On Sunday, August 10, 2014 4:09:55 pm David Bar wrote:
Hi
(Forgive me if this topic has been discussed before. I didn't find it in
the archives)
In tcp_input(), when a packet is received on an established socket the code
re-arms the keep-alive timer, for each packet.
Here:
https://svnweb.freebsd.org/base/release/10.0.0/sys/netinet/tcp_input.c?revision=260789view=markup#l1518
Isn't this a waste to do this for each packet?
The setting of the timer when the connection becomes established should
suffice if there was a small change in tcp_timer_keep().
If tcp_timer_keep() would first checks if tp-t_rcvtime is recent (newer
than the TT_KEEPIDLE time), and would just re-arm the timer to go off
later, then we would keep the same functionality.
I can't think of any downsides to this idea. Any good reason why this
hasn't been done before?
I think it is just a tradeoff between having the timer run at all. However, I
suspect that with high packet rates it probably is cheaper to have the timer
run periodically and reschedule itself if it notices it isn't needed as you
suggested. Do you want to write up a patch and test it?
--
John Baldwin
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