From 7d3814e5b980e4b49bbdf757ddaca13f9c6f6691 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ren=C3=A9=20Canna=C3=B2?= <rene.cannao@gmail.com>
Date: Sat, 10 Sep 2016 00:02:14 +0000
Subject: [PATCH] Scalability improvements #644

Some minor yet important tweak to spinloop
Replaced rand() with fastrand()
---
 include/gen_utils.h              | 9 +++++++++
 include/proxysql_atomic.h        | 4 ++--
 include/proxysql_structs.h       | 4 ++++
 lib/MySQL_HostGroups_Manager.cpp | 6 ++++--
 4 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/include/gen_utils.h b/include/gen_utils.h
index f28b2bd0b..17c641296 100644
--- a/include/gen_utils.h
+++ b/include/gen_utils.h
@@ -22,6 +22,15 @@ struct _PtrSize_t {
 }; 
 */
 
+#ifndef def_fastrand
+inline int fastrand() {
+	g_seed = (214013*g_seed+2531011);
+	//return (g_seed>>16)&0x7FFF;
+	return (g_seed>>16);
+}
+#define def_fastrand
+#endif
+
 class PtrArray {
 	private:
 	void expand(unsigned int);
diff --git a/include/proxysql_atomic.h b/include/proxysql_atomic.h
index 7d244c0d2..0996d3747 100644
--- a/include/proxysql_atomic.h
+++ b/include/proxysql_atomic.h
@@ -16,9 +16,9 @@ struct _rwlock_t {
 
 /* Pause instruction to prevent excess processor bus usage */
 #define cpu_relax_pa() asm volatile("pause\n": : :"memory")
-#define cpu_relax_us() usleep(10)
+#define cpu_relax_us() usleep(1)
 
-#define RELAX_TRIES	1
+#define RELAX_TRIES	100
 
 static inline unsigned xchg_32(void *ptr, unsigned x) {
     __asm__ __volatile__("xchgl %0,%1"
diff --git a/include/proxysql_structs.h b/include/proxysql_structs.h
index 5e82cd6de..6507b4d1a 100644
--- a/include/proxysql_structs.h
+++ b/include/proxysql_structs.h
@@ -773,6 +773,9 @@ __thread char * mysql_thread___monitor_password;
 #ifdef DEBUG
 __thread bool mysql_thread___session_debug;
 #endif /* DEBUG */
+
+__thread unsigned int g_seed;
+
 #endif /* GLOBAL_DEFINED_HOSTGROUP */
 #else
 extern ProxySQL_GlobalVariables GloVars;
@@ -853,6 +856,7 @@ extern __thread char * mysql_thread___monitor_password;
 #ifdef DEBUG
 extern __thread bool mysql_thread___session_debug;
 #endif /* DEBUG */
+extern __thread unsigned int g_seed;
 #endif /* PROXYSQL_EXTERN */
 
 
diff --git a/lib/MySQL_HostGroups_Manager.cpp b/lib/MySQL_HostGroups_Manager.cpp
index 95929836a..f74bf5052 100644
--- a/lib/MySQL_HostGroups_Manager.cpp
+++ b/lib/MySQL_HostGroups_Manager.cpp
@@ -773,7 +773,8 @@ MySrvC *MyHGC::get_random_MySrvC() {
 			return NULL; // if we reach here, we couldn't find any target
 		}
 
-		unsigned int k=rand()%New_sum;
+		//unsigned int k=rand()%New_sum;
+		unsigned int k=fastrand()%New_sum;
   	k++;
 		New_sum=0;
 
@@ -816,7 +817,8 @@ MySQL_Connection * MySrvConnList::get_random_MyConn() {
 	unsigned int i;
 	unsigned int l=conns->len;
 	if (l) {
-		i=rand()%l;
+		//i=rand()%l;
+		i=fastrand()%l;
 		conn=(MySQL_Connection *)conns->remove_index_fast(i);
 		proxy_debug(PROXY_DEBUG_MYSQL_CONNPOOL, 7, "Returning MySQL Connection %p, server %s:%d\n", conn, conn->parent->address, conn->parent->port);
 		return conn;