On Fri, 2 Mar 2007 15:38:41 +0100
Eric Dumazet [off-list ref] wrote:

We currently use a special structure (struct skb_timeval) and plain 'struct 
timeval' to store packet timestamps in sk_buffs and struct sock.

This has some drawbacks :
- Fixed resolution of micro second.
- Waste of space on 64bit platforms where sizeof(struct timeval)=16

I suggest using ktime_t that is a nice abstraction of high resolution time 
services, currently capable of nanosecond resolution.

As sizeof(ktime_t) is 8 bytes, using ktime_t in 'struct sock' permits a 8 byte 
shrink of this structure on 64bit architectures. Some other structures also 
benefit from this size reduction (struct ipq in ipv4/ip_fragment.c, struct 
frag_queue in ipv6/reassembly.c, ...)

This is even better. Also comparing ktime_t's is easier if some code needs
to do that.