[ECOS] Re: Few questions on lwip stack

[Alexander Aganichev]

On Wed, Nov 17, 2010 at 11:56 PM, Sergei Gavrikov
<sergei.gavrikov@gmail.com> wrote:
> On Wed, 17 Nov 2010, Alexander Aganichev wrote:
>
>> On Tue, Nov 16, 2010 at 6:18 PM, Alexander Aganichev
>> <aaganichev@gmail.com> wrote:
>>>
>>> Now I have a problem that lwip sometimes ignores IP frames from PC
>>> which cause PC to retransmit frame after two seconds which is not
>>> acceptable. This happens not under heavy load. Never saw anything
>>> similar on previous lwip version. The response time on ICMP is very
>>> good and I don't see any delay or ignorance...  Just wondering if
>>> anyone saw something similar and have ideas where to dig?
>>
>> It looks like tcp_tmr() is not executed in sequential mode and this
>> cause the problem. Can it just be started from tcpip_thread() like
>> other timers?
>
> Hi,
>
> Can you provide your ecm file/test? Of curiosity I tried eCos `tcpecho'
> test under some load and I did not observe the same fading.
>
> Having no real H/W  I used something virtual
>
>  eCos:     CVS updated
>  Host:     Linux
>  Target:   pc_rltk8139
>  Template: lwip_eth
>  Startup:  RAM
>  Hardware: QEMU
>  Test:     tcpecho
>  Run land: GDB (i386-elf-gdb)
>
>  Only changed:
>
>  cdl_option CYGFUN_LWIP_MODE_SIMPLE {
>      user_value 0
>  };
>  cdl_option CYGFUN_LWIP_MODE_SEQUENTIAL {
>      user_value 1
>  };
>
>  Stress Fu:
>
>  % strings /dev/urandom | nc host port   ;# port was mapped on 7th
>
> I saw l-o-o-o-ng and continuous 'matrix' in terminal. No fading. After
> STOP/CONT (I got a resumption of the run as I expected) Well, it was
> lazy and not accurate test, it was virtual H/W  (but real S/W) and I
> could not reproduce the issue for my environment. However, I guess the
> packets could be lost (I was looking only for any long fading and I did
> not plan to dive in the dumps of network traffic). Also, I call that
> default CDL options (like mine) cannot be suitable for stress conditions
> (i.e.  default sizes of net buffers, the stack sizes, etc.).

My target board is quite slow on Ethernet and HyperTerminal broke
sending data in multiple small packets, so probably that's why I was
able to reach point where no more pbufs could be allocated.

> Seek the posts near the time of porting new LWIP version, please, I hope that
> Simon gave some advices.

It looks like the root of my problem is in the way I created tasks. I
used POSIX message queues and POSIX threads. After switching I left
POSIX threads that's why timers do not work for me. Tried to create
threads with cyg_lwip_thread_new() but only first thread was
started... Tried to rewrite cyg_lwip_thread_new() to create POSIX
threads instead, but also no luck... The only way I was able to start
all the threads was locking task scheduler before creating and
unlocking after all threads are created. Just thinking what to do
best: continue with modifying cyg_lwip_thread_new() or just get rid of
message queues.

WBR, Alexander

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