http_logger_optimization.diff

1) Soft advance to reduce the number of memmove() calls.

2) Fully buffered stdio, reduce the number of write() syscalls.

diff --git a/http_logger_old.c b/http_logger.c
index 7d75a0ee5a2f..6ab4affb1ee2 100644
--- a/http_logger_old.c
+++ b/http_logger.c
@@ -1687,6 +1687,7 @@ struct buf {
 	uint64_t	cap;
 	uint64_t	len;
 	char		*buf;
+	char		*orig_buf;
 };
 
 struct http_res {
@@ -1783,8 +1784,53 @@ static void http_req_free_all(struct http_req *req)
 	}
 }
 
+static void buf_free(struct buf *b)
+{
+	if (!b->orig_buf)
+		return;
+
+	free(b->orig_buf);
+	b->orig_buf = b->buf = NULL;
+	b->cap = 0;
+	b->len = 0;
+}
+
+static void buf_sync(struct buf *b)
+{
+	if (b->buf == b->orig_buf)
+		return;
+
+	if (!b->len) {
+		buf_free(b);
+		return;
+	}
+
+	memmove(b->orig_buf, b->buf, b->len);
+	b->buf = b->orig_buf;
+}
+
+__attribute__((__unused__))
+static void buf_advance(struct buf *b, size_t len)
+{
+	if (len >= b->len) {
+		buf_free(b);
+		return;
+	}
+
+	b->len -= len;
+	memmove(b->buf, &b->buf[len], b->len);
+}
+
+static void buf_soft_advance(struct buf *b, size_t len)
+{
+	b->buf += len;
+	b->len -= len;
+}
+
 static int buf_append(struct buf *b, const char *data, size_t len)
 {
+	buf_sync(b);
+
 	if (b->len + len > b->cap) {
 		size_t new_cap = b->cap ? b->cap * 2 : 1024;
 		char *new_buf;
@@ -1796,7 +1842,7 @@ static int buf_append(struct buf *b, const char *data, size_t len)
 		if (!new_buf)
 			return -ENOMEM;
 
-		b->buf = new_buf;
+		b->orig_buf = b->buf = new_buf;
 		b->cap = new_cap;
 	}
 
@@ -1805,28 +1851,6 @@ static int buf_append(struct buf *b, const char *data, size_t len)
 	return 0;
 }
 
-static void buf_free(struct buf *b)
-{
-	if (!b->buf)
-		return;
-
-	free(b->buf);
-	b->buf = NULL;
-	b->cap = 0;
-	b->len = 0;
-}
-
-static void buf_advance(struct buf *b, size_t len)
-{
-	if (len >= b->len) {
-		buf_free(b);
-		return;
-	}
-
-	b->len -= len;
-	memmove(b->buf, &b->buf[len], b->len);
-}
-
 static int sock_slots_init(struct sock_slots *ss)
 {
 	int r;
@@ -1992,6 +2016,8 @@ out:
 	return sk;
 }
 
+static char io_buf[8*1024*1024]; // 8 MiB buffer.
+
 static int init_tracer(void)
 {
 	static bool initialized = false;
@@ -2027,7 +2053,7 @@ static int init_tracer(void)
 		goto out;
 	}
 
-	setvbuf(tctx.log_file, NULL, _IOLBF, 0);
+	setvbuf(tctx.log_file, io_buf, _IOFBF, sizeof(io_buf));
 	r = 0;
 out:
 	pthread_mutex_unlock(&x_init_lock);
@@ -2135,10 +2161,10 @@ static int consume_body(struct gwnet_http_body_pctx *c, struct buf *b,
 		c->max_len = MAX_BODY_SIZE;
 		r = gwnet_http_body_parse_chunked(c, NULL, 0);
 		if (c->off)
-			buf_advance(b, c->off);
+			buf_soft_advance(b, c->off);
 	} else {
 		uint64_t sub = min_st(*con_len, b->len);
-		buf_advance(b, sub);
+		buf_soft_advance(b, sub);
 		*con_len -= sub;
 		r = (*con_len == 0) ? 0 : -EAGAIN;
 	}
@@ -2161,7 +2187,7 @@ static int handle_tx_hdr(struct sock *sk)
 	p->max_len = MAX_HEADER_SIZE;
 	r = gwnet_http_req_hdr_parse(p, &req->hdr);
 	if (p->off)
-		buf_advance(b, p->off);
+		buf_soft_advance(b, p->off);
 	if (r)
 		return r;
 	req->con_len = probe_body_len(ff, &req->is_chunked, &inv);
@@ -2200,7 +2226,7 @@ static int handle_rx_hdr(struct sock *sk)
 	p->max_len = MAX_HEADER_SIZE;
 	r = gwnet_http_res_hdr_parse(p, &res->hdr);
 	if (p->off)
-		buf_advance(b, p->off);
+		buf_soft_advance(b, p->off);
 	if (r < 0)
 		return r;
 	res->con_len = probe_body_len(ff, &res->is_chunked, &inv);
@@ -2415,6 +2441,8 @@ static void trace_recv(int fd, const void *buf, size_t len)
 	if (r && r != -EAGAIN)
 		goto out_del;
 
+	fflush(tctx.log_file);
+	buf_sync(&sk->rx_buf);
 	return;
 
 out_del:
@@ -2441,6 +2469,8 @@ static void trace_send(int fd, const void *buf, size_t len)
 	if (r && r != -EAGAIN)
 		goto out_del;
 
+	fflush(tctx.log_file);
+	buf_sync(&sk->tx_buf);
 	sock_put(&tctx.ss, sk);
 	return;