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greatly improve the documentation of the parallel execution in simix
authorMartin Quinson <martin.quinson@loria.fr>
Sun, 18 May 2014 17:02:27 +0000 (19:02 +0200)
committerMartin Quinson <martin.quinson@loria.fr>
Sun, 18 May 2014 17:02:49 +0000 (19:02 +0200)
src/simix/smx_context_sysv.c

index cb5b022..c3e5eca 100644 (file)
@@ -244,42 +244,47 @@ static void smx_ctx_sysv_suspend_parallel(smx_context_t context)
 {
 #ifdef CONTEXT_THREADS
   /* determine the next context */
 {
 #ifdef CONTEXT_THREADS
   /* determine the next context */
-  smx_process_t next_work = xbt_parmap_next(sysv_parmap);
+  smx_process_t next_work = xbt_parmap_next(sysv_parmap);  // get the next soul to embody now
   smx_context_t next_context;
   smx_context_t next_context;
-  ucontext_t* next_stack;
+  ucontext_t* next_stack;                                  // will contain the next soul to run, either simulated or initial minion's one
 
 
-  if (next_work != NULL) {
-    /* there is a next process to resume */
+  if (next_work != NULL) {                                 // there is a next soul to embody (ie, a next process to resume)
     XBT_DEBUG("Run next process");
     next_context = next_work->context;
     XBT_DEBUG("Run next process");
     next_context = next_work->context;
-    next_stack = &((smx_ctx_sysv_t) next_context)->uc;
   }
   else {
     /* all processes were run, go to the barrier */
     XBT_DEBUG("No more processes to run");
   }
   else {
     /* all processes were run, go to the barrier */
     XBT_DEBUG("No more processes to run");
-    unsigned long worker_id =
+    unsigned long worker_id =                             // Get back the identity of my body that was stored when starting the scheduling round
         (unsigned long) xbt_os_thread_get_specific(sysv_worker_id_key);
         (unsigned long) xbt_os_thread_get_specific(sysv_worker_id_key);
-    next_context = (smx_context_t)sysv_workers_context[worker_id];
-    next_stack = &((smx_ctx_sysv_t)next_context)->uc;
+    next_context = (smx_context_t)sysv_workers_context[worker_id];  // deduce the initial soul of that body
+                                                                    // When given that soul, the body will wait for the next scheduling round
   }
 
   }
 
+  next_stack = &((smx_ctx_sysv_t)next_context)->uc;
+
   SIMIX_context_set_current(next_context);
   SIMIX_context_set_current(next_context);
-  swapcontext(&((smx_ctx_sysv_t) context)->uc, next_stack);
+  swapcontext(&((smx_ctx_sysv_t) context)->uc, next_stack);  // get that next soul
 #endif
 }
 
 #endif
 }
 
-static void smx_ctx_sysv_resume_parallel(smx_process_t first_process)
+static void smx_ctx_sysv_resume_parallel(smx_process_t simulated_process_to_run)
 {
 #ifdef CONTEXT_THREADS
 {
 #ifdef CONTEXT_THREADS
-  unsigned long worker_id = __sync_fetch_and_add(&sysv_threads_working, 1);
-  xbt_os_thread_set_specific(sysv_worker_id_key, (void*) worker_id);
-  smx_ctx_sysv_t worker_context = (smx_ctx_sysv_t)SIMIX_context_self();
-  sysv_workers_context[worker_id] = worker_context;
-  ucontext_t* worker_stack = &worker_context->uc;
-
-  smx_context_t context = first_process->context;
-  SIMIX_context_set_current(context);
-  swapcontext(worker_stack, &((smx_ctx_sysv_t) context)->uc);
+  unsigned long worker_id = __sync_fetch_and_add(&sysv_threads_working, 1); // what is my containing body?
+  xbt_os_thread_set_specific(sysv_worker_id_key, (void*) worker_id);        // Store the number of my containing body in os-thread-specific area
+  smx_ctx_sysv_t worker_context = (smx_ctx_sysv_t)SIMIX_context_self();     // get my current soul
+  sysv_workers_context[worker_id] = worker_context;                         // write down that this soul is hosted in that body (for now)
+  ucontext_t* worker_stack = &worker_context->uc;                           // retrieves the system-level info that fuels this soul
+
+  smx_context_t context = simulated_process_to_run->context;                // That's the first soul that I should become
+  SIMIX_context_set_current(context);                                       // write in simix that I switched my soul
+  swapcontext(worker_stack, &((smx_ctx_sysv_t) context)->uc);               // actually do that using the relevant syscall
+  // No body runs that soul anymore at this point. Instead the current body took the soul of simulated process
+  // The simulated process wakes back after the call to "SIMIX_context_suspend(self->context);" within smx_process.c::SIMIX_process_yield()
+
+  // From now on, the simulated processes will change their soul with the next soul to execute (in suspend_parallel, above).
+  // When nobody is to be executed in this scheduling round, the last simulated process will take back the initial soul of the current working thread
 #endif
 }
 
 #endif
 }