5. Stack Mempool Driver
rte_mempool_stack is a pure software mempool driver based on the
rte_stack DPDK library. For run-to-completion workloads with sufficiently
large per-lcore caches, the mbufs will likely stay in the per-lcore caches and
the mempool type (ring, stack, etc.) will have a negligible impact on
performance. However a stack-based mempool is often better suited to pipelined
packet-processing workloads (which allocate and free mbufs on different lcores)
than a ring-based mempool, since its LIFO behavior results in better temporal
locality and a minimal memory footprint even if the mempool is
over-provisioned. Users are encouraged to benchmark with multiple mempool types
to determine which works best for their specific application.
The following modes of operation are available for the stack mempool driver and can be selected as described in Mempool Handlers:
The underlying rte_stack operates in standard (lock-based) mode. For more information please refer to Lock-based Stack.
The underlying rte_stack operates in lock-free mode. For more information please refer to Lock-free Stack.
The standard stack outperforms the lock-free stack on average, however the standard stack is non-preemptive: if a mempool user is preempted while holding the stack lock, that thread will block all other mempool accesses until it returns and releases the lock. As a result, an application using the standard stack whose threads can be preempted can suffer from brief, infrequent performance hiccups.
The lock-free stack, by design, is not susceptible to this problem; one thread can be preempted at any point during a push or pop operation and will not impede the progress of any other thread.
For a more detailed description of the stack implementations, please refer to Stack Library.