diff --git a/CHANGES b/CHANGES
index 44461ac4a9..525a6c4498 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,6 @@
+2019.	[tuning]	Reduce the amount of work performed per quantum
+			when cleaning the cache. [RT #15986]
+
 2018.	[bug]		Checking if the HMAC MD5 private file was broken.
 			[RT #15960]
 
diff --git a/lib/dns/cache.c b/lib/dns/cache.c
index 8f1fb11a1e..2019aeaae6 100644
--- a/lib/dns/cache.c
+++ b/lib/dns/cache.c
@@ -15,7 +15,7 @@
  * PERFORMANCE OF THIS SOFTWARE.
  */
 
-/* $Id: cache.c,v 1.69 2006/05/04 02:24:06 marka Exp $ */
+/* $Id: cache.c,v 1.70 2006/05/16 03:54:35 marka Exp $ */
 
 /*! \file */
 
@@ -212,15 +212,16 @@ adjust_increment(cache_cleaner_t *cleaner, unsigned int remaining,
 	}
 
 	new = (names * interval);
-	new /= usecs;
+	new /= (usecs * 2);
 	if (new == 0)
 		new = 1;
-	else if (new > DNS_CACHE_CLEANERINCREMENT)
-		new = DNS_CACHE_CLEANERINCREMENT;
 
 	/* Smooth */
 	new = (new + cleaner->increment * 7) / 8;
 
+	if (new > DNS_CACHE_CLEANERINCREMENT)
+		new = DNS_CACHE_CLEANERINCREMENT;
+
 	cleaner->increment = (unsigned int)new;
 
 	isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE, DNS_LOGMODULE_CACHE,