for #405, improve the http flv to 3k. 2.0.170

@@ -718,6 +718,7 @@ The play HTTP FLV benchmark by [SB](https://github.com/simple-rtmp-server/srs-be
 |   2014-05-24  |   2.0.167 |   1.0k(1000)  |   players     |   82%     |   86MB    |   -           |
 |   2014-05-24  |   2.0.168 |   2.3k(2300)  |   players     |   92%     |   276MB   |   [code][p17] |
 |   2014-05-24  |   2.0.169 |   3.0k(3000)  |   players     |   94%     |   188MB   |   [code][p18] |
+|   2014-05-24  |   2.0.170 |   3.0k(3000)  |   players     |   89%     |   96MB    |   [code][p19] |
 
 ### Latency benchmark
 

@@ -66,11 +66,14 @@ SrsHttpResponseWriter::SrsHttpResponseWriter(SrsStSocket* io)
     content_length = -1;
     written = 0;
     header_sent = false;
+    nb_iovss_cache = 0;
+    iovss_cache = NULL;
 }
 
 SrsHttpResponseWriter::~SrsHttpResponseWriter()
 {
     srs_freep(hdr);
+    srs_freep(iovss_cache);
 }
 
 int SrsHttpResponseWriter::final_request()
@@ -173,8 +176,12 @@ int SrsHttpResponseWriter::writev(iovec* iov, int iovcnt, ssize_t* pnwrite)
     
     // send in chunked encoding.
     int nb_iovss = iovcnt * 4;
-    iovec* iovss = new iovec[nb_iovss];
-    SrsAutoFree(iovec, iovss);
+    iovec* iovss = iovss_cache;
+    if (nb_iovss_cache < nb_iovss) {
+        srs_freep(iovss_cache);
+        nb_iovss_cache = nb_iovss;
+        iovss = iovss_cache = new iovec[nb_iovss];
+    }
     
     char* pheader_cache = header_cache;
     for (int i = 0; i < iovcnt; i++) {

@@ -85,7 +85,10 @@ class SrsHttpResponseWriter : public ISrsHttpResponseWriter
 private:
     SrsStSocket* skt;
     SrsHttpHeader* hdr;
+private:
     char header_cache[SRS_HTTP_HEADER_CACHE_SIZE];
+    iovec* iovss_cache;
+    int nb_iovss_cache;
 private:
     // reply header has been (logically) written
     bool header_wrote;

@@ -31,7 +31,7 @@ CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 // current release version
 #define VERSION_MAJOR       2
 #define VERSION_MINOR       0
-#define VERSION_REVISION    169
+#define VERSION_REVISION    170
 
 // server info.
 #define RTMP_SIG_SRS_KEY "SRS"