# HG changeset patch
# User Roman Arutyunyan <arut@nginx.com>
# Date 1640358831 -10800
# Node ID 56dec0d4e5b1ac034e5d1aeb98cad9e238ccdf58
# Parent  e72db91621807b0587168dca66898302afd8486a
QUIC: avoid excessive buffer allocations in stream output.

Previously, when a few bytes were send to a QUIC stream by the application, a
4K buffer was allocated for these bytes.  Then a STREAM frame was created and
that entire buffer was used as data for that frame.  The frame with the buffer
were in use up until the frame was acked by client.  Meanwhile, when more
bytes were send to the stream, more buffers were allocated and assigned as
data to newer STREAM frames.  In this scenario most buffer memory is unused.

Now the unused part of the stream output buffer is available for further
stream output while earlier parts of the buffer are waiting to be acked.
This is achieved by splitting the output buffer.

diff --git a/src/event/quic/ngx_event_quic.h b/src/event/quic/ngx_event_quic.h
--- a/src/event/quic/ngx_event_quic.h
+++ b/src/event/quic/ngx_event_quic.h
@@ -63,6 +63,7 @@ struct ngx_quic_stream_s {
     uint64_t                   recv_last;
     uint64_t                   final_size;
     ngx_chain_t               *in;
+    ngx_chain_t               *out;
     ngx_uint_t                 cancelable;  /* unsigned  cancelable:1; */
 };
 
diff --git a/src/event/quic/ngx_event_quic_frames.c b/src/event/quic/ngx_event_quic_frames.c
--- a/src/event/quic/ngx_event_quic_frames.c
+++ b/src/event/quic/ngx_event_quic_frames.c
@@ -482,14 +482,14 @@ done:
 
 ngx_int_t
 ngx_quic_order_bufs(ngx_connection_t *c, ngx_chain_t **out, ngx_chain_t *in,
-    size_t offset)
+    off_t limit, off_t offset)
 {
+    off_t         n;
     u_char       *p;
-    size_t        n;
     ngx_buf_t    *b;
     ngx_chain_t  *cl, *sl;
 
-    while (in) {
+    while (in && limit) {
         cl = *out;
 
         if (cl == NULL) {
@@ -523,8 +523,9 @@ ngx_quic_order_bufs(ngx_connection_t *c,
             continue;
         }
 
-        for (p = b->pos + offset; p != b->last && in; /* void */ ) {
+        for (p = b->pos + offset; p != b->last && in && limit; /* void */ ) {
             n = ngx_min(b->last - p, in->buf->last - in->buf->pos);
+            n = ngx_min(n, limit);
 
             if (b->sync) {
                 ngx_memcpy(p, in->buf->pos, n);
@@ -533,6 +534,7 @@ ngx_quic_order_bufs(ngx_connection_t *c,
             p += n;
             in->buf->pos += n;
             offset += n;
+            limit -= n;
 
             if (in->buf->pos == in->buf->last) {
                 in = in->next;
diff --git a/src/event/quic/ngx_event_quic_frames.h b/src/event/quic/ngx_event_quic_frames.h
--- a/src/event/quic/ngx_event_quic_frames.h
+++ b/src/event/quic/ngx_event_quic_frames.h
@@ -31,7 +31,7 @@ ngx_chain_t *ngx_quic_copy_chain(ngx_con
 void ngx_quic_trim_bufs(ngx_chain_t *in, size_t size);
 void ngx_quic_free_bufs(ngx_connection_t *c, ngx_chain_t *in);
 ngx_int_t ngx_quic_order_bufs(ngx_connection_t *c, ngx_chain_t **out,
-    ngx_chain_t *in, size_t offset);
+    ngx_chain_t *in, off_t limit, off_t offset);
 
 #if (NGX_DEBUG)
 void ngx_quic_log_frame(ngx_log_t *log, ngx_quic_frame_t *f, ngx_uint_t tx);
diff --git a/src/event/quic/ngx_event_quic_ssl.c b/src/event/quic/ngx_event_quic_ssl.c
--- a/src/event/quic/ngx_event_quic_ssl.c
+++ b/src/event/quic/ngx_event_quic_ssl.c
@@ -369,7 +369,7 @@ ngx_quic_handle_crypto_frame(ngx_connect
     }
 
     if (f->offset > ctx->crypto_received) {
-        return ngx_quic_order_bufs(c, &ctx->crypto, frame->data,
+        return ngx_quic_order_bufs(c, &ctx->crypto, frame->data, f->length,
                                    f->offset - ctx->crypto_received);
     }
 
diff --git a/src/event/quic/ngx_event_quic_streams.c b/src/event/quic/ngx_event_quic_streams.c
--- a/src/event/quic/ngx_event_quic_streams.c
+++ b/src/event/quic/ngx_event_quic_streams.c
@@ -838,8 +838,9 @@ static ngx_chain_t *
 ngx_quic_stream_send_chain(ngx_connection_t *c, ngx_chain_t *in, off_t limit)
 {
     size_t                  n, flow;
+    ngx_buf_t              *b;
     ngx_event_t            *wev;
-    ngx_chain_t            *cl;
+    ngx_chain_t            *out, **ll;
     ngx_connection_t       *pc;
     ngx_quic_frame_t       *frame;
     ngx_quic_stream_t      *qs;
@@ -862,18 +863,30 @@ ngx_quic_stream_send_chain(ngx_connectio
 
     n = (limit && (size_t) limit < flow) ? (size_t) limit : flow;
 
-    frame = ngx_quic_alloc_frame(pc);
-    if (frame == NULL) {
+    if (ngx_quic_order_bufs(pc, &qs->out, in, n, 0) != NGX_OK) {
         return NGX_CHAIN_ERROR;
     }
 
-    frame->data = ngx_quic_copy_chain(pc, in, n);
-    if (frame->data == NGX_CHAIN_ERROR) {
-        return NGX_CHAIN_ERROR;
+    n = 0;
+    out = qs->out;
+
+    for (ll = &out; *ll; ll = &(*ll)->next) {
+        b = (*ll)->buf;
+
+        if (b->sync) {
+            /* hole */
+            break;
+        }
+
+        n += b->last - b->pos;
     }
 
-    for (n = 0, cl = frame->data; cl; cl = cl->next) {
-        n += ngx_buf_size(cl->buf);
+    qs->out = *ll;
+    *ll = NULL;
+
+    frame = ngx_quic_alloc_frame(pc);
+    if (frame == NULL) {
+        return NGX_CHAIN_ERROR;
     }
 
     while (in && ngx_buf_size(in->buf) == 0) {
@@ -882,6 +895,7 @@ ngx_quic_stream_send_chain(ngx_connectio
 
     frame->level = ssl_encryption_application;
     frame->type = NGX_QUIC_FT_STREAM;
+    frame->data = out;
     frame->u.stream.off = 1;
     frame->u.stream.len = 1;
     frame->u.stream.fin = 0;
@@ -977,6 +991,7 @@ ngx_quic_stream_cleanup_handler(void *da
 
     ngx_rbtree_delete(&qc->streams.tree, &qs->node);
     ngx_quic_free_bufs(pc, qs->in);
+    ngx_quic_free_bufs(pc, qs->out);
 
     if (qc->closing) {
         /* schedule handler call to continue ngx_quic_close_connection() */
@@ -1098,7 +1113,7 @@ ngx_quic_handle_stream_frame(ngx_connect
         qs->final_size = last;
     }
 
-    if (ngx_quic_order_bufs(c, &qs->in, frame->data,
+    if (ngx_quic_order_bufs(c, &qs->in, frame->data, f->length,
                             f->offset - qs->recv_offset)
         != NGX_OK)
     {