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RE: [lwip-users] Slow response times in Microblaze Webserver example

From: jcr_alr
Subject: RE: [lwip-users] Slow response times in Microblaze Webserver example
Date: Tue, 19 Sep 2006 15:07:28 -0300
User-agent: Internet Messaging Program (IMP) 3.1

Hi Ed,

Thanks for fast response.

I removed the xil_printf messages and turned off LWIP_DEBUG. The Ping time 
dropped from 215 to 16 millisecs.

However when I run the GET request the time spent in the read function is still 
2820 millisecs except for the very first time when both the client and server 
programs are loaded and run, then the time is 26 millisecs. Restarting either 
the client or server without restarting the other still results in the long 
delay time. The other lwIP functions called by the Webserver code(eg accept, 
write) seem to be fast.

Without the RS232 messages, the short response time when both server and client 
are restarted seems to be very consistent whereas before the short response 
time was seen only under these conditions but then not always.

Any more thoughts on resolving this problem would be most appreciated.

John Robbins

Quoting "Pisano, Edward A" <address@hidden>:

> Hi John,
> I had seen similar slow response with the WebServer example.  It turned
> out to be the debug output messages.  The RS-232 output has a
> significant slowing effect on lwIP.  In my case, ping replies were
> taking 1700ms to 3400ms on  the Spartan 3E.  I turned off LWIP_DEBUG and
> commented out my own xil_print() statements.  Ping replies quickly
> dropped to 17ms-25ms.
> Regards,
> Ed
> -----Original Message-----
> From: address@hidden
> [mailto:address@hidden On Behalf Of
> address@hidden
> Sent: Tuesday, September 19, 2006 5:47 AM
> To: address@hidden
> Subject: [lwip-users] Slow response times in Microblaze Webserver
> example
> Dear All,
> I have been testing a program modified from the Webserver example for
> the 
> Xilinx Spartan3e Starter Kit. A client application on a PC connected to
> the 
> board via a crossover cable issues a GET command, to which the server
> should 
> respond with a short string, about 50 bytes. 
> The problem that I am finding is that, although the response is
> occasionally 
> very fast, 99% of the time the response may take several seconds. Since
> my 
> eventual application is a fairly fast data acquisition requirement, this
> is a 
> problem.
> To debug this, I first removed the mfs part of the Webserver example,
> then 
> added GPIO calls to the LEDs before and after the read function in 
> processConnection. Using an Ant8 logic analyser, I found that the time
> needed 
> in this function was very occasionally 30 - 40 millisecs but almost
> always 
> around 2900 millisecs.
> Using gdb, I traced the delay to the call in netconn_recv() to
> sys_mbox_fetch() 
> which blocks for 3 seconds, then all the rest of code executes as
> expected. The 
> fast response seems only to occur the first time both the client and
> server are 
> run.
> In XPS I selected the debug output option, set the rs232 speed to 115kbs
> and 
> directed the output to a file. 
> During the block period the system appears to emit at least 
> six  "tcp_slowtmr:procssing active pcb messages" interspersed with some
> timeout 
> messages.
> In case I was doing something wrong in the client code, I used the same
> program 
> to talk to a Netburner card, issuing the same response to a GET request.
> The 
> delays were of the order of a few millisecs.
> So I am sure I am doing something stupid in the server code and would
> really 
> appreciate any help.
> JOhn Robbins.
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