[RocksDB] Add score column to leveldb.stats

Summary: Added the 'score' column to the compaction stats output, which shows the level total size devided by level target size. Could be useful when monitoring compaction decisions...

Test Plan: make check; db_bench

Reviewers: dhruba

CC: leveldb, MarkCallaghan

Differential Revision: https://reviews.facebook.net/D11025

db/db_impl.cc

@@ -2388,8 +2388,8 @@ bool DBImpl::GetProperty(const Slice& property, std::string* value) {
     // Pardon the long line but I think it is easier to read this way.
     snprintf(buf, sizeof(buf),
              "                               Compactions\n"
-             "Level  Files Size(MB) Time(sec)  Read(MB) Write(MB)    Rn(MB)  Rnp1(MB)  Wnew(MB) Amplify Read(MB/s) Write(MB/s)      Rn     Rnp1     Wnp1     NewW    Count  Ln-stall\n"
-             "----------------------------------------------------------------------------------------------------------------------------------------------------------------------\n"
+             "Level  Files Size(MB) Score Time(sec)  Read(MB) Write(MB)    Rn(MB)  Rnp1(MB)  Wnew(MB) Amplify Read(MB/s) Write(MB/s)      Rn     Rnp1     Wnp1     NewW    Count  Ln-stall\n"
+             "----------------------------------------------------------------------------------------------------------------------------------------------------------------------------\n"
              );
     value->append(buf);
     for (int level = 0; level < NumberLevels(); level++) {
@@ -2407,10 +2407,12 @@ bool DBImpl::GetProperty(const Slice& property, std::string* value) {
         total_bytes += bytes_read + stats_[level].bytes_written;
         snprintf(
             buf, sizeof(buf),
-            "%3d %8d %8.0f %9.0f %9.0f %9.0f %9.0f %9.0f %9.0f %7.1f %9.1f %11.1f %8d %8d %8d %8d %8d %9.1f\n",
+            "%3d %8d %8.0f %5.1f %9.0f %9.0f %9.0f %9.0f %9.0f %9.0f %7.1f %9.1f %11.1f %8d %8d %8d %8d %8d %9.1f\n",
             level,
             files,
             versions_->NumLevelBytes(level) / 1048576.0,
+            versions_->NumLevelBytes(level) /
+            versions_->MaxBytesForLevel(level),
             stats_[level].micros / 1e6,
             bytes_read / 1048576.0,
             stats_[level].bytes_written / 1048576.0,

db/version_set.h

@@ -381,6 +381,8 @@ class VersionSet {
   // Get the max file size in a given level.
   uint64_t MaxFileSizeForLevel(int level);
 
+  double MaxBytesForLevel(int level);
+
  private:
   class Builder;
   struct ManifestWriter;
@@ -410,8 +412,6 @@ class VersionSet {
 
   bool ManifestContains(const std::string& record) const;
 
-  double MaxBytesForLevel(int level);
-
   int64_t ExpandedCompactionByteSizeLimit(int level);
 
   int64_t MaxGrandParentOverlapBytes(int level);