linux/net/tipc/node.h, branch v4.7

tipc: redesign connection-level flow control

2016-05-03T19:51:16Z

There are two flow control mechanisms in TIPC; one at link level that handles network congestion, burst control, and retransmission, and one at connection level which' only remaining task is to prevent overflow in the receiving socket buffer. In TIPC, the latter task has to be solved end-to-end because messages can not be thrown away once they have been accepted and delivered upwards from the link layer, i.e, we can never permit the receive buffer to overflow. Currently, this algorithm is message based. A counter in the receiving socket keeps track of number of consumed messages, and sends a dedicated acknowledge message back to the sender for each 256 consumed message. A counter at the sending end keeps track of the sent, not yet acknowledged messages, and blocks the sender if this number ever reaches 512 unacknowledged messages. When the missing acknowledge arrives, the socket is then woken up for renewed transmission. This works well for keeping the message flow running, as it almost never happens that a sender socket is blocked this way. A problem with the current mechanism is that it potentially is very memory consuming. Since we don't distinguish between small and large messages, we have to dimension the socket receive buffer according to a worst-case of both. I.e., the window size must be chosen large enough to sustain a reasonable throughput even for the smallest messages, while we must still consider a scenario where all messages are of maximum size. Hence, the current fix window size of 512 messages and a maximum message size of 66k results in a receive buffer of 66 MB when truesize(66k) = 131k is taken into account. It is possible to do much better. This commit introduces an algorithm where we instead use 1024-byte blocks as base unit. This unit, always rounded upwards from the actual message size, is used when we advertise windows as well as when we count and acknowledge transmitted data. The advertised window is based on the configured receive buffer size in such a way that even the worst-case truesize/msgsize ratio always is covered. Since the smallest possible message size (from a flow control viewpoint) now is 1024 bytes, we can safely assume this ratio to be less than four, which is the value we are now using. This way, we have been able to reduce the default receive buffer size from 66 MB to 2 MB with maintained performance. In order to keep this solution backwards compatible, we introduce a new capability bit in the discovery protocol, and use this throughout the message sending/reception path to always select the right unit. Acked-by: Ying Xue Signed-off-by: Jon Maloy Signed-off-by: David S. Miller

tipc: propagate peer node capabilities to socket layer

2016-05-03T19:51:15Z

During neighbor discovery, nodes advertise their capabilities as a bit map in a dedicated 16-bit field in the discovery message header. This bit map has so far only be stored in the node structure on the peer nodes, but we now see the need to keep a copy even in the socket structure. This commit adds this functionality. Acked-by: Ying Xue Signed-off-by: Jon Maloy Signed-off-by: David S. Miller

tipc: narrow down interface towards struct tipc_link

2015-11-20T19:06:10Z

We move the definition of struct tipc_link from link.h to link.c in order to minimize its exposure to the rest of the code. When needed, we define new functions to make it possible for external entities to access and set data in the link. Apart from the above, there are no functional changes. Reviewed-by: Ying Xue Signed-off-by: Jon Maloy Signed-off-by: David S. Miller

tipc: narrow down exposure of struct tipc_node

2015-11-20T19:06:10Z

In our effort to have less code and include dependencies between entities such as node, link and bearer, we try to narrow down the exposed interface towards the node as much as possible. In this commit, we move the definition of struct tipc_node, along with many of its associated function declarations, from node.h to node.c. We also move some function definitions from link.c and name_distr.c to node.c, since they access fields in struct tipc_node that should not be externally visible. The moved functions are renamed according to new location, and made static whenever possible. There are no functional changes in this commit. Reviewed-by: Ying Xue Signed-off-by: Jon Maloy Signed-off-by: David S. Miller

tipc: convert node lock to rwlock

2015-11-20T19:06:10Z

According to the node FSM a node in state SELF_UP_PEER_UP cannot change state inside a lock context, except when a TUNNEL_PROTOCOL (SYNCH or FAILOVER) packet arrives. However, the node's individual links may still change state. Since each link now is protected by its own spinlock, we finally have the conditions in place to convert the node spinlock to an rwlock_t. If the node state and arriving packet type are rigth, we can let the link directly receive the packet under protection of its own spinlock and the node lock in read mode. In all other cases we use the node lock in write mode. This enables full concurrent execution between parallel links during steady-state traffic situations, i.e., 99+ % of the time. This commit implements this change. Reviewed-by: Ying Xue Signed-off-by: Jon Maloy Signed-off-by: David S. Miller

tipc: introduce per-link spinlock

2015-11-20T19:06:10Z

As a preparation to allow parallel links to work more independently from each other we introduce a per-link spinlock, to be stored in the struct nodes's link entry area. Since the node lock still is a regular spinlock there is no increase in parallellism at this stage. Reviewed-by: Ying Xue Signed-off-by: Jon Maloy Signed-off-by: David S. Miller

tipc: reduce code dependency between binding table and node layer

2015-11-20T19:06:10Z

The file name_distr.c currently contains three functions, named_cluster_distribute(), tipc_publ_subcscribe() and tipc_publ_unsubscribe() that all directly access fields in struct tipc_node. We want to eliminate such dependencies, so we move those functions to the file node.c and rename them to tipc_node_broadcast(), tipc_node_subscribe() and tipc_node_unsubscribe() respectively. Reviewed-by: Ying Xue Signed-off-by: Jon Maloy Signed-off-by: David S. Miller

tipc: clean up unused code and structures

2015-10-24T13:56:47Z

After the previous changes in this series, we can now remove some unused code and structures, both in the broadcast, link aggregation and link code. There are no functional changes in this commit. Signed-off-by: Jon Maloy Reviewed-by: Ying Xue Signed-off-by: David S. Miller

tipc: let broadcast packet reception use new link receive function

2015-10-24T13:56:37Z

The code path for receiving broadcast packets is currently distinct from the unicast path. This leads to unnecessary code and data duplication, something that can be avoided with some effort. We now introduce separate per-peer tipc_link instances for handling broadcast packet reception. Each receive link keeps a pointer to the common, single, broadcast link instance, and can hence handle release and retransmission of send buffers as if they belonged to the own instance. Furthermore, we let each unicast link instance keep a reference to both the pertaining broadcast receive link, and to the common send link. This makes it possible for the unicast links to easily access data for broadcast link synchronization, as well as for carrying acknowledges for received broadcast packets. Signed-off-by: Jon Maloy Reviewed-by: Ying Xue Signed-off-by: David S. Miller

tipc: introduce capability bit for broadcast synchronization

2015-10-24T13:56:35Z

Until now, we have tried to support both the newer, dedicated broadcast synchronization mechanism along with the older, less safe, RESET_MSG/ ACTIVATE_MSG based one. The latter method has turned out to be a hazard in a highly dynamic cluster, so we find it safer to disable it completely when we find that the former mechanism is supported by the peer node. For this purpose, we now introduce a new capabability bit, TIPC_BCAST_SYNCH, to inform any peer nodes that dedicated broadcast syncronization is supported by the present node. The new bit is conveyed between peers in the 'capabilities' field of neighbor discovery messages. Signed-off-by: Jon Maloy Reviewed-by: Ying Xue Signed-off-by: David S. Miller