| Message ID | 49BB72FA.1080401@cosmosbay.com |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
From: Eric Dumazet <dada1@cosmosbay.com> Date: Sat, 14 Mar 2009 10:03:54 +0100 > On x86_64, its rather unfortunate that "wait_queue_head_t wait" > field of "struct socket" spans two cache lines (assuming a 64 > bytes cache line in current cpus) > > offsetof(struct socket, wait)=0x30 > sizeof(wait_queue_head_t)=0x18 > > This might explain why Kenny Chang noticed that his multicast workload > was performing bad with 64 bit kernels, since more cache lines ping pongs > were involved. > > This litle patch moves "wait" field next "fasync_list" so that both > fields share a single cache line, to speedup sock_def_readable() > > Signed-off-by: Eric Dumazet <dada1@cosmosbay.com> Applied, thanks a lot Eric. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/include/linux/net.h b/include/linux/net.h index 4515efa..4fc2ffd 100644 --- a/include/linux/net.h +++ b/include/linux/net.h @@ -129,11 +129,15 @@ struct socket { socket_state state; short type; unsigned long flags; - const struct proto_ops *ops; + /* + * Please keep fasync_list & wait fields in the same cache line + */ struct fasync_struct *fasync_list; + wait_queue_head_t wait; + struct file *file; struct sock *sk; - wait_queue_head_t wait; + const struct proto_ops *ops; }; struct vm_area_struct;
On x86_64, its rather unfortunate that "wait_queue_head_t wait" field of "struct socket" spans two cache lines (assuming a 64 bytes cache line in current cpus) offsetof(struct socket, wait)=0x30 sizeof(wait_queue_head_t)=0x18 This might explain why Kenny Chang noticed that his multicast workload was performing bad with 64 bit kernels, since more cache lines ping pongs were involved. This litle patch moves "wait" field next "fasync_list" so that both fields share a single cache line, to speedup sock_def_readable() Signed-off-by: Eric Dumazet <dada1@cosmosbay.com> -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html