From: Marek Vavruša <mvavrusa@cloudflare.com>
Date: Thu, 23 Aug 2018 00:37:01 +0000 (-0700)
Subject: lib/defines: added configurable SRTT limits and lowered probing rate
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=12a06550f69a3cafa352467d401e3de932c2053a;p=thirdparty%2Fknot-resolver.git

lib/defines: added configurable SRTT limits and lowered probing rate

This adds configurable SRTT limits for various network environments.
The probing rate is reduced from 10% to 1%, so that badly connected
nameservers are not selected as often. This is apparent on zone cuts
with a lot of nameservers, e.g. .com. With the probing rate set to
1% the average response time for 300 queries is almost 50% better:
---

diff --git a/lib/defines.h b/lib/defines.h
index b16d0db49..79261a440 100644
--- a/lib/defines.h
+++ b/lib/defines.h
@@ -68,6 +68,12 @@ static inline int KR_COLD kr_error(int x) {
 #ifndef KR_QUERY_NSRETRY_LIMIT
 #define KR_QUERY_NSRETRY_LIMIT 4 /* Maximum number of retries per query. */
 #endif
+#ifndef KR_MIN_NSRTT
+#define KR_MIN_NSRTT 5 /* Minimum NS SRTT cap. */
+#endif
+#ifndef KR_DEFAULT_NSRTT
+#define KR_DEFAULT_NSRTT 250 /* Default/unknown NS SRTT value. */
+#endif
 
 /*
  * Defines.
diff --git a/lib/nsrep.c b/lib/nsrep.c
index 4153f8b77..55ed33873 100644
--- a/lib/nsrep.c
+++ b/lib/nsrep.c
@@ -256,9 +256,9 @@ static int eval_nsrep(const knot_dname_t *owner, const pack_t *addr_set, struct
 	   (score < KR_NS_LONG  || qry->flags.NO_THROTTLE)) {
 		update_nsrep_set(ns, owner, addr_choice, score);
 		ns->reputation = reputation;
-	} else if ((kr_rand_uint(100) < 10) &&
+	} else if ((kr_rand_uint(100) < 1) &&
 		   (kr_rand_uint(KR_NS_MAX_SCORE) >= score)) {
-		/* With 10% chance probe server with a probability
+		/* With 1% chance probe server with a probability
 		 * given by its RTT / MAX_RTT. */
 		update_nsrep_set(ns, owner, addr_choice, score);
 		ns->reputation = reputation;
diff --git a/lib/nsrep.h b/lib/nsrep.h
index 67cff4ad7..feb4de8cf 100644
--- a/lib/nsrep.h
+++ b/lib/nsrep.h
@@ -34,9 +34,9 @@ enum kr_ns_score {
 	KR_NS_MAX_SCORE = KR_CONN_RTT_MAX,
 	KR_NS_TIMEOUT   = (95 * KR_NS_MAX_SCORE) / 100,
 	KR_NS_LONG      = (3 * KR_NS_TIMEOUT) / 4,
-	KR_NS_UNKNOWN   = KR_NS_TIMEOUT / 2,
+	KR_NS_UNKNOWN   = KR_DEFAULT_NSRTT,
 	KR_NS_PENALTY   = 100,
-	KR_NS_GLUED     = 10
+	KR_NS_GLUED     = KR_MIN_NSRTT,
 };
 
 /**