System and method for low-overhead monitoring of transmit queue empty status
View Patent ↗A queue monitoring system and method determines when one or more transmit queues have reached a state that requires action by the host processing device, without the need for periodic polling of transmit status or excessive interrupt servicing. The queue monitoring implements an interrupt mechanism that generates an interrupt if one or more of the transmit queues has gone from a non-empty state to an empty state, and remained in the empty state for a (programmable) period of time. The combination of queue status checking (when adding new transmit data) with the queue monitoring interrupt mechanism removes the need for periodic polling of queue status and handling of interrupts generation on the completed transmission of data from one or more transmit buffer.
1. A system for sending data, said system comprising:
a host processor including a host processor memory that stores copies of data packets; and
a transmit device coupled to said host processor that receives, stores, and transmits said data packets, said transmit device including:
a transmit device memory that stores said data packets until said data packets are transmitted, and
a state machine coupled to said transmit device memory that monitors for when said transmit device memory receives and transmits said data packets to determine when an interrupt should be sent to said host processor to clear said copies of said data packets from said host processor memory, wherein said state machine comprises,
a monitor that determines a status of said transmit device memory;
a counter that starts counting once said monitor determines said status has transitioned from a not-empty state to an empty state; and
an interrupt signal generator that generates an interrupt signal when said counter reaches a threshold value.
2. The system of claim 1 , wherein said state machine further comprises:
a counter monitor coupled to said counter; and
a threshold value memory coupled to said counter monitor that stores said threshold value;
wherein said counter monitor determines if said counter has reached said threshold value to trigger said interrupt signal generator to generate said interrupt signal.
3. A method of monitoring a queue in a transmit device of a communications network, said method comprising the steps of:
a) storing data packets in a host processor queue;
b) sending said data packets to said queue in said transmit device causing said queue in said transmit device to transition to a not-empty state;
c) monitoring said queue in said transmit device to determine when said queue transitions from said not-empty state back to an empty state;
d) starting a counter when said queue in said transmit device transitions from said not-empty state to said empty state; and
e) generating an interrupt signal when a counter value in said counter reaches a threshold value
(f) sending said interrupt signal to a host processor; and
(g) clearing said host processor queue when said interrupt signal is received.
4. A method of monitoring queue status, comprising the steps of:
detecting when a queue has changed from an empty state to a not-empty state;
starting a watchdog counter when said queue transitions back to said empty state; and
generating an interrupt signal when said watchdog counter equals a watchdog value;
sending said interrupt signal to a host processor; and
clearing a memory space of said host processor upon receipt of said interrupt signal.