A device includes ports, a packet processor, and a memory management circuit. The ports communicate packets over a network. The packet processor processes the packets using queues. The memory management circuit maintains a shared buffer in a memory and adaptively allocates memory resources from the shared buffer to the queues, maintains in the memory, in addition to the shared buffer, a shared-reserve memory pool for use by the queues, identifies, among the queues, a queue that requires additional memory resources, the queue having an occupancy that is (i) above a current value of a dynamic threshold, rendering the queue ineligible for additional allocation from the shared buffer, and (ii) no more than a defined margin above the current value of the dynamic threshold, rendering the queue eligible for allocation from the shared-reserve memory pool, and allocates memory resources to the identified queue from the shared-reserve memory pool.