[nginx] SPDY: avoid creating flush frames.

[Valentin Bartenev]

details:   http://hg.nginx.org/nginx/rev/b948f9c73111
branches:  
changeset: 5644:b948f9c73111
user:      Valentin Bartenev <vbart at nginx.com>
date:      Mon Apr 07 23:35:33 2014 +0400
description:
SPDY: avoid creating flush frames.

Previously, an empty frame object was created for an output chain that contains
only sync or flush empty buffers.  But since 39d7eef2e332 every DATA frame has
the flush flag set on its last buffer, so there's no need any more in additional
flush buffers in the output queue and they can be skipped.

Note that such flush frames caused an incorrect $body_bytes_sent value.

diffstat:

 src/http/ngx_http_spdy_filter_module.c |  79 ++++++++++++++++++---------------
 1 files changed, 44 insertions(+), 35 deletions(-)

diffs (112 lines):

diff -r 436f3605195a -r b948f9c73111 src/http/ngx_http_spdy_filter_module.c
--- a/src/http/ngx_http_spdy_filter_module.c	Mon Apr 07 19:27:56 2014 +0400
+++ b/src/http/ngx_http_spdy_filter_module.c	Mon Apr 07 23:35:33 2014 +0400
@@ -625,6 +625,20 @@ ngx_http_spdy_send_chain(ngx_connection_
     r = fc->data;
     stream = r->spdy_stream;
 
+#if (NGX_SUPPRESS_WARN)
+    size = 0;
+#endif
+
+    while (in) {
+        size = ngx_buf_size(in->buf);
+
+        if (size || in->buf->last_buf) {
+            break;
+        }
+
+        in = in->next;
+    }
+
     if (in == NULL) {
 
         if (stream->queued) {
@@ -638,8 +652,6 @@ ngx_http_spdy_send_chain(ngx_connection_
 
     sc = stream->connection;
 
-    size = ngx_buf_size(in->buf);
-
     if (size && ngx_http_spdy_flow_control(sc, stream) == NGX_DECLINED) {
         fc->write->delayed = 1;
         return in;
@@ -850,48 +862,45 @@ ngx_http_spdy_filter_get_data_frame(ngx_
                    "spdy:%ui create DATA frame %p: len:%uz flags:%ui",
                    stream->id, frame, len, flags);
 
-    if (len || flags) {
+    cl = ngx_chain_get_free_buf(stream->request->pool,
+                                &stream->free_data_headers);
+    if (cl == NULL) {
+        return NULL;
+    }
 
-        cl = ngx_chain_get_free_buf(stream->request->pool,
-                                    &stream->free_data_headers);
-        if (cl == NULL) {
+    buf = cl->buf;
+
+    if (buf->start) {
+        p = buf->start;
+        buf->pos = p;
+
+        p += NGX_SPDY_SID_SIZE;
+
+        (void) ngx_spdy_frame_write_flags_and_len(p, flags, len);
+
+    } else {
+        p = ngx_palloc(stream->request->pool, NGX_SPDY_FRAME_HEADER_SIZE);
+        if (p == NULL) {
             return NULL;
         }
 
-        buf = cl->buf;
+        buf->pos = p;
+        buf->start = p;
 
-        if (buf->start) {
-            p = buf->start;
-            buf->pos = p;
+        p = ngx_spdy_frame_write_sid(p, stream->id);
+        p = ngx_spdy_frame_write_flags_and_len(p, flags, len);
 
-            p += NGX_SPDY_SID_SIZE;
+        buf->last = p;
+        buf->end = p;
 
-            (void) ngx_spdy_frame_write_flags_and_len(p, flags, len);
+        buf->tag = (ngx_buf_tag_t) &ngx_http_spdy_filter_get_data_frame;
+        buf->memory = 1;
+    }
 
-        } else {
-            p = ngx_palloc(stream->request->pool, NGX_SPDY_FRAME_HEADER_SIZE);
-            if (p == NULL) {
-                return NULL;
-            }
+    cl->next = first;
+    first = cl;
 
-            buf->pos = p;
-            buf->start = p;
-
-            p = ngx_spdy_frame_write_sid(p, stream->id);
-            p = ngx_spdy_frame_write_flags_and_len(p, flags, len);
-
-            buf->last = p;
-            buf->end = p;
-
-            buf->tag = (ngx_buf_tag_t) &ngx_http_spdy_filter_get_data_frame;
-            buf->memory = 1;
-        }
-
-        cl->next = first;
-        first = cl;
-
-        last->buf->flush = 1;
-    }
+    last->buf->flush = 1;
 
     frame->first = first;
     frame->last = last;