Add option cmd option to limit the number of threads

src/PrusaSlicer.cpp

@@ -817,7 +817,13 @@ bool CLI::setup(int argc, char **argv)
         if (opt_loglevel != 0)
             set_logging_level(opt_loglevel->value);
     }
-    
+
+    {
+        const ConfigOptionInt *opt_threads = m_config.opt<ConfigOptionInt>("threads");
+        if (opt_threads != nullptr)
+            thread_count = opt_threads->value;
+    }
+
     //FIXME Validating at this stage most likely does not make sense, as the config is not fully initialized yet.
     std::string validity = m_config.validate();
 

src/libslic3r/PrintConfig.cpp

@@ -5066,6 +5066,11 @@ CLIMiscConfigDef::CLIMiscConfigDef()
     def->label = L("Data directory");
     def->tooltip = L("Load and store settings at the given directory. This is useful for maintaining different profiles or including configurations from a network storage.");
 
+    def = this->add("threads", coInt);
+    def->label = L("Maximum number of threads");
+    def->tooltip = L("Sets the maximum number of threads the slicing process will use. If not defined, slic3r will decide.");
+    def->min = 1;
+
     def = this->add("loglevel", coInt);
     def->label = L("Logging level");
     def->tooltip = L("Sets logging sensitivity. 0:fatal, 1:error, 2:warning, 3:info, 4:debug, 5:trace\n"

src/libslic3r/Thread.cpp

@@ -235,12 +235,11 @@ void name_tbb_thread_pool_threads_set_locale()
 //	const size_t nthreads_hw = std::thread::hardware_concurrency();
 	const size_t nthreads_hw = tbb::this_task_arena::max_concurrency();
 	size_t       nthreads    = nthreads_hw;
+    if (thread_count) {
+        nthreads = std::min(nthreads_hw, *thread_count);
+    }
 
-#if 0
-	// Shiny profiler is not thread safe, thus disable parallelization.
-	disable_multi_threading();
-	nthreads = 1;
-#endif
+    enforce_thread_count(nthreads);
 
 	size_t                  nthreads_running(0);
 	std::condition_variable cv;

src/libslic3r/Utils.hpp

@@ -21,6 +21,7 @@ namespace boost { namespace filesystem { class directory_entry; }}
 
 namespace Slic3r {
 
+inline std::optional<std::size_t> thread_count;
 extern void set_logging_level(unsigned int level);
 extern unsigned get_logging_level();
 // Format memory allocated, separate thousands by comma.
@@ -29,7 +30,7 @@ extern std::string format_memsize_MB(size_t n);
 // The string is non-empty if the loglevel >= info (3) or ignore_loglevel==true.
 // Latter is used to get the memory info from SysInfoDialog.
 extern std::string log_memory_info(bool ignore_loglevel = false);
-extern void disable_multi_threading();
+extern void enforce_thread_count(std::size_t count);
 // Returns the size of physical memory (RAM) in bytes.
 extern size_t total_physical_memory();
 

src/libslic3r/utils.cpp

@@ -123,15 +123,15 @@ unsigned get_logging_level()
     }
 }
 
-void disable_multi_threading()
+void enforce_thread_count(const std::size_t count)
 {
     // Disable parallelization to simplify debugging.
 #ifdef TBB_HAS_GLOBAL_CONTROL
 	{
-		static tbb::global_control gc(tbb::global_control::max_allowed_parallelism, 1);
+		static tbb::global_control gc(tbb::global_control::max_allowed_parallelism, count);
 	}
 #else // TBB_HAS_GLOBAL_CONTROL
-    static tbb::task_scheduler_init *tbb_init = new tbb::task_scheduler_init(1);
+    static tbb::task_scheduler_init *tbb_init = new tbb::task_scheduler_init(count);
     UNUSED(tbb_init);
 #endif // TBB_HAS_GLOBAL_CONTROL
 }