Re: [RFC]: tfrc_tx_hist_rtt

2007-11-30 Thread Arnaldo Carvalho de Melo 
Em Fri, Nov 30, 2007 at 12:19:36PM +, Gerrit Renker escreveu:
 Sorry I only got this email today and it is a busy day, too.
 
 The changes look good and are in general a further improvement on the
 code. I like the idea of hiding the internals of the list structure in 
 the source file.
 
 I wonder if one could go one step further and also take the timestamp
 directly when looking up the previous history sample, e.g.
 
   u32 tfrc_tx_hist_rtt(struct tfrc_tx_hist_entry *head, const u64 seqno)
   {
   u32 rtt = 0;
   struct tfrc_tx_hist_entry *packet = 
 tfrc_tx_hist_find_entry(head, seqno);
   
   if (packet != NULL) {
   rtt = ktime_us_delta(ktime_get_real(), packet-stamp);
   /*
* Garbage-collect older (irrelevant) entries:
*/
   tfrc_tx_hist_purge(packet-next);
   }
   
   return rtt;
   }
 
 Just a suggestion.

I thought about that, but ccid3_hc_tx_packet_recv needs a timestamp some
lines below, when we reuse the ktime_get_real call.

- Arnaldo
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Re: [RFC]: tfrc_tx_hist_rtt

2007-11-30 Thread Gerrit Renker 
Sorry I only got this email today and it is a busy day, too.

The changes look good and are in general a further improvement on the
code. I like the idea of hiding the internals of the list structure in 
the source file.

I wonder if one could go one step further and also take the timestamp
directly when looking up the previous history sample, e.g.

u32 tfrc_tx_hist_rtt(struct tfrc_tx_hist_entry *head, const u64 seqno)
{
u32 rtt = 0;
struct tfrc_tx_hist_entry *packet = 
tfrc_tx_hist_find_entry(head, seqno);

if (packet != NULL) {
rtt = ktime_us_delta(ktime_get_real(), packet-stamp);
/*
 * Garbage-collect older (irrelevant) entries:
 */
tfrc_tx_hist_purge(packet-next);
}

return rtt;
}

Just a suggestion.

Thanks for looking through this.
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Re: [RFC]: tfrc_tx_hist_rtt

2007-11-30 Thread Gerrit Renker 
|  I wonder if one could go one step further and also take the timestamp
|  directly when looking up the previous history sample, e.g.
|  
snip
| 
| I thought about that, but ccid3_hc_tx_packet_recv needs a timestamp some
| lines below, when we reuse the ktime_get_real call.
| 
Oh, of course - that was real stupid of me. I think it is even in two occasions 
where a 
timestamp is needed, below in the same function.

I am really hoping that some time there is a robust RFC1323-like algorithm,
this could solve all the RTT sampling for both CCID2 and CCID3 (also CCID4),
and then there would be a RTT available in the main module (e.g. for better
estimating the Close/CloseReq retransmission timeout).


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[RFC]: tfrc_tx_hist_rtt

2007-11-29 Thread Arnaldo Carvalho de Melo 
Hi Gerrit,

Coming back to hiding the TX history data structures, take a
look at what I'm commiting to my tree:

1. struct tfrc_tx_hist_entry is completely hidden in
   net/dccp/ccids/lib/packet_history.c
2. I found tfrc_tx_hist_when confusing and returning two results, if it
   had found the ackno in the history and the timestamp, so I introduced
   tfrc_tx_hist_rtt instead, that returns 0 if the ackno was not found.

Does this looks reasonable?

- Arnaldo

diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c
index 2668de8..5dea690 100644
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -399,7 +399,6 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct 
sk_buff *skb)
 {
struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
struct ccid3_options_received *opt_recv;
-   struct tfrc_tx_hist_entry *packet;
ktime_t now;
unsigned long t_nfb;
u32 pinv, r_sample;
@@ -414,19 +413,17 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, 
struct sk_buff *skb)
switch (hctx-ccid3hctx_state) {
case TFRC_SSTATE_NO_FBACK:
case TFRC_SSTATE_FBACK:
+   now = ktime_get_real();
+
/* estimate RTT from history if ACK number is valid */
-   packet = tfrc_tx_hist_find_entry(hctx-ccid3hctx_hist,
-
DCCP_SKB_CB(skb)-dccpd_ack_seq);
-   if (packet == NULL) {
+   r_sample = tfrc_tx_hist_rtt(hctx-ccid3hctx_hist,
+   DCCP_SKB_CB(skb)-dccpd_ack_seq, 
now);
+   if (r_sample == 0) {
DCCP_WARN(%s(%p): %s with bogus ACK-%llu\n, 
dccp_role(sk), sk,
  
dccp_packet_name(DCCP_SKB_CB(skb)-dccpd_type),
  (unsigned long 
long)DCCP_SKB_CB(skb)-dccpd_ack_seq);
return;
}
-   /*
-* Garbage-collect older (irrelevant) entries
-*/
-   tfrc_tx_hist_purge(packet-next);
 
/* Update receive rate in units of 64 * bytes/second */
hctx-ccid3hctx_x_recv = opt_recv-ccid3or_receive_rate;
@@ -438,12 +435,10 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, 
struct sk_buff *skb)
hctx-ccid3hctx_p = 0;
else   /* can not exceed 100% */
hctx-ccid3hctx_p = 100 / pinv;
-
-   now = ktime_get_real();
/*
-* Calculate new RTT sample and update moving average
+* Validate new RTT sample and update moving average
 */
-   r_sample = dccp_sample_rtt(sk, ktime_us_delta(now, 
packet-stamp));
+   r_sample = dccp_sample_rtt(sk, r_sample);
hctx-ccid3hctx_rtt = tfrc_ewma(hctx-ccid3hctx_rtt, r_sample, 
9);
 
if (hctx-ccid3hctx_state == TFRC_SSTATE_NO_FBACK) {
diff --git a/net/dccp/ccids/lib/packet_history.c 
b/net/dccp/ccids/lib/packet_history.c
index 1397360..4805de9 100644
--- a/net/dccp/ccids/lib/packet_history.c
+++ b/net/dccp/ccids/lib/packet_history.c
@@ -39,12 +39,24 @@
 #include linux/string.h
 #include packet_history.h
 
+/**
+ *  tfrc_tx_hist_entry  -  Simple singly-linked TX history list
+ *  @next:  next oldest entry (LIFO order)
+ *  @seqno: sequence number of this entry
+ *  @stamp: send time of packet with sequence number @seqno
+ */
+struct tfrc_tx_hist_entry {
+   struct tfrc_tx_hist_entry *next;
+   u64   seqno;
+   ktime_t   stamp;
+};
+
 /*
  * Transmitter History Routines
  */
 static struct kmem_cache *tfrc_tx_hist;
 
-struct tfrc_tx_hist_entry *
+static struct tfrc_tx_hist_entry *
tfrc_tx_hist_find_entry(struct tfrc_tx_hist_entry *head, u64 seqno)
 {
while (head != NULL  head-seqno != seqno)
@@ -52,7 +64,6 @@ struct tfrc_tx_hist_entry *
 
return head;
 }
-EXPORT_SYMBOL_GPL(tfrc_tx_hist_find_entry);
 
 int tfrc_tx_hist_add(struct tfrc_tx_hist_entry **headp, u64 seqno)
 {
@@ -83,6 +94,24 @@ void tfrc_tx_hist_purge(struct tfrc_tx_hist_entry **headp)
 }
 EXPORT_SYMBOL_GPL(tfrc_tx_hist_purge);
 
+u32 tfrc_tx_hist_rtt(struct tfrc_tx_hist_entry *head, const u64 seqno,
+const ktime_t now)
+{
+   u32 rtt = 0;
+   struct tfrc_tx_hist_entry *packet = tfrc_tx_hist_find_entry(head, 
seqno);
+
+   if (packet != NULL) {
+   rtt = ktime_us_delta(now, packet-stamp);
+   /*
+* Garbage-collect older (irrelevant) entries:
+*/
+   tfrc_tx_hist_purge(packet-next);
+   }
+
+   return rtt;
+}
+EXPORT_SYMBOL_GPL(tfrc_tx_hist_rtt);
+
 /*
  * Receiver History Routines
  */
diff --git a/net/dccp/ccids/lib/packet_history.h 
b/net/dccp/ccids/lib/packet_history.h
index 5c07182..0670f46 100644
---