Limit number of threads

5 files changed, 132 insertions, 100 deletions

diff --git a/cppbuild.cc b/cppbuild.cc
index d7c0537..77ed1f3 100644
--- a/cppbuild.cc
+++ b/cppbuild.cc
@@ -1,5 +1,6 @@
 #if 0
-if [ "cppbuild" -ot "$0" ]; then
+if [ "cppbuild" -ot "$0" ]
+then
 	echo "Rebuilding cppbuild"
 	g++ -std=c++17 -pthread $0 libcppbuild.a -o cppbuild
 	[ $? != 0 ] && exit 1
diff --git a/libcppbuild.cc b/libcppbuild.cc
index 35eff8f..3cba49f 100644
--- a/libcppbuild.cc
+++ b/libcppbuild.cc
@@ -3,11 +3,18 @@
 #include <filesystem>
 #include <iostream>
 #include <utility>
+#include <list>
+#include <chrono>
+#include <thread>
 
 #include "libcppbuild.h"
 #include "task.h"
 #include "settings.h"
 
+#include <unistd.h>
+
+using namespace std::chrono_literals;
+
 int main(int argc, const char* argv[])
 {
 	Settings settings;
@@ -15,6 +22,9 @@ int main(int argc, const char* argv[])
 	// TODO: Set from commandline
 	settings.builddir = "build/foo";
 
+	settings.parallel_processes =
+		std::max(1u, std::thread::hardware_concurrency() * 3);
+
 	std::filesystem::path builddir(settings.builddir);
 	std::filesystem::create_directories(builddir);
 
@@ -49,16 +59,50 @@ int main(int argc, const char* argv[])
 	}
 
 	std::cout << "Building\n";
+
+	std::list<std::future<int>> processes;
+
 	// Start all tasks
-	for(auto& task : tasks)
+	auto task = tasks.begin();
+	while(task != tasks.end())
 	{
-		task.start();
+		while(processes.size() < settings.parallel_processes &&
+		      task != tasks.end())
+		{
+			processes.emplace_back(
+				std::async(std::launch::async,
+				           [task]()
+				           {
+					           return task->run();
+				           }));
+			++task;
+			std::this_thread::sleep_for(10ms);
+		}
+
+		for(auto process = processes.begin();
+		    process != processes.end();
+		    ++process)
+		{
+			if(process->valid())
+			{
+				if(process->get() != 0)
+				{
+					return 1;
+				}
+				processes.erase(process);
+				break;
+			}
+		}
+
+		std::this_thread::sleep_for(10ms);
 	}
 
-	// Wait for all tasks
-	for(auto& task : tasks)
+	for(auto process = processes.begin();
+	    process != processes.end();
+	    ++process)
 	{
-		if(task.wait() != 0)
+		process->wait();
+		if(process->get() != 0)
 		{
 			return 1;
 		}
diff --git a/settings.h b/settings.h
index 302c6d7..f60a53b 100644
--- a/settings.h
+++ b/settings.h
@@ -1,7 +1,10 @@
 // -*- c++ -*-
 #pragma once
 
+#include <cstddef>
+
 struct Settings
 {
 	std::string builddir;
+	std::size_t parallel_processes;
 };
diff --git a/task.cc b/task.cc
index 4dcbbd8..4728a1c 100644
--- a/task.cc
+++ b/task.cc
@@ -94,96 +94,85 @@ Task::Task(const BuildConfiguration& config, const Settings& settings,
 	depsFile += ".d";
 }
 
-void Task::start()
+int Task::run()
 {
-	future =
-		std::async(std::launch::async,
-		 [&]()
-		 {
-			 if(!std::filesystem::exists(sourceFile))
-			 {
-				 std::cout << "Missing source file: " << std::string(sourceFile) << "\n";
-				 return 1;
-			 }
-
-			 bool recompile{false};
-
-			 if(!recompile &&
-			    !std::filesystem::exists(targetFile))
-			 {
-				 recompile = true;
-				 std::cout << "Missing targetFile\n";
-			 }
-
-			 if(!recompile &&
-			    !std::filesystem::exists(depsFile))
-			 {
-				 recompile = true;
-				 std::cout << "Missing depsFile\n";
-			 }
-
-			 if(!recompile &&
-			    std::filesystem::last_write_time(sourceFile) >
-			    std::filesystem::last_write_time(depsFile))
-			 {
-				 recompile = true;
-				 std::cout << "The sourceFile newer than depsFile\n";
-			 }
-
-			 if(!recompile)
-			 {
-				 auto depList = readDeps(depsFile);
-				 for(const auto& dep : depList)
-				 {
-					 if(!std::filesystem::exists(dep) ||
-					    std::filesystem::last_write_time(targetFile) <
-					    std::filesystem::last_write_time(dep))
-					 {
-						 recompile = true;
-						 std::cout << "The targetFile older than dep\n";
-						 break;
-					 }
-				 }
-			 }
-
-			 if(!recompile &&
-			    std::filesystem::last_write_time(sourceFile) >
-			    std::filesystem::last_write_time(targetFile))
-			 {
-				 recompile = true;
-				 std::cout << "The targetFile older than sourceFile\n";
-			 }
-
-			 if(recompile)
-			 {
-				 std::string comp = "g++";
-				 std::string flags = config.cxxflags;
-				 if(std::string(sourceFile.extension()) == ".c")
-				 {
-					 comp = "gcc";
-					 flags = config.cflags;
-				 }
-				 std::string cmd = comp +
-				 " -MMD -c " + std::string(sourceFile) + " " +
-				 flags + " " +
-				 "-o " + std::string(targetFile);
-				 std::cout << cmd << "\n";
-
-				 if(system(cmd.data()))
-				 {
-					 return 1;
-				 }
-				 return 0;
-			 }
-
-			 return 0;
-		 });
-}
+	if(!std::filesystem::exists(sourceFile))
+	{
+		std::cout << "Missing source file: " << std::string(sourceFile) << "\n";
+		return 1;
+	}
 
-int Task::wait()
-{
-	future.wait();
-	return future.get();
+	bool recompile{false};
+
+	if(!recompile &&
+	   !std::filesystem::exists(targetFile))
+	{
+		recompile = true;
+		//std::cout << "Missing targetFile\n";
+	}
+
+	if(!recompile &&
+	   !std::filesystem::exists(depsFile))
+	{
+		recompile = true;
+		//std::cout << "Missing depsFile\n";
+	}
+
+	if(!recompile &&
+	   std::filesystem::last_write_time(sourceFile) >
+	   std::filesystem::last_write_time(depsFile))
+	{
+		recompile = true;
+		//std::cout << "The sourceFile newer than depsFile\n";
+	}
+
+	if(!recompile)
+	{
+		auto depList = readDeps(depsFile);
+		for(const auto& dep : depList)
+		{
+			if(!std::filesystem::exists(dep) ||
+			   std::filesystem::last_write_time(targetFile) <
+			   std::filesystem::last_write_time(dep))
+			{
+				recompile = true;
+				//std::cout << "The targetFile older than dep\n";
+				break;
+			}
+		}
+	}
+
+	if(!recompile &&
+	   std::filesystem::last_write_time(sourceFile) >
+	   std::filesystem::last_write_time(targetFile))
+	{
+		recompile = true;
+		//std::cout << "The targetFile older than sourceFile\n";
+	}
+
+	if(recompile)
+	{
+		std::string comp = "g++";
+		std::string flags = config.cxxflags;
+		if(std::string(sourceFile.extension()) == ".c")
+		{
+			comp = "gcc";
+			flags = config.cflags;
+		}
+		std::string cmd = comp +
+			" -MMD -c " + std::string(sourceFile) + " " +
+			flags + " " +
+			"-o " + std::string(targetFile);
+		std::cout << cmd << "\n";
+
+		if(system(cmd.data()))
+		{
+			return 1;
+		}
+		return 0;
+	}
+
+	return 0;
 }
 
 int Task::clean()
diff --git a/task.h b/task.h
index ac56e8a..ee67b5c 100644
--- a/task.h
+++ b/task.h
@@ -16,10 +16,7 @@ public:
 	     const Settings& settings,
 	     const std::string& source);
 
-	void start();
-
-	int wait();
-
+	int run();
 	int clean();
 
 	std::vector<std::string> depends();
@@ -28,8 +25,6 @@ public:
 	std::filesystem::path targetFile;
 	std::filesystem::path depsFile;
 
-	std::future<int> future;
-
 	const BuildConfiguration& config;
 	const Settings& settings;
 };