Deadlock avoidance and deadlock recovery in DIN
Due to the situation where the resource occupier applies for another resource, in DIN, because the topology itself has a ring path, it is easy to deadlock in DIN. As shown in Figure 2, A, B, C, and D are the paths of four packets (Path) forming a loop to form a deadlock. Document [4] discusses the problem of deadlock in the interconnection structure, and proposes to use the channel dependency graph (channel dependency graph, CDG) whether there is a cycle to determine whether the deadlock. Literature [6] improved this method and affirmed the sufficiency and necessity of CDG graphs, that is, there is no deadlock when the CDG graph cycle occurs dynamically.
The methods to solve the deadlock can be divided into two categories: deadlock avoidance and deadlock recovery. Deadlock avoidance refers to preventing path loops by disabling certain resources in routing algorithm settings. Reference [10] breaks the loop by restricting routing in one direction to avoid deadlock. The routing algorithms in this article 2 also use deadlock avoidance strategies. Deadlock avoidance is to prevent deadlock by restricting the use of some resources (cache or physical channel), so the resource utilization of the switch fabric is not high.
Deadlock recovery is to solve the deadlock through a certain strategy after finding a deadlock in the structure. Allows the group to use any resources in the switching structure to improve the resource utilization of the switching structure. There are generally two methods of deadlock recovery. The passive deadlock recovery method uses discarding and offset routing to handle deadlock packets. The active deadlock recovery method transfers deadlock packets to the target node by allocating other resources. The decision on deadlock is a difficulty in the deadlock recovery mechanism, especially when the service load and packet length vary widely. How to quickly distinguish whether a packet is blocked or deadlocked. The deadlock recovery mechanism based on latency is discussed in [11]. Literature [12] introduced a distributed deadlock detection mechanism, which uses the method of judging the root node in a blocking packet to reduce the false positive rate.
Figure 2 A, B, C, D 4 groups constitute a deadlock
It is more suitable to adopt the deadlock recovery mechanism in the data exchange structure. In the data exchange technology, the entire structure has limited resources, and the data exchange has higher requirements on the transmission bandwidth. The data recovery mechanism needs to be combined with an adaptive routing algorithm to reduce the incidence of deadlocks. Therefore, it is very necessary to analyze the occurrence of deadlock of various routing algorithms.
Application Analysis of Direct Interconnect Structure in Data Exchange
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