topic Re: why udp recv slowly in Operating System - OpenVMS

why udp recv slowly

tianbinraindrop — Wed, 18 May 2005 21:36:56 GMT

My openvms's version is 7.3-1.I have a multithread program to receive udp data.I find my program will lost some data when one computer sends 100 frames/second to my server.My server is ds25,and has a 1000M network card.Who can tell me how to fix this problem? Thank you

Re: why udp recv slowly

Karl Rohwedder — Thu, 19 May 2005 00:19:55 GMT

1st advice would be to read the tuning manual at http://h71000.www7.hp.com/doc/732final/documentation/pdf/aa-rn1vb-te.pdf

regards Kalle

Re: why udp recv slowly

Wim Van den Wyngaert — Thu, 19 May 2005 01:11:00 GMT

If you don't like reading, try increasing the buffers with ucx set prot udp/quo.

Make sure that the receiving process is not a low priority process.

Wim

Re: why udp recv slowly

tianbinraindrop — Thu, 19 May 2005 09:38:50 GMT

Thank you very much.I want to know what's mean of "ucx set pro/quo"? Wheater use qio is better than use socket?How much receiver buffer is best?

Re: why udp recv slowly

Ian Miller. — Thu, 19 May 2005 10:45:12 GMT

A bit more information about
"ucx set prot udp/quo"

Display current values
$ TCPIP SHOW PROTOCOL UDP

$ TCPIP SET PROTOCOL UDP/QUOTA=REC:x

To increase receive quota to x

Re: why udp recv slowly

Wim Van den Wyngaert — Thu, 19 May 2005 10:50:22 GMT

Simply start with the receive value you have (default is 9K) and double it, test performance, double it, test until the loss of packets is acceptable or until you notice that it doesn't help.

It may also be a question of quotas. Check if your process is not bouncing with certain limits (sh proc/quo or use ana/sys).

Or do wath Karl instructed.

Wim

Re: why udp recv slowly

tianbinraindrop — Thu, 19 May 2005 19:54:45 GMT

Thank you.I will try!
I want to know whether the efficiency of QIO is better than standard socket?By the way,I want to know how to implement semaphore in openvms 7.3-1?

Re: why udp recv slowly

Uwe Zessin — Fri, 20 May 2005 01:18:04 GMT

Hm. You do understand that UDP is a datagramm service with NO delivery guarantee, whatever you do to try to tune your machine?

If you need a guarateed delivery I am afraid you have to switch to another mechanism or develop one on your own.

Re: why udp recv slowly

tianbinraindrop — Fri, 20 May 2005 06:24:11 GMT

Yes,I know UDP without delivery guarantee,but my network card is 1000M,and I am sure this send rate is not fast,so I want to tune my machine to receive all udp data.

Re: why udp recv slowly

Ian Miller. — Fri, 20 May 2005 07:36:51 GMT

"I want to know whether the efficiency of QIO is better than standard socket?"

I don't think there will be much difference. sockets are layered on QIO

QIO allows asyncronous operation - sockets don't (without doing threads etc)

Re: why udp recv slowly

Antoniov. — Fri, 20 May 2005 08:37:48 GMT

If you have multithread program you could use socket interface so your software is more portable. QIO is not quicker than socket interface.

Antonio Vigliotti

Re: why udp recv slowly

Wim Van den Wyngaert — Mon, 23 May 2005 04:44:53 GMT

100 frames per second doesn't even generate 0.2 MB per second. I would say that your program isn't following (thus the frames are received and the receive buffer is full and frames are lost) or may be the router in between isn't following (and he is dropping the fragments).

Post the output of ucx sho prot
for further analyzing.

Wim