[RocksDB] Expose compaction stalls via db_statistics

Test Plan: make check

Reviewers: dhruba, haobo

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D10575

db/db_impl.cc

@@ -2183,6 +2183,7 @@ Status DBImpl::MakeRoomForWrite(bool force) {
       uint64_t t1 = env_->NowMicros();
       env_->SleepForMicroseconds(1000);
       uint64_t delayed = env_->NowMicros() - t1;
+      RecordTick(options_.statistics, STALL_L0_SLOWDOWN_MICROS, delayed);
       stall_level0_slowdown_ += delayed;
       allow_delay = false;  // Do not delay a single write more than once
       //Log(options_.info_log,
@@ -2204,7 +2205,9 @@ Status DBImpl::MakeRoomForWrite(bool force) {
       Log(options_.info_log, "wait for memtable compaction...\n");
       uint64_t t1 = env_->NowMicros();
       bg_cv_.Wait();
-      stall_memtable_compaction_ += env_->NowMicros() - t1;
+      const uint64_t stall = env_->NowMicros() -t1;
+      RecordTick(options_.statistics, STALL_MEMTABLE_COMPACTION_MICROS, stall);
+      stall_memtable_compaction_ += stall;
     } else if (versions_->NumLevelFiles(0) >=
                options_.level0_stop_writes_trigger) {
       // There are too many level-0 files.
@@ -2212,7 +2215,9 @@ Status DBImpl::MakeRoomForWrite(bool force) {
       uint64_t t1 = env_->NowMicros();
       Log(options_.info_log, "wait for fewer level0 files...\n");
       bg_cv_.Wait();
-      stall_level0_num_files_ += env_->NowMicros() - t1;
+      const uint64_t stall = env_->NowMicros() - t1;
+      RecordTick(options_.statistics, STALL_L0_NUM_FILES_MICROS, stall);
+      stall_level0_num_files_ += stall;
     } else if (
         allow_rate_limit_delay &&
         options_.rate_limit > 1.0 &&
@@ -2225,7 +2230,9 @@ Status DBImpl::MakeRoomForWrite(bool force) {
       uint64_t delayed = env_->NowMicros() - t1;
       stall_leveln_slowdown_[max_level] += delayed;
       // Make sure the following value doesn't round to zero.
-      rate_limit_delay_millis += std::max((delayed / 1000), (uint64_t) 1);
+      uint64_t rate_limit = std::max((delayed / 1000), (uint64_t) 1);
+      rate_limit_delay_millis += rate_limit;
+      RecordTick(options_.statistics, RATE_LIMIT_DELAY_MILLIS, rate_limit);
       if (rate_limit_delay_millis >=
           (unsigned)options_.rate_limit_delay_milliseconds) {
         allow_rate_limit_delay = false;

include/leveldb/statistics.h

@@ -40,7 +40,14 @@ enum Tickers {
   NO_FILE_CLOSES = 10,
   NO_FILE_OPENS = 11,
   NO_FILE_ERRORS = 12,
-  TICKER_ENUM_MAX = 13,
+  // Time system had to wait to do LO-L1 compactions
+  STALL_L0_SLOWDOWN_MICROS = 13,
+  // Time system had to wait to move memtable to L1.
+  STALL_MEMTABLE_COMPACTION_MICROS = 14,
+  // write throttle because of too many files in L0
+  STALL_L0_NUM_FILES_MICROS = 15,
+  RATE_LIMIT_DELAY_MILLIS = 16,
+  TICKER_ENUM_MAX = 17
 };