[crac] RFR: Wait until G1 GC has finished before creating a snapshot.

[Jan Kratochvil]

@rvansa did report his snapshots are about 2x-3x bigger than they should be. He then also found it only happens if the snapshot is done too quickly after GC should have been run.

One can reproduce the race case by:

--- a/src/hotspot/share/gc/g1/g1UncommitRegionTask.hpp
+++ b/src/hotspot/share/gc/g1/g1UncommitRegionTask.hpp
@@ -35,7 +35,7 @@ class G1UncommitRegionTask : public G1ServiceTask {
   // is short, while still making reasonable progress.
   static const uint UncommitSizeLimit = 128 * M;
   // Initial delay in milliseconds after GC before the regions are uncommitted.
-  static const uint UncommitInitialDelayMs = 100;
+  static const uint UncommitInitialDelayMs = 10*1000;
   // The delay between two uncommit task executions.
   static const uint UncommitTaskDelayMs = 10;

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

Commit messages:
 - Wait until G1 GC has finished before creating a snapshot.

Changes: https://git.openjdk.org/crac/pull/93/files
 Webrev: https://webrevs.openjdk.org/?repo=crac&pr=93&range=00
  Stats: 20 lines in 3 files changed: 20 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/crac/pull/93.diff
  Fetch: git fetch https://git.openjdk.org/crac.git pull/93/head:pull/93

PR: https://git.openjdk.org/crac/pull/93