$cat /proc/sys/net/ipv4/tcp_dma_copybreak 4096 $ tcp_dma_copybreak – INTEGER Lower limit, in bytes, of the size of socket reads that will be offloaded to a DMA copy engine, if one is present in the system and CONFIG_NET_DMA is enabled. Default: 4096 grepping through linux kernel source 2.6.32 sysctl_net_ipv4.c: .procname = “tcp_dma_copybreak”,