Adding upstream version 18.2.2.upstream/18.2.2

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 23 insertions, 0 deletions

diff --git a/src/rocksdb/monitoring/file_read_sample.h b/src/rocksdb/monitoring/file_read_sample.h
new file mode 100644
index 000000000..82a933e0a
--- /dev/null
+++ b/src/rocksdb/monitoring/file_read_sample.h
@@ -0,0 +1,23 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+#pragma once
+#include "db/version_edit.h"
+#include "util/random.h"
+
+namespace ROCKSDB_NAMESPACE {
+static const uint32_t kFileReadSampleRate = 1024;
+extern bool should_sample_file_read();
+extern void sample_file_read_inc(FileMetaData*);
+
+inline bool should_sample_file_read() {
+  return (Random::GetTLSInstance()->Next() % kFileReadSampleRate == 307);
+}
+
+inline void sample_file_read_inc(FileMetaData* meta) {
+  meta->stats.num_reads_sampled.fetch_add(kFileReadSampleRate,
+                                          std::memory_order_relaxed);
+}
+}  // namespace ROCKSDB_NAMESPACE