diff --git a/trunk/src/app/srs_app_config.cpp b/trunk/src/app/srs_app_config.cpp
index 4e90e955c..c2ff3f989 100644
--- a/trunk/src/app/srs_app_config.cpp
+++ b/trunk/src/app/srs_app_config.cpp
@@ -1570,7 +1570,7 @@ SrsConfDirective* SrsConfig::get_refer_publish(string vhost)
     return conf->get("refer_publish");
 }
 
-int SrsConfig::get_chunk_size(const string &vhost)
+int SrsConfig::get_chunk_size(string vhost)
 {
     SrsConfDirective* conf = get_vhost(vhost);
 
@@ -1751,7 +1751,7 @@ SrsConfDirective* SrsConfig::get_vhost_on_dvr_hss_reap_flv(string vhost)
     return conf->get("on_dvr_hss_reap_flv");
 }
 
-bool SrsConfig::get_bw_check_enabled(const string &vhost)
+bool SrsConfig::get_bw_check_enabled(string vhost)
 {
     SrsConfDirective* conf = get_vhost(vhost);
 
@@ -1772,7 +1772,7 @@ bool SrsConfig::get_bw_check_enabled(const string &vhost)
     return true;
 }
 
-string SrsConfig::get_bw_check_key(const string &vhost)
+string SrsConfig::get_bw_check_key(string vhost)
 {
     SrsConfDirective* conf = get_vhost(vhost);
 
@@ -1793,7 +1793,7 @@ string SrsConfig::get_bw_check_key(const string &vhost)
     return conf->arg0();
 }
 
-int SrsConfig::get_bw_check_interval_ms(const string &vhost)
+int SrsConfig::get_bw_check_interval_ms(string vhost)
 {
     SrsConfDirective* conf = get_vhost(vhost);
 
@@ -1814,7 +1814,7 @@ int SrsConfig::get_bw_check_interval_ms(const string &vhost)
     return ::atof(conf->arg0().c_str()) * 1000;
 }
 
-int SrsConfig::get_bw_check_limit_kbps(const string &vhost)
+int SrsConfig::get_bw_check_limit_kbps(string vhost)
 {
     SrsConfDirective* conf = get_vhost(vhost);
 
diff --git a/trunk/src/app/srs_app_config.hpp b/trunk/src/app/srs_app_config.hpp
index 9033ad519..f0b5f2536 100644
--- a/trunk/src/app/srs_app_config.hpp
+++ b/trunk/src/app/srs_app_config.hpp
@@ -457,25 +457,29 @@ public:
     */
     virtual int                 get_time_jitter(std::string vhost);
     /**
-    * 
+    * get the cache queue length, in seconds.
+    * when exceed the queue length, drop packet util I frame.
     */
     virtual double              get_queue_length(std::string vhost);
     /**
-    * 
+    * get the refer antisuck directive.
+    * each args of directive is a refer config.
+    * when the client refer(pageUrl) not match the refer config,
+    * SRS will reject the connection.
     */
     virtual SrsConfDirective*   get_refer(std::string vhost);
     /**
-    * 
+    * get the play refer, refer for play clients.
     */
     virtual SrsConfDirective*   get_refer_play(std::string vhost);
     /**
-    * 
+    * get the publish refer, refer for publish clients.
     */
     virtual SrsConfDirective*   get_refer_publish(std::string vhost);
     /**
-    * 
+    * get the chunk size of vhost.
     */
-    virtual int                 get_chunk_size(const std::string& vhost);
+    virtual int                 get_chunk_size(std::string vhost);
 // forward section
 public:
     /**
@@ -524,19 +528,19 @@ public:
     /**
     * 
     */
-    virtual bool                get_bw_check_enabled(const std::string& vhost);
+    virtual bool                get_bw_check_enabled(std::string vhost);
     /**
     * 
     */
-    virtual std::string         get_bw_check_key(const std::string& vhost);
+    virtual std::string         get_bw_check_key(std::string vhost);
     /**
     * 
     */
-    virtual int                 get_bw_check_interval_ms(const std::string& vhost);
+    virtual int                 get_bw_check_interval_ms(std::string vhost);
     /**
     * 
     */
-    virtual int                 get_bw_check_limit_kbps(const std::string& vhost);
+    virtual int                 get_bw_check_limit_kbps(std::string vhost);
 // vhost edge section
 public:
     /**