X-Git-Url: http://info.iut-bm.univ-fcomte.fr/pub/gitweb/simgrid.git/blobdiff_plain/87c589b94e563580e8e0585079cdba97914d791d..aa9cfa5743045b941f3afca368462ea2be992a5f:/src/kernel/context/ContextSwapped.cpp

diff --git a/src/kernel/context/ContextSwapped.cpp b/src/kernel/context/ContextSwapped.cpp
index be10ff854b..87da1fcf61 100644
--- a/src/kernel/context/ContextSwapped.cpp
+++ b/src/kernel/context/ContextSwapped.cpp
@@ -34,33 +34,26 @@ namespace simgrid {
 namespace kernel {
 namespace context {
 
-/* Sequential execution */
-unsigned long SwappedContext::process_index_;
-
-/* Parallel execution */
-simgrid::xbt::Parmap<smx_actor_t>* SwappedContext::parmap_;
-std::atomic<uintptr_t> SwappedContext::threads_working_;       /* number of threads that have started their work */
+/* rank of the execution thread */
 thread_local uintptr_t SwappedContext::worker_id_;             /* thread-specific storage for the thread id */
-std::vector<SwappedContext*> SwappedContext::workers_context_; /* space to save the worker's context in each thread */
 
-void SwappedContext::initialize()
+SwappedContextFactory::SwappedContextFactory(std::string name)
+    : ContextFactory(name), parallel_(SIMIX_context_is_parallel())
 {
-  parmap_ = nullptr;
+  parmap_ = nullptr; // will be created lazily with the right parameters if needed (ie, in parallel)
   workers_context_.clear();
-  workers_context_.resize(SIMIX_context_get_nthreads(), nullptr);
+  workers_context_.resize(parallel_ ? SIMIX_context_get_nthreads() : 1, nullptr);
 }
-
-void SwappedContext::finalize()
+SwappedContextFactory::~SwappedContextFactory()
 {
   delete parmap_;
   parmap_ = nullptr;
   workers_context_.clear();
 }
 
-SwappedContext* SwappedContext::maestro_context_ = nullptr;
-
-SwappedContext::SwappedContext(std::function<void()> code, void_pfn_smxprocess_t cleanup_func, smx_actor_t process)
-    : Context(std::move(code), cleanup_func, process)
+SwappedContext::SwappedContext(std::function<void()> code, void_pfn_smxprocess_t cleanup_func, smx_actor_t process,
+                               SwappedContextFactory* factory)
+    : Context(std::move(code), cleanup_func, process), factory_(factory)
 {
   if (has_code()) {
     if (smx_context_guard_size > 0 && not MC_is_active()) {
@@ -115,7 +108,7 @@ SwappedContext::SwappedContext(std::function<void()> code, void_pfn_smxprocess_t
 
 SwappedContext::~SwappedContext()
 {
-  if (stack_ == nullptr)
+  if (stack_ == nullptr) // maestro has no extra stack
     return;
 
 #if HAVE_VALGRIND_H
@@ -141,42 +134,133 @@ SwappedContext::~SwappedContext()
   xbt_free(stack_);
 }
 
-void SwappedContext::suspend()
+void SwappedContext::set_maestro(SwappedContext* ctx)
 {
-  /* determine the next context */
-  SwappedContext* next_context;
-  unsigned long int i = process_index_;
-  process_index_++;
-
-  if (i < simix_global->process_to_run.size()) {
-    /* execute the next process */
-    XBT_DEBUG("Run next process");
-    next_context = static_cast<SwappedContext*>(simix_global->process_to_run[i]->context_);
-  } else {
-    /* all processes were run, return to maestro */
-    XBT_DEBUG("No more process to run");
-    next_context = static_cast<SwappedContext*>(get_maestro());
+  if (factory_->threads_working_ == 0) // Don't save the soul of minions, only the one of maestro
+    factory_->workers_context_[0] = ctx;
+}
+
+void SwappedContext::stop()
+{
+  Context::stop();
+  /* We must cut the actor execution using an exception to properly free the C++ RAII variables */
+  throw StopRequest();
+}
+
+/** Maestro wants to run all ready actors */
+void SwappedContextFactory::run_all()
+{
+  /* This function is called by maestro at the beginning of a scheduling round to get all working threads executing some
+   * stuff It is much easier to understand what happens if you see the working threads as bodies that swap their soul
+   * for the ones of the simulated processes that must run.
+   */
+  if (parallel_) {
+    threads_working_ = 0;
+
+    // We lazily create the parmap so that all options are actually processed when doing so.
+    if (parmap_ == nullptr)
+      parmap_ = new simgrid::xbt::Parmap<smx_actor_t>(SIMIX_context_get_nthreads(), SIMIX_context_get_parallel_mode());
+
+    // Usually, Parmap::apply() executes the provided function on all elements of the array.
+    // Here, the executed function does not return the control to the parmap before all the array is processed:
+    //   - suspend() should switch back to the worker_context (either maestro or one of its minions) to return
+    //     the control to the parmap. Instead, it uses parmap_->next() to steal another work, and does it directly.
+    //     It only yields back to worker_context when the work array is exhausted.
+    //   - So, resume() is only launched from the parmap for the first job of each minion.
+    parmap_->apply(
+        [](smx_actor_t process) {
+          SwappedContext* context = static_cast<SwappedContext*>(process->context_);
+          context->resume();
+        },
+        simix_global->process_to_run);
+  } else { // sequential execution
+    if (simix_global->process_to_run.empty())
+      return;
+
+    /* maestro is already saved in the first slot of workers_context_ */
+    smx_actor_t first_actor = simix_global->process_to_run.front();
+    process_index_          = 1;
+    /* execute the first actor; it will chain to the others when using suspend() */
+    static_cast<SwappedContext*>(first_actor->context_)->resume();
   }
-  Context::set_current(next_context);
-  this->swap_into(next_context);
 }
 
+/** Maestro wants to yield back to a given actor, so awake it on the current thread
+ *
+ * In parallel, it is only applied to the N first elements of the parmap array,
+ * where N is the amount of worker threads in the parmap.
+ * See SwappedContextFactory::run_all for details.
+ */
 void SwappedContext::resume()
 {
-  SwappedContext* old = static_cast<SwappedContext*>(self());
-  Context::set_current(this);
-  old->swap_into(this);
+  if (factory_->parallel_) {
+    // Save the thread number (my body) in an os-thread-specific area
+    worker_id_ = factory_->threads_working_.fetch_add(1, std::memory_order_relaxed);
+    // Save my current soul (either maestro, or one of the minions) in a permanent area
+    SwappedContext* worker_context = static_cast<SwappedContext*>(self());
+    factory_->workers_context_[worker_id_] = worker_context;
+    // Switch my soul and the actor's one
+    Context::set_current(this);
+    worker_context->swap_into(this);
+    // No body runs that soul anymore at this point, but it is stored in a safe place.
+    // When the executed actor will do a blocking action, SIMIX_process_yield() will call suspend(), below.
+  } else { // sequential execution
+    SwappedContext* old = static_cast<SwappedContext*>(self());
+    Context::set_current(this);
+    old->swap_into(this);
+  }
 }
 
-void SwappedContext::run_all()
+/** The actor wants to yield back to maestro, because it is blocked in a simcall (ie in SIMIX_process_yield())
+ *
+ * Actually, it does not really yield back to maestro, but directly into the next executable actor.
+ *
+ * This makes the parmap::apply awkward (see ParallelUContext::run_all()) because it only apply regularly
+ * on the few first elements of the array, but it saves a lot of context switches back to maestro,
+ * and directly forth to the next executable actor.
+ */
+void SwappedContext::suspend()
 {
-  if (simix_global->process_to_run.empty())
-    return;
-  smx_actor_t first_process = simix_global->process_to_run.front();
-  process_index_            = 1;
-  /* execute the first process */
-  static_cast<SwappedContext*>(first_process->context_)->resume();
+  if (factory_->parallel_) {
+    // Get some more work to directly swap into the next executable actor instead of yielding back to the parmap
+    boost::optional<smx_actor_t> next_work = factory_->parmap_->next();
+    SwappedContext* next_context;
+    if (next_work) {
+      // There is a next soul to embody (ie, another executable actor)
+      XBT_DEBUG("Run next process");
+      next_context = static_cast<SwappedContext*>(next_work.get()->context_);
+    } else {
+      // All actors were run, go back to the parmap context
+      XBT_DEBUG("No more actors to run");
+      // worker_id_ is the identity of my body, stored in thread_local when starting the scheduling round
+      next_context = factory_->workers_context_[worker_id_];
+      // When given that soul, the body will wait for the next scheduling round
+    }
+
+    // Get the next soul to run, either from another actor or the initial minion's one
+    Context::set_current(next_context);
+    this->swap_into(next_context);
+
+  } else { // sequential execution
+    /* determine the next context */
+    SwappedContext* next_context;
+    unsigned long int i = factory_->process_index_;
+    factory_->process_index_++;
+
+    if (i < simix_global->process_to_run.size()) {
+      /* Actually swap into the next actor directly without transiting to maestro */
+      XBT_DEBUG("Run next actor");
+      next_context = static_cast<SwappedContext*>(simix_global->process_to_run[i]->context_);
+    } else {
+      /* all processes were run, actually return to maestro */
+      XBT_DEBUG("No more actors to run");
+      next_context = factory_->workers_context_[0];
+    }
+    Context::set_current(next_context);
+    this->swap_into(next_context);
+  }
 }
+
 } // namespace context
 } // namespace kernel
 } // namespace simgrid