On Thread Start Callback


This is a community driven feature following issue Github #476.
This feature provides the ability to limit the Speedb threads to run on specific cores in order to gain performance or better control CPU usage.


Speedb introduces a new capability that allows Speedb users to configure a callback function that will run for each Speedb thread that is being spawned.
Using this callback a user could configure the thread affinity the way the user wants.

How to use it?

An example is also available under: examples/
// This example will pin all Speedb threads to the first core
#include <functional>
#include <iostream>
#include <memory>
#include "rocksdb/db.h"
#include "rocksdb/options.h"
using namespace ROCKSDB_NAMESPACE;
#if defined(OS_WIN)
std::string kDBPath = "C:\\Windows\\TEMP\\speedb_thr_affinity";
std::string kDBPath = "/tmp/speedb_thr_affinity";
int main() {
// Open the storage
DB* db = nullptr;
Options options;
// create the DB if it's not already present
options.create_if_missing = true;
auto f = [](std::thread::native_handle_type thr) {
// callback to pin all Speedb threads to the first core.
#if defined(OS_WIN)
#include "winbase.h"
SetThreadAffinityMask(thr, 0);
#include "pthread.h"
std::cout << "thread spawned, thread_id: " << thr << std::endl;
cpu_set_t cpuset;
CPU_SET(0, &cpuset);
pthread_setaffinity_np(thr, sizeof(cpu_set_t), &cpuset);
options.on_thread_start_callback =
Status s = DB::Open(options, kDBPath, &db);
// append new entry
std::string key = "key_1";
std::string put_value = "Speedb is awesome!";
s = db->Put(WriteOptions(), key, put_value);
// retrieve entry
std::string get_value;
s = db->Get(ReadOptions(), key, &get_value);
assert(get_value == put_value);
std::cout << get_value << std::endl;
// close DB
s = db->Close();
return 0;