- Rename DPCPU_SUM to DPCPU_VARSUM to better reflect the fact it operates on

member variables of a DPCPU struct.

- Add DPCPU_SUM which sums a DPCPU variable.

Sponsored by:	FreeBSD Foundation
MFC after:	3 days

sys/sys/pcpu.h

@@ -109,7 +109,19 @@ extern uintptr_t dpcpu_off[];
 /*
  * Utility macros.
  */
-#define	DPCPU_SUM(n, var) __extension__					\
+#define	DPCPU_SUM(n) __extension__					\
+({									\
+	u_int _i;							\
+	__typeof(DPCPU_PTR(n)) sum;					\
+									\
+	sum = 0;							\
+	CPU_FOREACH(_i) {						\
+		sum += DPCPU_ID_PTR(_i, n);				\
+	}								\
+	sum;								\
+})
+
+#define	DPCPU_VARSUM(n, var) __extension__				\
 ({									\
 	u_int _i;							\
 	__typeof((DPCPU_PTR(n))->var) sum;				\