Dynamic protection of shared memory used by output queues in a network device

An apparatus comprising:

• network ports to receive and send network packets from and to a network;
• and
• a controller coupled to the network ports, the controller including a buffer with buffer space to store network packets linked to queues to feed the packets to ones of the network ports associated with the queues, the buffer space being shared dynamically among multiple traffic pools, the controller configured to:
• determine per-pool dynamic thresholds defining upper limits for per-pool occupancy each based on an amount of unused buffer space;
• determine per-queue dynamic thresholds defining upper limits for per-queue occupancy based on amounts of unused buffer space available in the pools with which the queues are associated;
• determine if there are unused packet descriptors (PDs) available to a given pool based on a pool dynamic threshold for PDs;
• determine, for each queue, a queue dynamic threshold for PDs so as to define a maximum number of PDs available to the queue that is based on a number of unused PDs available to the given pool, wherein the queue dynamic threshold for PDs is determined based on an average fanout of packets in the given pool, the average fanout being a ratio of (a) a number of PDs used by the given pool, and (b) a pool occupancy for the given pool;
• and
• receive packets from the input ports, and for each received packet:
• for the queue for which the packet is destined, reduce the determined per-queue dynamic threshold by a random amount;
• admit the packet to the pool with which the packet is associated and the queue for which the packet is destined if (i) occupancy of the associated pool is less than the corresponding per-pool dynamic threshold, (ii) occupancy of the queue for which the packet is destined is less than the corresponding reduced per-queue dynamic threshold, (iii) there are unused PDs available to the associated pool, and (iv) usage of PDs for the queue for which the packet is destined is less than the queue dynamic threshold for PDs;
• drop the packet if conditions (i) to (iv) are not met;
• and
• in response to admitting the packet, assign a packet descriptor to the packet, wherein the packet descriptor includes a first pointer pointing to an address of the packet in the buffer, and wherein a second pointer of a last packet descriptor previously linked to the queues is set to point to the packet descriptor.

A non-transitory computer-readable medium encoded with instructions which, when executed by a controller of a network device including a buffer having buffer space to store network packets linked to queues to feed the packets to output ports of the network device associated with the queues, the buffer space being shared dynamically among multiple traffic pools, cause the controller to perform operations including:

• determining per-pool dynamic thresholds defining upper limits for per-pool occupancy each based on an amount of unused buffer space;
• determining per-queue dynamic thresholds defining upper limits for per-queue occupancy based on amounts of unused buffer space available in the pools with which the queues are associated;
• determining if there are unused packet descriptors (PDs) available to a given pool based on a pool dynamic threshold for PDs;
• determining, for each queue, a queue dynamic threshold for PDs so as to define a maximum number of PDs available to the queue that is based on a number of unused PDs available to the given pool, wherein the queue dynamic threshold for PDs is determined based on an average fanout of packets in the given pool, the average fanout being a ratio of (a) a number of PDs used by the given pool, and (b) a pool occupancy for the given pool;
• and
• receiving packets, and for each received packet:
• for the queue for which the packet is destined, reducing the determined per-queue dynamic threshold by a random amount;
• admitting the packet to the pool with which the packet is associated and the queue for which the packet is destined if (i) occupancy of the associated pool is less than the corresponding per-pool dynamic threshold, (ii) occupancy of the queue for which the packet is destined is less than the corresponding reduced per-queue dynamic threshold, (iii) there are unused PDs available to the associated pool, and (iv) usage of PDs for the queue for which the packet is destined is less than the queue dynamic threshold for PDs;
• dropping the packet if conditions (i) to (iv) are not met;
• and
• in response to admitting the packet, assigning a packet descriptor to the packet, wherein the packet descriptor includes a first pointer pointing to an address of the packet in the buffer, and wherein a second pointer of a last packet descriptor previously linked to the queues is set to point to the packet descriptor.