diff --git a/lib/isc/include/isc/mem.h b/lib/isc/include/isc/mem.h
index 2a3ae0a77f..cda2f198f8 100644
--- a/lib/isc/include/isc/mem.h
+++ b/lib/isc/include/isc/mem.h
@@ -15,7 +15,7 @@
  * WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 
-/* $Id: mem.h,v 1.52 2001/06/06 21:02:43 bwelling Exp $ */
+/* $Id: mem.h,v 1.53 2001/06/27 23:29:29 marka Exp $ */
 
 #ifndef ISC_MEM_H
 #define ISC_MEM_H 1
@@ -82,10 +82,14 @@ typedef void (*isc_memfree_t)(void *, void *);
  * _DEBUGRECORD
  *	remember each allocation, and match them up on free.  Crash if
  *	a free doesn't match an allocation
+ * _DEBUGUSAGE
+ *	if a hi_water mark is set print the maximium inuse memory every
+ *	time it is raised once it exceeds the hi_water mark
  */
 extern unsigned int isc_mem_debugging;
 #define ISC_MEM_DEBUGTRACE		0x00000001U
 #define ISC_MEM_DEBUGRECORD		0x00000002U
+#define ISC_MEM_DEBUGUSAGE		0x00000004U
 
 #if ISC_MEM_TRACKLINES
 #define _ISC_MEM_FILELINE	, __FILE__, __LINE__
diff --git a/lib/isc/mem.c b/lib/isc/mem.c
index 813ceec193..a5bb97537b 100644
--- a/lib/isc/mem.c
+++ b/lib/isc/mem.c
@@ -15,7 +15,7 @@
  * WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 
-/* $Id: mem.c,v 1.93 2001/06/11 20:27:16 gson Exp $ */
+/* $Id: mem.c,v 1.94 2001/06/27 23:29:27 marka Exp $ */
 
 #include <config.h>
 
@@ -118,6 +118,7 @@ struct isc_mem {
 	size_t			quota;
 	size_t			total;
 	size_t			inuse;
+	size_t			maxinuse;
 	size_t			hi_water;
 	size_t			lo_water;
 	isc_boolean_t		hi_called;
@@ -700,6 +701,7 @@ isc_mem_createx(size_t init_max_size, size_t target_size,
 	ctx->quota = 0;
 	ctx->total = 0;
 	ctx->inuse = 0;
+	ctx->maxinuse = 0;
 	ctx->hi_water = 0;
 	ctx->lo_water = 0;
 	ctx->hi_called = ISC_FALSE;
@@ -985,6 +987,12 @@ isc__mem_get(isc_mem_t *ctx, size_t size FLARG) {
 		ctx->hi_called = ISC_TRUE;
 		call_water = ISC_TRUE;
 	}
+	if (ctx->inuse > ctx->maxinuse) {
+		ctx->maxinuse = ctx->inuse;
+		if (ctx->hi_water != 0 && ctx->inuse > ctx->hi_water &&
+		    (isc_mem_debugging & ISC_MEM_DEBUGUSAGE) != 0)
+			fprintf(stderr, "maxinuse = %d\n", ctx->inuse);
+	}
 	UNLOCK(&ctx->lock);
 
 	if (call_water) {