Merge branch 'scale' of git+ssh://pdos.csail.mit.edu/home/am0/6.828/xv6 into scale

f2b96eaa · Robert Morris · e661e06a · e7260cf3 · f2b96eaa · f2b96eaa
--- a/defs.h
+++ b/defs.h
@@ -115,6 +115,7 @@ void            sched(void);
 void            userinit(void);
 int             wait(void);
 void            yield(void);
+void            migrate(void);
 // swtch.S
 void            swtch(struct context**, struct context*);

--- a/exec.c
+++ b/exec.c
@@ -125,7 +125,8 @@ exec(char *path, char **argv)
  switchuvm(proc);
  vmap_decref(oldvmap);
-  // XXX migrate to another core??
+  migrate();
  return 0;
 bad:

--- a/proc.c
+++ b/proc.c
@@ -11,6 +11,7 @@
 struct ptable ptables[NCPU];
 struct runq runqs[NCPU];
+int idle[NCPU];
 static struct proc *initproc;
 extern void forkret(void);
@@ -23,6 +24,9 @@ pinit(void)
  int i;
  for (c = 0; c < NCPU; c++) {
+    idle[c] = 1;
    ptables[c].nextpid = (c << 16) | (1);
    ptables[c].name[0] = (char) (c + '0');
    safestrcpy(ptables[c].name+1, "ptable", MAXNAME-1);
@@ -402,7 +406,31 @@ wait(void)
  }
 }
-void 
+void
+migrate(void)
+{
+  int c;
+  struct proc *p;
+  for (c = 0; c < NCPU; c++) {
+    if (c == cpunum())
+      continue;
+    if (idle[c]) {    // OK if there is a race
+      cprintf("migrate to %d\n", c);
+      p = proc;
+      p->curcycles = 0;
+      p->cpuid = c;
+      addrun(p);
+      acquire(&p->lock);
+      p->state = RUNNABLE;
+      sched();
+      release(&proc->lock);
+      return;
+    }
+  }
+}
+int
 steal(void)
 {
  int c;
@@ -422,11 +450,12 @@ steal(void)
 	p->curcycles = 0;
 	p->cpuid = cpu->id;
 	addrun(p);
-	return;
+	return 1;
      }
    }
    release(&runqs[c].lock);
  }
+  return 0;
 }
 //PAGEBREAK: 42
@@ -464,6 +493,8 @@ scheduler(void)
 	panic("non-runnable process on runq\n");
      STAILQ_REMOVE(&runq->runq, p, proc, run_next);
+      if (idle[cpu->id])
+	idle[cpu->id] = 0;
      release(&runq->lock);
      // Switch to chosen process.  It is the process's job
@@ -491,7 +522,8 @@ scheduler(void)
    if(p==0) {
      release(&runq->lock);
-      steal();
+      if (!steal())
+	idle[cpu->id] = 1;
    }
  }
 }