This is the C++ QD library, which provides implementations of Queue Delegation (QD) locks for C++11 programs.
It is distributed under the Simplified BSD License. Details can be found in the LICENSE file.
QD locks allow programmers to delegate critical sections to a lock. If the lock is currently free, this will use an efficient lock implementation. However, if the lock is already in use, the critical section will be delegated to the thread currently holding the lock, who becomes the helper. The helper will continue to execute critical sections for other threads until either it finds no more work, or some maximum number of executions has been reached.
This scheme results in drastically higher throughput than with traditional locking algorithms that transfer execution and shared data between threads.
For more details on QD locks see this website.
This library makes use of libnuma, available on linux. For other operating systems support can be turned off, at potential performance costs for NUMA machines. To install libnuma on debian/Ubuntu and derivatives, run
sudo apt-get install libnuma-dev
For gentoo, run
sudo emerge sys-process/numactl
The following compilers are currently supported:
- GCC: g++ versions 4.9 -- 6
- Clang: clang++ versions 3.5 -- 3.8
wget https://github.com/google/googletest/archive/release-1.7.0.tar.gz
tar xzf release-1.7.0.tar.gz
mv googletest-release-1.7.0 tests/gtest-1.7.0
mkdir build
cd build
cmake ../
make -j8
make test
make install
To use this library, include qd.hpp
in your programs.
Here is a minimal example for how to use them:
#include<iostream>
#include<qd.hpp>
int main() {
int counter = 0;
qdlock lock;
std::thread threads[4];
for(auto& t : threads) {
t = std::thread(
[&lock, &counter]() {
lock.delegate_n([&counter]() { counter++; });
}
);
}
for(auto& t : threads) {
t.join();
}
std::cout << "The counter value is " << counter << std::endl;
}
To compile and run a program it may be required to add /usr/local/include/
to your include path and /usr/local/lib
to your library path.
Compiling and running should then work using
g++ -I/usr/local/include/qd/ -L/usr/local/lib/ myprogram.cpp -pthread -lqd -o myprogram
./myprogram
If required, you can adjust some settings in CMake:
cmake -DQD_DEBUG=OFF \
-DQD_TESTS=ON \
-DQD_USE_LIBNUMA=ON \
-DCMAKE_INSTALL_PREFIX=/usr/local \
../
For a library for C code, please see https://github.com/kjellwinblad/qd_lock_lib