Crashtest mempurge (#8545)

Summary:
Add `experiemental_allow_mempurge` flag support for `db_stress` and `db_crashtest.py`, with a `false` default value.
I succesfully tested locally both `whitebox` and `blackbox` crash tests with `experiemental_allow_mempurge` flag set as true.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8545

Reviewed By: akankshamahajan15

Differential Revision: D29734513

Pulled By: bjlemaire

fbshipit-source-id: 24316c0eccf6caf409e95c035f31d822c66714ae

db_stress_tool/db_stress_common.h

@@ -141,6 +141,7 @@ DECLARE_uint64(subcompactions);
 DECLARE_uint64(periodic_compaction_seconds);
 DECLARE_uint64(compaction_ttl);
 DECLARE_bool(allow_concurrent_memtable_write);
+DECLARE_bool(experimental_allow_mempurge);
 DECLARE_bool(enable_write_thread_adaptive_yield);
 DECLARE_int32(reopen);
 DECLARE_double(bloom_bits);

db_stress_tool/db_stress_gflags.cc

@@ -326,6 +326,9 @@ DEFINE_uint64(compaction_ttl, 1000,
 DEFINE_bool(allow_concurrent_memtable_write, false,
             "Allow multi-writers to update mem tables in parallel.");
 
+DEFINE_bool(experimental_allow_mempurge, false,
+            "Allow mempurge process to collect memtable garbage bytes.");
+
 DEFINE_bool(enable_write_thread_adaptive_yield, true,
             "Use a yielding spin loop for brief writer thread waits.");
 

db_stress_tool/db_stress_test_base.cc

@@ -2259,6 +2259,7 @@ void StressTest::Open() {
     options_.max_subcompactions = static_cast<uint32_t>(FLAGS_subcompactions);
     options_.allow_concurrent_memtable_write =
         FLAGS_allow_concurrent_memtable_write;
+    options_.experimental_allow_mempurge = FLAGS_experimental_allow_mempurge;
     options_.periodic_compaction_seconds = FLAGS_periodic_compaction_seconds;
     options_.ttl = FLAGS_compaction_ttl;
     options_.enable_pipelined_write = FLAGS_enable_pipelined_write;

tools/db_crashtest.py

@@ -220,6 +220,7 @@ whitebox_default_params = {
 simple_default_params = {
     "allow_concurrent_memtable_write": lambda: random.randint(0, 1),
     "column_families": 1,
+    "experimental_allow_mempurge": 0,
     "max_background_compactions": 1,
     "max_bytes_for_level_base": 67108864,
     "memtablerep": "skip_list",