Re: [net-next] tcp: do tcp_mstamp_refresh before retransmits on TSQ handler

On Mon, 2017-10-23 at 12:26 +0900, Koichiro Den wrote:

Now I wonder this is more of a theoretical one rather than a patch to fix one
specific bug.

Note that I said that your patch was fine and I added a 'Reviewed-by:'
tag.


What I meant is that it has no direct effect on correctness of TCP
stack. I could not cook a packetdrill test that shows the difference
before and after your patch.

BTW, in the following sequence :

A)   Fetch high-res timestamp and store in X
B)   Use X

B) Can use a quite old value of X, depending on scheduling (preempt
kernels or interrupt handling)

TCP really does not care of how accurate X is, it is a best effort.

For RTX packets, it is even more the case, since TCP does not take RTT
samples from packets that were retransmitted.