Temporarily disable mempurge in crash test (#10252)

Summary:
Need to disable it for now as CI is failing, particularly `MultiOpsTxnsStressTest`. Investigation details in internal task T124324915. This PR disables mempurge more widely than `MultiOpsTxnsStressTest` until we know the issue is contained to that particular test.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/10252

Reviewed By: riversand963

Differential Revision: D37432948

Pulled By: ajkr

fbshipit-source-id: d0cf5b0e0ec7c3142c382a0347f35a4c34f4607a

db_stress_tool/db_stress_test_base.cc

@@ -193,7 +193,8 @@ bool StressTest::BuildOptionsTable() {
       {"memtable_huge_page_size", {"0", std::to_string(2 * 1024 * 1024)}},
       {"max_successive_merges", {"0", "2", "4"}},
       {"inplace_update_num_locks", {"100", "200", "300"}},
-      {"experimental_mempurge_threshold", {"0.0", "1.0"}},
+      // TODO: re-enable once internal task T124324915 is fixed.
+      // {"experimental_mempurge_threshold", {"0.0", "1.0"}},
       // TODO(ljin): enable test for this option
       // {"disable_auto_compactions", {"100", "200", "300"}},
       {"level0_file_num_compaction_trigger",

tools/db_crashtest.py

@@ -275,7 +275,8 @@ whitebox_default_params = {
 simple_default_params = {
     "allow_concurrent_memtable_write": lambda: random.randint(0, 1),
     "column_families": 1,
-    "experimental_mempurge_threshold": lambda: 10.0*random.random(),
+    # TODO: re-enable once internal task T124324915 is fixed.
+    # "experimental_mempurge_threshold": lambda: 10.0*random.random(),
     "max_background_compactions": 1,
     "max_bytes_for_level_base": 67108864,
     "memtablerep": "skip_list",