From 889106af4d8381ac188a6532625e2c642150220f Mon Sep 17 00:00:00 2001
From: Bent Bisballe Nyeng <deva@aasimon.org>
Date: Sat, 12 Jun 2021 15:53:20 +0200
Subject: Limit number of threads

---
 libcppbuild.cc | 54 +++++++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 49 insertions(+), 5 deletions(-)

(limited to 'libcppbuild.cc')

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;
 		}
-- 
cgit v1.2.3