On March 2, 2007 01:54:45 pm John Heffner wrote:
> Alex Sidorenko wrote:
> [snip]
>
> > --- net/ipv4/tcp_output.c.orig Wed May 3 20:40:43 2006
> > +++ net/ipv4/tcp_output.c Tue Jan 30 14:24:56 2007
> > @@ -641,6 +641,7 @@
> > * Note, we don't "adjust" for TIMESTAMP or SACK option bytes.
> > * Regular options like TIMESTAMP are taken into account.
> > */
> > +static const char *SWS_id_string="@#SWS-fix-2";
> > u32 __tcp_select_window(struct sock *sk)
> > {
> > struct tcp_opt *tp = &sk->tp_pinfo.af_tcp;
> > @@ -682,6 +683,9 @@
> > window = tp->rcv_wnd;
> > if (window <= free_space - mss || window > free_space)
> > window = (free_space/mss)*mss;
> > + /* A fix for small rcvbuf [EMAIL PROTECTED] */
> > + else if (mss == full_space && window < full_space/2)
> > + window = full_space/2;
> >
> > return window;
> > }
>
> Good analysis of the problem, but the patch does not look quite right.
> In particular, you can't ever announce a zero window. :)
Hi John,
in case when (free_space < full_space/2) we do not reach the modified code and
we will return zero:
if (free_space < full_space/2) {
icsk->icsk_ack.quick = 0;
if (tcp_memory_pressure)
tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U*tp->advmss);
if (free_space < mss)
return 0;
}
Here is how windows look with the fixed kernel (from customer's test):
20:59:45.320758 Node1.logical.40171 > 11.0.0.1.39909: win = 708
20:59:45.322758 Node1.logical.40171 > 11.0.0.1.39909: win = 288
20:59:45.714567 Node1.logical.40171 > 11.0.0.1.39909: win = 354
20:59:45.717110 Node1.logical.40171 > 11.0.0.1.39909: win = 0
20:59:45.719110 Node1.logical.40171 > 11.0.0.1.39909: win = 708
...
Regards,
Alex
> I think this attached patch does the correct SWS avoidance.
>
> Thanks,
> -John
--
------------------------------------------------------------------
Alexandre Sidorenko email: [EMAIL PROTECTED]
Global Solutions Engineering: Unix Networking
Hewlett-Packard (Canada)
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