uti: Workaround not to share CPU with OpenMP threads

* Assign uti thread to the last idle CPU so that it's not shared with
  an OpenMP thread

Change-Id: Ia42cae056ce81fde9b6dab6286b39a52f3c9e172

arch/arm64/kernel/syscall.c

@@ -58,7 +58,7 @@ static int cpuid_head = 1;
 
 extern int num_processors;
 
-int obtain_clone_cpuid(cpu_set_t *cpu_set) {
+int obtain_clone_cpuid(cpu_set_t *cpu_set, int use_last) {
 	int min_queue_len = -1;
 	int i, min_cpu = -1;
 

arch/x86_64/kernel/syscall.c

@@ -90,11 +90,11 @@ static ptrdiff_t vdso_offset;
 
 extern int num_processors;
 
-int obtain_clone_cpuid(cpu_set_t *cpu_set) {
+int obtain_clone_cpuid(cpu_set_t *cpu_set, int use_last) {
 	int min_queue_len = -1;
-	int cpu, min_cpu = -1;
+	int cpu, min_cpu = -1, uti_cpu = -1;
 	unsigned long irqstate;
-
+	
 	irqstate = ihk_mc_spinlock_lock(&runq_reservation_lock);
 	/* Find the first allowed core with the shortest run queue */
 	for (cpu = 0; cpu < num_processors; ++cpu) {
@@ -109,12 +109,20 @@ int obtain_clone_cpuid(cpu_set_t *cpu_set) {
 			min_queue_len = v->runq_len + v->runq_reserved;
 			min_cpu = cpu;
 		}
-		ihk_mc_spinlock_unlock_noirq(&v->runq_lock);
 
+		/* Record the last tie CPU */
+		if (min_cpu != cpu && v->runq_len + v->runq_reserved == min_queue_len) {
+			uti_cpu = cpu;
+		}
+		dkprintf("%s: cpu=%d,runq_len=%d,runq_reserved=%d,min_cpu=%d,uti_cpu=%d\n", __FUNCTION__, cpu, v->runq_len, v->runq_reserved, min_cpu, uti_cpu);
+		ihk_mc_spinlock_unlock_noirq(&v->runq_lock);
+#if 0
 		if (min_queue_len == 0)
 			break;
+#endif
 	}
 
+	min_cpu = use_last ? uti_cpu : min_cpu;
 	if (min_cpu != -1) {
 		if (get_cpu_local_var(min_cpu)->status != CPU_STATUS_RESERVED)
 			get_cpu_local_var(min_cpu)->status = CPU_STATUS_RESERVED;

executer/include/uprotocol.h

@@ -143,6 +143,7 @@ struct program_load_desc {
 	long stack_premap;
 	unsigned long mpol_bind_mask;
 	int uti_thread_rank; /* N-th clone() spawns a thread on Linux CPU */
+	int uti_use_last_cpu; /* Work-around not to share CPU with OpenMP thread */
 	int nr_processes;
 	int process_rank;
 	char shell_path[SHELL_PATH_MAX_LEN];

executer/user/mcexec.c

@@ -234,6 +234,7 @@ static long stack_max = -1;
 static struct rlimit rlim_stack;
 static char *mpol_bind_nodes = NULL;
 static int uti_thread_rank = 0;
+static int uti_use_last_cpu = 0;
 
 /* Partitioned execution (e.g., for MPI) */
 static int nr_processes = 0;
@@ -1794,6 +1795,12 @@ static struct option mcexec_options[] = {
 		.flag =		NULL,
 		.val =		'u',
 	},
+	{
+		.name =		"uti-use-last-cpu",
+		.has_arg =	no_argument,
+		.flag =		&uti_use_last_cpu,
+		.val =		1,
+	},
 	/* end */
 	{ NULL, 0, NULL, 0, },
 };
@@ -2610,6 +2617,7 @@ int main(int argc, char **argv)
 	}
 
 	desc->uti_thread_rank = uti_thread_rank;
+	desc->uti_use_last_cpu = uti_use_last_cpu;
 
 	/* user_start and user_end are set by this call */
 	if (ioctl(fd, MCEXEC_UP_PREPARE_IMAGE, (unsigned long)desc) != 0) {

kernel/host.c

@@ -506,6 +506,7 @@ static int process_msg_prepare_process(unsigned long rphys)
 	}
 
 	proc->uti_thread_rank = pn->uti_thread_rank;
+	proc->uti_use_last_cpu = pn->uti_use_last_cpu;
 
 #ifdef PROFILE_ENABLE
 	proc->profile = pn->profile;
@@ -612,7 +613,7 @@ static int syscall_packet_handler(struct ihk_ikc_channel_desc *c,
 	case SCD_MSG_SCHEDULE_PROCESS:
 		thread = (struct thread *)packet->arg;
 
-		cpuid = obtain_clone_cpuid(&thread->cpu_set);
+		cpuid = obtain_clone_cpuid(&thread->cpu_set, 0);
 		if (cpuid == -1) {
 			kprintf("No CPU available\n");
 			ret = -1;

kernel/include/process.h

@@ -275,7 +275,7 @@ extern struct list_head	resource_set_list;
 extern mcs_rwlock_lock_t	resource_set_lock;
 extern int idle_halt;
 extern int allow_oversubscribe;
-extern ihk_spinlock_t runq_reservation_lock; /* To serialize runq reservations for competeing fork()s */
+extern ihk_spinlock_t runq_reservation_lock; /* mutex for cpuid reservation (clv->runq_reserved) */
 
 struct process_hash {
 	struct list_head	list[HASH_SIZE];
@@ -557,6 +557,7 @@ struct process {
 	unsigned long heap_extension;
 	unsigned long mpol_bind_mask;
 	int uti_thread_rank; /* Spawn on Linux CPU when clone_count reaches this */
+	int uti_use_last_cpu; /* Work-around not to share CPU with OpenMP thread */
 	int clone_count;
 
 	// perf_event

kernel/include/syscall.h

@@ -201,6 +201,7 @@ struct program_load_desc {
 	long stack_premap;
 	unsigned long mpol_bind_mask;
 	int uti_thread_rank; /* N-th clone() spawns a thread on Linux CPU */
+	int uti_use_last_cpu; /* Work-around not to share CPU with OpenMP thread */
 	int nr_processes;
 	int process_rank;
 	char shell_path[SHELL_PATH_MAX_LEN];
@@ -350,7 +351,7 @@ struct syscall_post {
 #define SYSCALL_FOOTER return do_syscall(&request, ihk_mc_get_processor_id(), 0)
 
 extern long do_syscall(struct syscall_request *req, int cpu, int pid);
-int obtain_clone_cpuid(cpu_set_t *cpu_set);
+int obtain_clone_cpuid(cpu_set_t *cpu_set, int use_last);
 extern long syscall_generic_forwarding(int n, ihk_mc_user_context_t *ctx);
 
 #define DECLARATOR(number,name)		__NR_##name = number,

kernel/syscall.c

@@ -2445,12 +2445,6 @@ unsigned long do_fork(int clone_flags, unsigned long newsp,
         return -EINVAL;
 	}
 
-	cpuid = obtain_clone_cpuid(&old->cpu_set);
-    if (cpuid == -1) {
-		kprintf("do_fork,core not available\n");
-        return -EAGAIN;
-    }
-
 	/* N-th creation put the new on Linux CPU. It's turned off when zero is 
 	   set to uti_thread_rank. */
 	if (oldproc->uti_thread_rank) {
@@ -2463,6 +2457,12 @@ unsigned long do_fork(int clone_flags, unsigned long newsp,
 		}
 	}
 
+	cpuid = obtain_clone_cpuid(&old->cpu_set, old->mod_clone == SPAWN_TO_REMOTE && oldproc->uti_use_last_cpu);
+    if (cpuid == -1) {
+		kprintf("do_fork,core not available\n");
+        return -EAGAIN;
+    }
+
 	new = clone_thread(old, curpc,
 	                    newsp ? newsp : cursp, clone_flags);