On Fri, 12 Mar 2004 09:15:05 -0800
Stephen Hemminger <shemminger@xxxxxxxx> wrote:
>Found this while looking in detail at TCP. The westwood.bw_sample element
>it tcp_opt is set but not used by the existing code in 2.6.4
Stephen,
I used that field in the first version of the Westwood code just for having
the possibility of doing a bandwidth estimation tracking analysis.
After dropping CONFIG_TCP_WESTWOOD_STATS it's simply useless and so I agree
with your patch. But it's necessary to just point out an important thing.
When you call westwood_filter() you're actually evaluating the bandwidth
estimate. This is done by two constant coefficients low-pass filters one
after the other.
This part of the code was taken clearly separated from the rest of the code
since you could even find a better way to do it (f.e. TCP Westwood which came
before Westwood+ did it in improper manner). Maybe this was the reason
bw_sample was left in the struct westwood. But being it absolutely useless
at this time it could be removed even from there. I simply dropped another
line wrt to your patch.
Regards.
--
Angelo Dell'Aera 'buffer'
Antifork Research, Inc. http://buffer.antifork.org
diff -Naur linux-2.6.4-old/include/linux/tcp.h linux-2.6.4/include/linux/tcp.h
--- linux-2.6.4-old/include/linux/tcp.h 2004-02-18 16:34:15.000000000 +0100
+++ linux-2.6.4/include/linux/tcp.h 2004-03-13 16:56:39.000000000 +0100
@@ -377,7 +377,6 @@
/* TCP Westwood structure */
struct {
- __u32 bw_sample; /* bandwidth sample */
__u32 bw_ns_est; /* first bandwidth estimation..not
too smoothed 8) */
__u32 bw_est; /* bandwidth estimate */
__u32 rtt_win_sx; /* here starts a new evaluation...
*/
diff -Naur linux-2.6.4-old/net/ipv4/tcp_input.c linux-2.6.4/net/ipv4/tcp_input.c
--- linux-2.6.4-old/net/ipv4/tcp_input.c 2004-03-10 17:31:40.000000000
+0100
+++ linux-2.6.4/net/ipv4/tcp_input.c 2004-03-13 16:50:35.000000000 +0100
@@ -2065,7 +2065,6 @@
{
struct tcp_opt *tp = tcp_sk(sk);
- tp->westwood.bw_sample = 0;
tp->westwood.bw_ns_est = 0;
tp->westwood.bw_est = 0;
tp->westwood.accounted = 0;
@@ -2088,14 +2087,13 @@
static void westwood_filter(struct sock *sk, __u32 delta)
{
struct tcp_opt *tp = tcp_sk(sk);
- __u32 sample = tp->westwood.bk / delta;
tp->westwood.bw_ns_est =
- westwood_do_filter(tp->westwood.bw_ns_est, sample);
+ westwood_do_filter(tp->westwood.bw_ns_est,
+ tp->westwood.bk / delta);
tp->westwood.bw_est =
westwood_do_filter(tp->westwood.bw_est,
tp->westwood.bw_ns_est);
- tp->westwood.bw_sample = sample;
}
/* @westwood_update_rttmin
|