot/share/services/nmtDCmd.cpp
+++ b/src/hotspot/share/services/nmtDCmd.cpp
@@ -147,9 +139,6 @@ void NMTDCmd::execute(DCmdSource source, TRAPS) {
     } else {
       output()->print_cr("No detail baseline for comparison");
     }
   } else if (_shutdown.value()) {
-    MemTracker::shutdown();
-    output()->print_cr("Native memory tracking has been turned off");
+    output()->print_cr("Shutdown sub command has been deprecated.");
   } else if (_statistics.value()) {
     if (check_detail_tracking_level(output())) {
       MemTracker::tuning_statistics(output());