/PhotonLibOS

Write fast and agile C++ programs with Photon!

Primary LanguageC++Apache License 2.0Apache-2.0

Photon

CI

Photon is a high-efficiency LibOS framework, based on a set of carefully selected C++ libs.

The role of LibOS is to connect user apps and the OS. Following the principle of Least Astonishment, we designed Photon's API to be as consistent as possible with C++ std and POSIX semantics. This flattens the learning curve for lib users and brings convenience when migrating legacy codebases.

Photon's runtime is driven by a coroutine lib. Out tests show that it has the best I/O performance in the open source world by the year of 2022, even among different programing languages.

As to the project vision, we hope that Photon would help programs run as fast and agile as the photon particle, which exactly is the naming came from.

What's New

  • Version 0.5 is released. Except for various performance improvements, including spinlock, context switch, and new run queue for coroutine scheduling, we have re-implemented the HTTP module so that there is no boost dependency anymore.
  • How to transform RocksDB from multi-threads to coroutines with the help of Photon? Here is the article, en / 中文.
More history...

  • Version 0.4 has come, bringing us these three major features:
    1. Support coroutine local variables. Similar to the C++11 thread_local keyword. See doc.
    2. Support running on macOS platform, both Intel x86_64 and Apple M1 included.
    3. Support LLVM Clang/Apple Clang/GCC compilers.
  • Photon 0.3 was released on 2 Sep 2022. Except for bug fixes and improvements, a new photon::std namespace is added. Developers can search for std::thread, std::mutex in their own projects, and replace them all into the equivalents of photon::std::<xxx>. It's a quick way to transform thread-based programs to coroutine-based ones.
  • Photon 0.2 was released on 28 Jul 2022. This release was mainly focused on network socket, security context and multi-vcpu support. We re-worked the WorkPool so it's more friendly now to write multi-vcpu programs.
  • Made the first tag on 27 Jul 2022. Fix the compatibility for ARM CPU. Throughly compared the TCP echo server performance with other libs.

Features

  • Coroutine library (support multi-core)
  • Async event engine, natively integrated into coroutine scheduling (support epoll or io_uring)
  • Multiple I/O wrappers: psync, posix_aio, libaio, io_uring
  • Multiple socket implementations: tcp (level-trigger/edge-trigger), unix-domain, zero-copy, libcurl, TLS support, etc.
  • A high performance and lightweight RPC client/server
  • A HTTP client/server (even faster than Nginx)
  • A POSIX-like filesystem abstraction and some implementations: local fs, http fs, fuse fs, etc.
  • A bunch of useful tools: io-vector manipulation, resource pool, object cache, mem allocator, callback delegator, pre-compiled logging, lockless ring buffer, etc.

While Photon has already encapsulated many mature OS functionalities, it remains keen to the latest kernel features, and prepared to wrap them into the framework. It is a real killer in the low level programing field.

Performance

1. IO

Compare Photon with fio when reading an 3.5TB NVMe raw device.

IO Engine IO Type IO Size IO Depth DirectIO QPS Throughput CPU util
Photon io_uring Rand-read 4KB 128 Yes 433K 1.73GB 100%
Photon libaio Rand-read 4KB 128 Yes 346K 1.38GB 100%
fio libaio Rand-read 4KB 128 Yes 279K 1.11GB 100%

Note that fio only enables 1 job (process).

Conclusion: Photon is faster than fio under this circumstance.

2. Network

2.1 TCP

Compare Photon with other libs / languages in regard to TCP echo server performance, in descending order.

Client Mode: Streaming

Language Concurrency Model Buffer Size Conn Num QPS Bandwidth CPU util
Photon C++ Stackful Coroutine 512 Bytes 4 1604K 6.12Gb 99%
cocoyaxi C++ Stackful Coroutine 512 Bytes 4 1545K 5.89Gb 99%
tokio Rust Stackless Coroutine 512 Bytes 4 1384K 5.28Gb 98%
acl/lib_fiber C++ Stackful Coroutine 512 Bytes 4 1240K 4.73Gb 94%
Go Golang Stackful Coroutine 512 Bytes 4 1083K 4.13Gb 100%
libgo C++ Stackful Coroutine 512 Bytes 4 770K 2.94Gb 99%
boost::asio C++ Async Callback 512 Bytes 4 634K 2.42Gb 97%
libco C++ Stackful Coroutine 512 Bytes 4 432K 1.65Gb 96%
zab C++20 Stackless Coroutine 512 Bytes 4 412K 1.57Gb 99%
asyncio C++20 Stackless Coroutine 512 Bytes 4 163K 0.60Gb 98%

Client Mode: Ping-pong

Language Concurrency Model Buffer Size Conn Num QPS Bandwidth CPU util
Photon C++ Stackful Coroutine 512 Bytes 1000 412K 1.57Gb 100%
boost::asio C++ Async Callback 512 Bytes 1000 393K 1.49Gb 100%
evpp C++ Async Callback 512 Bytes 1000 378K 1.44Gb 100%
tokio Rust Stackless Coroutine 512 Bytes 1000 365K 1.39Gb 100%
Go Golang Stackful Coroutine 512 Bytes 1000 331K 1.26Gb 100%
acl/lib_fiber C++ Stackful Coroutine 512 Bytes 1000 327K 1.25Gb 100%
swoole PHP Stackful Coroutine 512 Bytes 1000 325K 1.24Gb 99%
zab C++20 Stackless Coroutine 512 Bytes 1000 317K 1.21Gb 100%
cocoyaxi C++ Stackful Coroutine 512 Bytes 1000 279K 1.06Gb 98%
libco C++ Stackful Coroutine 512 Bytes 1000 260K 0.99Gb 96%
libgo C++ Stackful Coroutine 512 Bytes 1000 258K 0.98Gb 156%
TypeScript nodejs Async Callback 512 Bytes 1000 192K 0.75Gb 100%
asyncio C++20 Stackless Coroutine 512 Bytes 1000 142K 0.54Gb 99%
More details...

  • The Streaming client is to measure echo server performance when handling high throughput. A similar scenario in the real world is the multiplexing technology used by RPC and HTTP 2.0. We will set up 4 client processes, and each of them will create only one connection. Send coroutine and recv coroutine are running their loops separately.
  • The Ping-pong client is to measure echo server performance when handling large amounts of connections. We will set up 10 client processes, and each of them will create 100 connections. For a single connection, it has to send first, then receive.
  • Server and client are all cloud VMs, 64Core 128GB, Intel Platinum CPU 2.70GHz. Kernel version is 6.0.7. The network bandwidth (unilateral) is 32Gb.
  • This test was only meant to compare per-core QPS, so we limited the thread number to 1, for instance, set GOMAXPROCS=1.
  • Some libs didn't provide an easy way to configure the number of bytes we would receive in server, which was required by the Streaming test. So we only had their Ping-pong tests run.

Conclusion: Photon socket has the best per-core QPS.

2.2 HTTP

Compare Photon and Nginx when serving static files, using Apache Bench(ab) as client.

File Size QPS CPU util
Photon 4KB 114K 100%
Nginx 4KB 97K 100%

Note that Nginx only enables 1 worker (process).

Conclusion: Photon is faster than Nginx under this circumstance.

Example

See the simple example about how to write a Photon program.

See the full test code of echo server. It also illustrates how to enable multi-core.

Build

1. Install dependencies

CentOS 8.5

dnf install gcc-c++ epel-release cmake
dnf install openssl-devel libcurl-devel libaio-devel

Ubuntu 20.04

apt install cmake
apt install libssl-dev libcurl4-openssl-dev libaio-dev

macOS

brew install cmake openssl

2. Build from source

cd PhotonLibOS
cmake -B build    # On macOS, we need to add -DOPENSSL_ROOT_DIR=/path/to/openssl/
cmake --build build -j

All the libs and executables will be saved in build/output.

3. Examples / Testing

Note the examples and test code are built together. When running performance test, remember to switch to Release build type.

# CentOS 8.5
dnf config-manager --set-enabled PowerTools
dnf install gtest-devel gmock-devel gflags-devel fuse-devel libgsasl-devel
# Ubuntu 20.04
apt install libgtest-dev libgmock-dev libgflags-dev libfuse-dev libgsasl7-dev
# macOS
brew install gflags googletest gsasl

cd PhotonLibOS
cmake -B build -D BUILD_TESTING=1 -D ENABLE_SASL=1 -D ENABLE_FUSE=1 -D ENABLE_URING=1 -D CMAKE_BUILD_TYPE=Debug
cmake --build build -j

cd build
ctest

4. Integration

We recommend using CMake's FetchContent to integrate Photon into your existing project. See this example.

About Photon

Photon was originally created from the storage team of Alibaba Cloud since 2017. It's a production ready library, and has been deployed to hundreds of thousands of hosts as the infrastructure of cloud software. We would like to make a commitment that Photon will be continuously updated, as long as those cloud software still evolve.

Some open source projects are using Photon as well, for instance:

  • containerd/overlaybd The storage backend of accelerated container image, providing a layering block-level image format, designed for container, secure container and virtual machine.
  • data-accelerator/photon-libtcmu A TCMU implementation, reworked from tcmu-runner, acting as a iSCSI target.

Any addition to this list is appreciated, if you have been using Photon, or just enlightened by its coroutine design.

Future work

We are building an independent website for developers to view the documents. Please stay tuned.