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Transmitted skb might be attached to a socket and a destructor, for memory accounting purposes. Traditionally, this destructor is called at tx completion time, when skb is freed. When tx completion is performed by another cpu than the sender, this forces some cache lines to change ownership. XPS was an attempt to give tx completion to initial cpu. David idea is to call destructor right before giving skb to device (call to ndo_start_xmit()). Because device queues are usually small, orphaning skb before tx completion is not a big deal. Some drivers already do this, we could do it in upper level. There is one known exception to this early orphaning, called tx timestamping. It needs to keep a reference to socket until device can give a hardware or software timestamp. This patch adds a skb_orphan_try() helper, to centralize all exceptions to early orphaning in one spot, and use it in dev_hard_start_xmit(). "tbench 16" results on a Nehalem machine (2 X5570 @ 2.93GHz) before: Throughput 4428.9 MB/sec 16 procs after: Throughput 4448.14 MB/sec 16 procs UDP should get even better results, its destructor being more complex, since SOCK_USE_WRITE_QUEUE is not set (four atomic ops instead of one) Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net> |
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| .. | ||
| datagram.c | ||
| dev_addr_lists.c | ||
| dev.c | ||
| drop_monitor.c | ||
| dst.c | ||
| ethtool.c | ||
| fib_rules.c | ||
| filter.c | ||
| flow.c | ||
| gen_estimator.c | ||
| gen_stats.c | ||
| iovec.c | ||
| kmap_skb.h | ||
| link_watch.c | ||
| Makefile | ||
| neighbour.c | ||
| net_namespace.c | ||
| net-sysfs.c | ||
| net-sysfs.h | ||
| net-traces.c | ||
| netevent.c | ||
| netpoll.c | ||
| pktgen.c | ||
| request_sock.c | ||
| rtnetlink.c | ||
| scm.c | ||
| skbuff.c | ||
| sock.c | ||
| stream.c | ||
| sysctl_net_core.c | ||
| user_dma.c | ||
| utils.c | ||