Integrate block cache tracing into db_bench (#5459)

Summary:
This PR integrates the block cache tracing into db_bench. It adds three command line arguments.
-block_cache_trace_file (Block cache trace file path.) type: string default: ""
-block_cache_trace_max_trace_file_size_in_bytes (The maximum block cache
trace file size in bytes. Block cache accesses will not be logged if the
trace file size exceeds this threshold. Default is 64 GB.) type: int64
default: 68719476736
-block_cache_trace_sampling_frequency (Block cache trace sampling
frequency, termed s. It uses spatial downsampling and samples accesses to
one out of s blocks.) type: int32 default: 1
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5459

Differential Revision: D15832031

Pulled By: HaoyuHuang

fbshipit-source-id: 0ecf2f2686557251fe741a2769b21170777efa3d

tools/db_bench_tool.cc

@@ -774,6 +774,17 @@ DEFINE_string(trace_file, "", "Trace workload to a file. ");
 DEFINE_int32(trace_replay_fast_forward, 1,
              "Fast forward trace replay, must >= 1. ");
 
+DEFINE_int32(block_cache_trace_sampling_frequency, 1,
+             "Block cache trace sampling frequency, termed s. It uses spatial "
+             "downsampling and samples accesses to one out of s blocks.");
+DEFINE_int64(
+    block_cache_trace_max_trace_file_size_in_bytes,
+    uint64_t{64} * 1024 * 1024 * 1024,
+    "The maximum block cache trace file size in bytes. Block cache accesses "
+    "will not be logged if the trace file size exceeds this threshold. Default "
+    "is 64 GB.");
+DEFINE_string(block_cache_trace_file, "", "Block cache trace file path.");
+
 static enum rocksdb::CompressionType StringToCompressionType(const char* ctype) {
   assert(ctype);
 
@@ -2081,6 +2092,7 @@ class Benchmark {
   Options open_options_;  // keep options around to properly destroy db later
 #ifndef ROCKSDB_LITE
   TraceOptions trace_options_;
+  TraceOptions block_cache_trace_options_;
 #endif
   int64_t reads_;
   int64_t deletes_;
@@ -2917,6 +2929,47 @@ class Benchmark {
           fprintf(stdout, "Tracing the workload to: [%s]\n",
                   FLAGS_trace_file.c_str());
         }
+        // Start block cache tracing.
+        if (!FLAGS_block_cache_trace_file.empty()) {
+          // Sanity checks.
+          if (FLAGS_block_cache_trace_sampling_frequency <= 0) {
+            fprintf(stderr,
+                    "Block cache trace sampling frequency must be higher than "
+                    "0.\n");
+            exit(1);
+          }
+          if (FLAGS_block_cache_trace_max_trace_file_size_in_bytes <= 0) {
+            fprintf(stderr,
+                    "The maximum file size for block cache tracing must be "
+                    "higher than 0.\n");
+            exit(1);
+          }
+          block_cache_trace_options_.max_trace_file_size =
+              FLAGS_block_cache_trace_max_trace_file_size_in_bytes;
+          block_cache_trace_options_.sampling_frequency =
+              FLAGS_block_cache_trace_sampling_frequency;
+          std::unique_ptr<TraceWriter> block_cache_trace_writer;
+          Status s = NewFileTraceWriter(FLAGS_env, EnvOptions(),
+                                        FLAGS_block_cache_trace_file,
+                                        &block_cache_trace_writer);
+          if (!s.ok()) {
+            fprintf(stderr,
+                    "Encountered an error when creating trace writer, %s\n",
+                    s.ToString().c_str());
+            exit(1);
+          }
+          s = db_.db->StartBlockCacheTrace(block_cache_trace_options_,
+                                           std::move(block_cache_trace_writer));
+          if (!s.ok()) {
+            fprintf(
+                stderr,
+                "Encountered an error when starting block cache tracing, %s\n",
+                s.ToString().c_str());
+            exit(1);
+          }
+          fprintf(stdout, "Tracing block cache accesses to: [%s]\n",
+                  FLAGS_block_cache_trace_file.c_str());
+        }
 #endif  // ROCKSDB_LITE
 
         if (num_warmup > 0) {
@@ -2959,6 +3012,14 @@ class Benchmark {
                 s.ToString().c_str());
       }
     }
+    if (!FLAGS_block_cache_trace_file.empty()) {
+      Status s = db_.db->EndBlockCacheTrace();
+      if (!s.ok()) {
+        fprintf(stderr,
+                "Encountered an error ending the block cache tracing, %s\n",
+                s.ToString().c_str());
+      }
+    }
 #endif  // ROCKSDB_LITE
 
     if (FLAGS_statistics) {