Hello,
I would like to ask about asoc->rwnd_press in compared to asoc->rwnd.
sctp_assoc_rwnd_increase has next if case:
if (asoc->rwnd_press && asoc->rwnd >= asoc->rwnd_press)
I want ask community opinion about "asoc->rwnd >= asoc->rwnd_press"
I observed situation when association buffer was empty but "asoc->rwnd
>= asoc->rwnd_press"
returned false.
Next table shows this issue:
1. skb_payload = payload + skb; (skb==232)
2. If ulp will read all packets from buffer how much asoc->rwnd will be
rwnd_r = (sk_rcvbuf / skb_payload) * payload;
3. for current payload size and sk_rcvbuf size how big initialization
value will be for rwnd_press (in sctp_assoc_rwnd_decrease).
rwnd_press = sk_rcvbuf/2 - rwnd_r
On my laptop skb has sizeof(struct sk_buff) == 232 and sk_rcvbuf equal 212992.
payload skb_payload rwnd_r rwnd_press
...
16 248 13744 92752
//asoc->rwnd>=asoc->rwnd_press - false. but buffer empty.
17 249 14552 91944
18 250 15336 91160
19 251 16131 90365
20 252 16920 89576
21 253 17682 88814
22 254 18458 88038
23 255 19228 87268
24 256 19968 86528
25 257 20725 85771
26 258 21476 85020
27 259 22221 84275
28 260 22960 83536
29 261 23693 82803
30 262 24390 82106
31 263 25110 81386
32 264 25824 80672
...
64 296 46080 60416
65 297 46670 59826
66 298 47190 59306
67 299 47771 58725
68 300 48280 58216
69 301 48852 57644
70 302 49420 57076
71 303 49913 56583
72 304 50472 56024
73 305 51027 55469
74 306 51578 54918
75 307 52050 54446
76 308 52592 53904
77 309 53130 < 53366
78 310 53664 > 52832
//asoc->rwnd>=asoc->rwnd_press - true
79 311 54115 > 52381
80 312 54640 > 51856
Should it ("asoc->rwnd >= asoc->rwnd_press") stay false even when buffer empty?
I tested on my laptop next solution:
--- a/net/sctp/associola.c 2015-08-15 19:07:16.527696361 +0200
+++ b/net/sctp/associola.c 2015-08-15 20:08:22.407812656 +0200
@@ -1458,10 +1458,18 @@ void sctp_assoc_rwnd_increase(struct sct
* threshold. The idea is to recover slowly, but up
* to the initial advertised window.
*/
- if (asoc->rwnd_press && asoc->rwnd >= asoc->rwnd_press) {
- int change = min(asoc->pathmtu, asoc->rwnd_press);
- asoc->rwnd += change;
- asoc->rwnd_press -= change;
+ if (asoc->rwnd_press) {
+ int fr_count = asoc->base.sk->sk_rcvbuf;
+ if (asoc->ep->rcvbuf_policy)
+ fr_count -= atomic_read(&asoc->rmem_alloc);
+ else
+ fr_count -= atomic_read(&asoc->base.sk->sk_rmem_alloc);
+
+ if (fr_count > 0 && ((fr_count >> 1) >= asoc->rwnd_press)) {
+ int change = min(asoc->pathmtu, asoc->rwnd_press);
+ asoc->rwnd += change;
+ asoc->rwnd_press -= change;
+ }
}
pr_debug("%s: asoc:%p rwnd increased by %d to (%u, %u) - %u\n",
--
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