[GitHub] [incubator-pegasus] hycdong commented on a change in pull request #774: feat: add read/write amp perf-counter support

[GitBox <gi...@apache.org>]

hycdong commented on a change in pull request #774:
URL: https://github.com/apache/incubator-pegasus/pull/774#discussion_r658507052



##########
File path: src/server/pegasus_server_impl.cpp
##########
@@ -46,6 +46,7 @@ namespace pegasus {
 namespace server {
 
 DEFINE_TASK_CODE(LPC_PEGASUS_SERVER_DELAY, TASK_PRIORITY_COMMON, ::dsn::THREAD_POOL_DEFAULT)
+DSN_DECLARE_int32(read_amp_bytes_per_bit);

Review comment:
       I suggest this config mutable.

##########
File path: src/server/pegasus_server_impl.cpp
##########
@@ -2274,6 +2289,33 @@ void pegasus_server_impl::update_replica_rocksdb_statistics()
     dinfo_replica("_pfc_rdb_bf_point_negatives: {}", bf_point_negatives);
 }
 
+void pegasus_server_impl::update_replica_rocksdb_amp_statistics()
+{
+    // Update _pfc_rdb_write_amplification
+    std::map<std::string, std::string> props;
+    if (_db->GetMapProperty(_data_cf, "rocksdb.cfstats", &props)) {
+        auto write_amplification_iter = props.find("compaction.Sum.WriteAmp");
+        auto write_amplification = write_amplification_iter == props.end()
+                                       ? 1
+                                       : std::stod(write_amplification_iter->second);
+        _pfc_rdb_write_amplification->set(write_amplification);
+        dinfo_replica("_pfc_rdb_write_amplification: {}", write_amplification);
+    }
+
+    // Update _pfc_rdb_read_amplification
+    if (FLAGS_read_amp_bytes_per_bit > 0) {
+        auto estimate_useful_bytes =
+            _statistics->getTickerCount(rocksdb::READ_AMP_ESTIMATE_USEFUL_BYTES);

Review comment:
       https://github.com/facebook/rocksdb/blob/v6.6.4/monitoring/statistics.cc
   I notice that there are other statistics similar to what we like, such as `GET_HIT_L0`, `GET_HIT_L1`, `GET_HIT_L2_AND_UP`, what it the difference between them?




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