Scalable pid allocation

604a888d · Frans Kaashoek · 5a376f5f · 604a888d · 604a888d
--- a/proc.c
+++ b/proc.c
@@ -12,7 +12,6 @@ struct ptable ptables[NCPU];
 struct runq runqs[NCPU];
 static struct proc *initproc;

-int nextpid = 1;
 extern void forkret(void);
 extern void trapret(void);

@@ -23,6 +22,8 @@ pinit(void)
  int i;

  for (c = 0; c < NCPU; c++) {
+    ptables[c].nextpid = 1;
+
    ptables[c].name[0] = (char) (c + '0');
    safestrcpy(ptables[c].name+1, "ptable", MAXNAME-1);
    initlock(&ptables[c].lock, ptables[c].name);
@@ -48,6 +49,7 @@ allocproc(void)
 {
  struct proc *p;
  char *sp;
+  int pid;

  acquire(&ptable->lock);
  for(p = ptable->proc; p < &ptable->proc[NPROC]; p++)
@@ -57,8 +59,9 @@ allocproc(void)
  return 0;

 found:
+  pid = ptable->nextpid++;
  p->state = EMBRYO;
-  p->pid = nextpid++;   // XXX global var!
+  p->pid = (cpu->id & 0xFFFF) << 16 | (pid & 0xFFFF);
  release(&ptable->lock);

  // Allocate kernel stack if possible.

--- a/proc.h
+++ b/proc.h
@@ -72,8 +72,8 @@ struct cpu {
  struct cpu *cpu;
  struct proc *proc;           // The currently-running process.
  struct ptable *ptable;       // The per-core proc table
-  struct kmem *kmem;           // The per-core proc table
-  struct runq *runq;           // The per-core proc table
+  struct kmem *kmem;           // The per-core memory table
+  struct runq *runq;           // The per-core runq
 };

 struct runq {
@@ -87,6 +87,7 @@ struct ptable {
  struct spinlock lock;
  struct proc proc[NPROC];
  struct proc *runq;
+  int nextpid;
 };

 struct condtab {