On 04/16/2014 08:50 PM, Vlad Yasevich wrote:
On 04/16/2014 05:02 AM, Alexander Sverdlin wrote:
Hi Dongsheng!
On 16/04/14 10:39, ext Dongsheng Song wrote:
>From my testing, netperf throughput from 600 Mbit/s drop to 6 Mbit/s,
the penalty is 99 %.
The question was, do you see this as a problem of the new rwnd algorithm?
If yes, how exactly?
[ Default config ./test_timetolive from lksctp-test suite triggered
that as well actually it appears, i.e. showing that the app never
woke up from the 3 sec timeout. ]
The algorithm isn't wrong, but the implementation appears to have
a bug with window update SACKs. The problem is that
sk->sk_rmem_alloc is updated by the skb destructor when
skb is freed. This happens after we call sctp_assoc_rwnd_update()
which tries to send the update SACK. As a result, in default
config with per-socket accounting, the test
if ((asoc->base.sk->sk_rcvbuf - rx_count) > 0)
uses the wrong values for rx_count and results in advertisement
of decreased rwnd instead of what is really available.
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