On Thu, Dec 17, 2015 at 12:18:36PM +0800, ?? wrote: > Hi all, > > > When running the multi process example, does anybody know that why increasing > the number of mbufs, the performance gets dropped. > > > In multi process example, there are two macros which are related to the > number of mbufs > > > #defineMBUFS_PER_CLIENT1536 > | > | #defineMBUFS_PER_PORT1536 | > | | > > > If increasing these two numbers by 8 times, the performance drops about 10%. > Does anybody know why? > > | constunsigned num_mbufs = (num_clients * MBUFS_PER_CLIENT) \ | > | | + (ports->num_ports * MBUFS_PER_PORT); | > | pktmbuf_pool = rte_mempool_create(PKTMBUF_POOL_NAME, num_mbufs, | > | | MBUF_SIZE, MBUF_CACHE_SIZE, | > | | sizeof(struct rte_pktmbuf_pool_private), rte_pktmbuf_pool_init, | > | | NULL, rte_pktmbuf_init, NULL, rte_socket_id(), NO_FLAGS ); |
One possible explanation could be due to the memory footprint of the memory pool. While the per-lcore mempool caches of buffers operate in a LIFO (i.e. stack) manner, when mbufs are allocated on one core and freed on another, they pass through a FIFO (i.e. ring) inside the mempool. This means that you iterate through all buffers in the pool in this case, which can cause a slowdown if the mempool size is bigger than your cache. /Bruce
