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- Join Date
- Oct 2008
questions regarding implement new TCP congestion algorithm in kernel
I'm using Fedora 9 with kernel 220.127.116.11-108.fc9.i686 to implement new congestion algorithm.
I want to measure the round trip time (RTT) of acked pkt. From Linux modular congestion control - WiL, I know that void pkts_acked(struct sock *sk, u32 cnt, s32 rtt_us) can be used with rtt_us is the RTT.
However, I want to get the RTT of the acked pkt inside void (*cong_avoid)(struct sock *sk, u32 ack, u32 in_flight)? How could I do that?
In addition, I get confused when it's said that pkts_acked is called when ACK arrives but cong_avoid is also called when ACK arrives? So what's the difference between those two?
Moreover, I want to measure the time (in ms) of last ACK and new arrived ACK to find the difference as a input for a formula. Besides using current_kernel_time() in include/linux/time.h what is a better alternative way to do this? I saw an advice using rdtsc*() macro at get time inside kernel | KernelTrap.
I use (HZ/200) ~ 5ms. Is it correct?