rpc-transport/socket: implement read-ahead of RPC headers

This reduces the number of read() system calls on the socket to
complete the full RPC fragment reading.

Change-Id: I421a53af195ead4aad70e09e0172a61ad7912d83
BUG: 821087
Signed-off-by: Anand Avati <avati@redhat.com>
Reviewed-on: http://review.gluster.org/3855
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Jeff Darcy <jdarcy@redhat.com>
Reviewed-by: Amar Tumballi <amarts@redhat.com>

2 files changed, 115 insertions, 7 deletions

diff --git a/rpc/rpc-transport/socket/src/socket.c b/rpc/rpc-transport/socket/src/socket.c
index 97612610975..ae574f5f599 100644
--- a/rpc/rpc-transport/socket/src/socket.c
+++ b/rpc/rpc-transport/socket/src/socket.c
@@ -308,6 +308,112 @@ done:
 	return ret;
 }
 
+
+
+ssize_t
+__socket_ssl_readv (rpc_transport_t *this, struct iovec *opvector, int opcount)
+{
+	socket_private_t    *priv = NULL;
+	int                  sock = -1;
+	int                  ret = -1;
+
+	priv = this->private;
+	sock = priv->sock;
+
+	if (priv->use_ssl) {
+		ret = ssl_read_one (this, opvector->iov_base, opvector->iov_len);
+	} else {
+		ret = readv (sock, opvector, opcount);
+	}
+
+	return ret;
+}
+
+
+ssize_t
+__socket_ssl_read (rpc_transport_t *this, void *buf, size_t count)
+{
+	struct iovec iov = {0, };
+	int          ret = -1;
+
+	iov.iov_base = buf;
+	iov.iov_len = count;
+
+	ret = __socket_ssl_readv (this, &iov, 1);
+
+	return ret;
+}
+
+
+int
+__socket_cached_read (rpc_transport_t *this, struct iovec *opvector, int opcount)
+{
+	socket_private_t   *priv = NULL;
+	int                 sock = -1;
+	struct gf_sock_incoming *in = NULL;
+	int                 req_len = -1;
+	int                 ret = -1;
+
+	priv = this->private;
+	sock = priv->sock;
+	in = &priv->incoming;
+	req_len = iov_length (opvector, opcount);
+
+	if (in->record_state == SP_STATE_READING_FRAGHDR) {
+		in->ra_read = 0;
+		in->ra_served = 0;
+		in->ra_max = 0;
+		in->ra_buf = NULL;
+		goto uncached;
+	}
+
+	if (!in->ra_max) {
+		/* first call after passing SP_STATE_READING_FRAGHDR */
+		in->ra_max = min (RPC_FRAGSIZE (in->fraghdr), GF_SOCKET_RA_MAX);
+		/* Note that the in->iobuf is the primary iobuf into which
+		   headers are read into. By using this itself as our
+		   read-ahead cache, we can avoid memory copies in iov_load
+		*/
+		in->ra_buf = iobuf_ptr (in->iobuf);
+	}
+
+	/* fill read-ahead */
+	if (in->ra_read < in->ra_max) {
+		ret = __socket_ssl_read (this, &in->ra_buf[in->ra_read],
+					 (in->ra_max - in->ra_read));
+		if (ret > 0)
+			in->ra_read += ret;
+
+		/* we proceed to test if there is still cached data to
+		   be served even if readahead could not progress */
+	}
+
+	/* serve cached */
+	if (in->ra_served < in->ra_read) {
+		ret = iov_load (opvector, opcount, &in->ra_buf[in->ra_served],
+				min (req_len, (in->ra_read - in->ra_served)));
+
+		in->ra_served += ret;
+		/* Do not read uncached and cached in the same call */
+		goto out;
+	}
+
+	if (in->ra_read < in->ra_max)
+		/* If there was no cached data to be served, (and we are
+		   guaranteed to have already performed an attempt to progress
+		   readahead above), and we have not yet read out the full
+		   readahead capacity, then bail out for now without doing
+		   the uncached read below (as that will overtake future cached
+		   read)
+		*/
+		goto out;
+uncached:
+	ret = __socket_ssl_readv (this, opvector, opcount);
+out:
+	return ret;
+}
+
+
 /*
  * return value:
  *   0 = success (completed)
@@ -363,13 +469,8 @@ __socket_rwv (rpc_transport_t *this, struct iovec *vector, int count,
                         }
                         this->total_bytes_write += ret;
                 } else {
-			if (priv->use_ssl) {
-				ret = ssl_read_one(this,
-					opvector->iov_base, opvector->iov_len);
-			}
-			else {
-				ret = readv (sock, opvector, opcount);
-			}
+			ret = __socket_cached_read (this, opvector, opcount);
+
 			if (ret == 0) {
 				gf_log(this->name,GF_LOG_DEBUG,"EOF on socket");
 				errno = ENODATA;
diff --git a/rpc/rpc-transport/socket/src/socket.h b/rpc/rpc-transport/socket/src/socket.h
index 2c4b44cf466..78faad9038d 100644
--- a/rpc/rpc-transport/socket/src/socket.h
+++ b/rpc/rpc-transport/socket/src/socket.h
@@ -158,6 +158,8 @@ struct gf_sock_incoming_frag {
         sp_rpcfrag_state_t state;
 };
 
+#define GF_SOCKET_RA_MAX 1024
+
 struct gf_sock_incoming {
         sp_rpcrecord_state_t  record_state;
         struct gf_sock_incoming_frag frag;
@@ -175,6 +177,11 @@ struct gf_sock_incoming {
         char                 complete_record;
         msg_type_t           msg_type;
         size_t               total_bytes_read;
+
+	size_t               ra_read;
+	size_t               ra_max;
+	size_t               ra_served;
+	char                *ra_buf;
 };
 
 typedef struct {