diff --git a/db/builder.cc b/db/builder.cc
index a3ed607bf..2a33bb008 100644
--- a/db/builder.cc
+++ b/db/builder.cc
@@ -21,6 +21,8 @@
 #include "rocksdb/options.h"
 #include "rocksdb/table.h"
 #include "table/block_based_table_builder.h"
+#include "util/iostats_context_imp.h"
+#include "util/thread_status_util.h"
 #include "util/stop_watch.h"
 
 namespace rocksdb {
@@ -52,6 +54,8 @@ Status BuildTable(
     const CompressionType compression,
     const CompressionOptions& compression_opts, bool paranoid_file_checks,
     const Env::IOPriority io_priority, TableProperties* table_properties) {
+  // Reports the IOStats for flush for every following bytes.
+  const size_t kReportFlushIOStatsEvery = 1048576;
   Status s;
   meta->fd.file_size = 0;
   meta->smallest_seqno = meta->largest_seqno = 0;
@@ -176,6 +180,13 @@ Status BuildTable(
           }
         }
 
+        if (io_priority == Env::IO_HIGH &&
+            IOSTATS(bytes_written) >= kReportFlushIOStatsEvery) {
+          ThreadStatusUtil::IncreaseThreadOperationProperty(
+              ThreadStatus::FLUSH_BYTES_WRITTEN,
+              IOSTATS(bytes_written));
+          IOSTATS_RESET(bytes_written);
+        }
         if (!iterator_at_next) iter->Next();
       }
 
@@ -193,6 +204,13 @@ Status BuildTable(
         SequenceNumber seqno = GetInternalKeySeqno(key);
         meta->smallest_seqno = std::min(meta->smallest_seqno, seqno);
         meta->largest_seqno = std::max(meta->largest_seqno, seqno);
+        if (io_priority == Env::IO_HIGH &&
+            IOSTATS(bytes_written) >= kReportFlushIOStatsEvery) {
+          ThreadStatusUtil::IncreaseThreadOperationProperty(
+              ThreadStatus::FLUSH_BYTES_WRITTEN,
+              IOSTATS(bytes_written));
+          IOSTATS_RESET(bytes_written);
+        }
       }
     }
 
diff --git a/db/flush_job.cc b/db/flush_job.cc
index c0745cc64..0f6c85f9b 100644
--- a/db/flush_job.cc
+++ b/db/flush_job.cc
@@ -82,8 +82,7 @@ FlushJob::FlushJob(const std::string& dbname, ColumnFamilyData* cfd,
       stats_(stats),
       event_logger_(event_logger) {
   // Update the thread status to indicate flush.
-  ThreadStatusUtil::SetColumnFamily(cfd_);
-  ThreadStatusUtil::SetThreadOperation(ThreadStatus::OP_FLUSH);
+  ReportStartedFlush();
   TEST_SYNC_POINT("FlushJob::FlushJob()");
 }
 
@@ -92,6 +91,31 @@ FlushJob::~FlushJob() {
   ThreadStatusUtil::ResetThreadStatus();
 }
 
+void FlushJob::ReportStartedFlush() {
+  ThreadStatusUtil::SetColumnFamily(cfd_);
+  ThreadStatusUtil::SetThreadOperation(ThreadStatus::OP_FLUSH);
+  ThreadStatusUtil::SetThreadOperationProperty(
+      ThreadStatus::COMPACTION_JOB_ID,
+      job_context_->job_id);
+  IOSTATS_RESET(bytes_written);
+}
+
+void FlushJob::ReportFlushInputSize(const autovector<MemTable*>& mems) {
+  uint64_t input_size = 0;
+  for (auto* mem : mems) {
+    input_size += mem->ApproximateMemoryUsage();
+  }
+  ThreadStatusUtil::IncreaseThreadOperationProperty(
+      ThreadStatus::FLUSH_BYTES_MEMTABLES,
+      input_size);
+}
+
+void FlushJob::RecordFlushIOStats() {
+  ThreadStatusUtil::IncreaseThreadOperationProperty(
+      ThreadStatus::FLUSH_BYTES_WRITTEN, IOSTATS(bytes_written));
+  IOSTATS_RESET(bytes_written);
+}
+
 Status FlushJob::Run(uint64_t* file_number) {
   AutoThreadOperationStageUpdater stage_run(
       ThreadStatus::STAGE_FLUSH_RUN);
@@ -105,6 +129,7 @@ Status FlushJob::Run(uint64_t* file_number) {
     return Status::OK();
   }
 
+  ReportFlushInputSize(mems);
 
   // entries mems are (implicitly) sorted in ascending order by their created
   // time. We will use the first memtable's `edit` to keep the meta info for
@@ -138,6 +163,7 @@ Status FlushJob::Run(uint64_t* file_number) {
   if (s.ok() && file_number != nullptr) {
     *file_number = fn;
   }
+  RecordFlushIOStats();
 
   auto stream = event_logger_->LogToBuffer(log_buffer_);
   stream << "job" << job_context_->job_id << "event"
diff --git a/db/flush_job.h b/db/flush_job.h
index 0534466d2..c504b14fd 100644
--- a/db/flush_job.h
+++ b/db/flush_job.h
@@ -67,6 +67,9 @@ class FlushJob {
   Status Run(uint64_t* file_number = nullptr);
 
  private:
+  void ReportStartedFlush();
+  void ReportFlushInputSize(const autovector<MemTable*>& mems);
+  void RecordFlushIOStats();
   Status WriteLevel0Table(const autovector<MemTable*>& mems, VersionEdit* edit,
                           uint64_t* filenumber);
   const std::string& dbname_;
diff --git a/include/rocksdb/thread_status.h b/include/rocksdb/thread_status.h
index e642284d4..4f67441b5 100644
--- a/include/rocksdb/thread_status.h
+++ b/include/rocksdb/thread_status.h
@@ -85,8 +85,7 @@ struct ThreadStatus {
 
   enum FlushPropertyType : int {
     FLUSH_JOB_ID = 0,
-    FLUSH_BYTES_READ,
-    FLUSH_BYTES_REMAIN,
+    FLUSH_BYTES_MEMTABLES,
     FLUSH_BYTES_WRITTEN,
     NUM_FLUSH_PROPERTIES
   };
diff --git a/util/thread_operation.h b/util/thread_operation.h
index 6df304203..709e755a3 100644
--- a/util/thread_operation.h
+++ b/util/thread_operation.h
@@ -107,8 +107,7 @@ static OperationProperty compaction_operation_properties[] = {
 
 static OperationProperty flush_operation_properties[] = {
   {ThreadStatus::FLUSH_JOB_ID, "JobID"},
-  {ThreadStatus::FLUSH_BYTES_READ, "BytesRead"},
-  {ThreadStatus::FLUSH_BYTES_REMAIN, "BytesRemain"},
+  {ThreadStatus::FLUSH_BYTES_MEMTABLES, "BytesMemtables"},
   {ThreadStatus::FLUSH_BYTES_WRITTEN, "BytesWritten"}
 };
 
diff --git a/util/thread_status_impl.cc b/util/thread_status_impl.cc
index 52dff91f2..6c72160b9 100644
--- a/util/thread_status_impl.cc
+++ b/util/thread_status_impl.cc
@@ -18,21 +18,33 @@ const std::string& ThreadStatus::GetThreadTypeName(
     ThreadStatus::ThreadType thread_type) {
   static std::string thread_type_names[NUM_THREAD_TYPES + 1] = {
       "High Pri", "Low Pri", "User", "Unknown"};
+  if (thread_type < 0 || thread_type >= NUM_THREAD_TYPES) {
+    return thread_type_names[NUM_THREAD_TYPES];  // "Unknown"
+  }
   return thread_type_names[thread_type];
 }
 
 const std::string& ThreadStatus::GetOperationName(
     ThreadStatus::OperationType op_type) {
+  if (op_type < 0 || op_type >= NUM_OP_TYPES) {
+    return global_operation_table[OP_UNKNOWN].name;
+  }
   return global_operation_table[op_type].name;
 }
 
 const std::string& ThreadStatus::GetOperationStageName(
     ThreadStatus::OperationStage stage) {
+  if (stage < 0 || stage >= NUM_OP_STAGES) {
+    return global_op_stage_table[STAGE_UNKNOWN].name;
+  }
   return global_op_stage_table[stage].name;
 }
 
 const std::string& ThreadStatus::GetStateName(
     ThreadStatus::StateType state_type) {
+  if (state_type < 0 || state_type >= NUM_STATE_TYPES) {
+    return global_state_table[STATE_UNKNOWN].name;
+  }
   return global_state_table[state_type].name;
 }