From 0a36c669c6cbac2ffdd1a47543e0fad8532294c8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Nils=20O=2E=20Sel=C3=A5sdal?= <noselasd@fiane.dyndns.org>
Date: Tue, 15 Oct 2013 21:35:10 +0200
Subject: [PATCH] More ratelimit optimizations

---
 include/ucore/rate_limit.h |  4 ++--
 src/rate_limit.c           | 15 ++++++++-------
 2 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/include/ucore/rate_limit.h b/include/ucore/rate_limit.h
index 10bd00f..6e9ff42 100644
--- a/include/ucore/rate_limit.h
+++ b/include/ucore/rate_limit.h
@@ -34,7 +34,7 @@
  *
  * uc_ratelimit_init(&r,20, 1, time(NULL));
  *
- * NOTE. 2 * (period + 1) * tickets * tickets must not exceed the range of the RateLimit.funds
+ * NOTE. (period + 1) * tickets must not exceed the range of the RateLimit.funds
  *
  * for (;;) {
  *    int fd = accept(..);
@@ -67,7 +67,7 @@ struct RateLimit {
  * Initialize a struct RateLimit, which can hand out @tickets per @period
  * the perioid must be in the same units as the current_ts
  * 
- * NOTE. 2 * (period + 1) * tickets * tickets must not exceed the range of the RateLimit.funds
+ * NOTE. 2 * (period + 1) * tickets must not exceed the range of the RateLimit.funds
  *
  * @param r RateLimit to initialize
  * @param tickets number of tickets (bucket depth)
diff --git a/src/rate_limit.c b/src/rate_limit.c
index 2ca92ae..9bb51d0 100644
--- a/src/rate_limit.c
+++ b/src/rate_limit.c
@@ -5,11 +5,7 @@ void uc_ratelimit_init(struct RateLimit *r, long tickets, long period, long curr
 {
     r->tickets = tickets;
 
-    if (tickets > period) {
-        r->ticket_cost = tickets * period;
-    } else {
-        r->ticket_cost = period;
-    }
+    r->ticket_cost = period;
 
     r->period = period;
     r->funds = r->ticket_cost * tickets;
@@ -48,8 +44,13 @@ int uc_ratelimit_allow(struct RateLimit *r, long current_ts)
 
     //Calculate the cost of tickets that became available since 
     //the last time. 
-    r->funds += diff_period  * 
-                            ((r->tickets * r->ticket_cost) / r->period);
+    r->funds += diff_period * r->tickets;
+
+    //the below is the real algorithm, with ticket_cost = 
+    //tickets * period. 
+    //we have optimized this to the expression used above
+    //r->funds += diff_period  * 
+    //                        ((r->tickets * r->ticket_cost) / r->period);
 
     //throttle handing out tickets
     if (r->funds > r->ticket_cost * r->tickets) {