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SubjectRe: 100Mbps TCP stalls in 2.1.115
On Sun, Aug 09, 1998 at 02:36:49AM +0200, Zlatko Calusic wrote:
> Andi Kleen <ak@muc.de> writes:
>
> > Zlatko Calusic <Zlatko.Calusic@CARNet.hr> writes:
> > >
> > > E. g. FTP between two 100mbit hosts, transfer rate is ~50kb/sec, but
> > > many times it recovers after few (or few tens of) seconds.
> > >
> > > Sometimes it works, sometimes not. Tcpdump logs available on request.
> > >
> > > Any clue?
> >
> > What does /proc/net/netstat say after such a stall?
>
> {atlas} [~]% cat /proc/net/netstat
> TcpExt: SyncookiesSent SyncookiesRecv SyncookiesFailedEmbryonicRsts
> TcpExt: 0 0 0 0

You need a kernel >= 2.1.114 for useful output, sorry.

>
>
> > Also could you try to reproduce it with sockets that have the SO_DEBUG
> > flag set ?
> >
>
> I should take my favorite TCP application and recompile with one
> additional setsockopt in code, am I right?
> I never did SO_DEBUG's. :)
>
> I noticed that stalls are periodical, with period of about 2-3
> minutes.
>
> I made a long ping session, and came up with this:
>
> PING div.srce.hr (161.53.3.13): 56 data bytes
> 64 bytes from 161.53.3.13: icmp_seq=0 ttl=253 time=1.3 ms
> 64 bytes from 161.53.3.13: icmp_seq=1 ttl=253 time=1.1 ms
> 64 bytes from 161.53.3.13: icmp_seq=2 ttl=253 time=1.1 ms
> 64 bytes from 161.53.3.13: icmp_seq=3 ttl=253 time=1.0 ms
> 64 bytes from 161.53.3.13: icmp_seq=4 ttl=253 time=1.1 ms
> ... everything's ok, when ping times are around 1ms
> 64 bytes from 161.53.3.13: icmp_seq=147 ttl=253 time=1.0 ms
> 64 bytes from 161.53.3.13: icmp_seq=148 ttl=253 time=1.0 ms
> ... from now on, things are dog slow...
> 64 bytes from 161.53.3.13: icmp_seq=150 ttl=253 time=2.1 ms
> 64 bytes from 161.53.3.13: icmp_seq=151 ttl=253 time=2.0 ms
> 64 bytes from 161.53.3.13: icmp_seq=152 ttl=253 time=2.0 ms
> 64 bytes from 161.53.3.13: icmp_seq=153 ttl=253 time=2.1 ms
> 64 bytes from 161.53.3.13: icmp_seq=154 ttl=253 time=2.1 ms
> 64 bytes from 161.53.3.13: icmp_seq=155 ttl=253 time=2.1 ms
> 64 bytes from 161.53.3.13: icmp_seq=156 ttl=253 time=2.1 ms
> 64 bytes from 161.53.3.13: icmp_seq=157 ttl=253 time=74.9 ms
> 64 bytes from 161.53.3.13: icmp_seq=158 ttl=253 time=28.1 ms
> 64 bytes from 161.53.3.13: icmp_seq=161 ttl=253 time=2.2 ms
> 64 bytes from 161.53.3.13: icmp_seq=163 ttl=253 time=2.1 ms
> ...
> 64 bytes from 161.53.3.13: icmp_seq=335 ttl=253 time=2.1 ms
> 64 bytes from 161.53.3.13: icmp_seq=336 ttl=253 time=2.0 ms
> ... from now on, things are working correctly again...
> 64 bytes from 161.53.3.13: icmp_seq=337 ttl=253 time=1.1 ms
> 64 bytes from 161.53.3.13: icmp_seq=338 ttl=253 time=1.1 ms
> ... and so on...

If ping is slow too it is probably a network driver problem,
not a TCP problem.

-Andi

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