linux-kernel - Re: to many sockets ?

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Message-ID: <4524B0E9.8010005@web.de>
Date:	Thu, 05 Oct 2006 09:14:49 +0200
From:	Markus Wenke <M.Wenke@....de>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
CC:	linux-kernel@...r.kernel.org
Subject: Re: to many sockets ?

Alan Cox schrieb:
> Ar Mer, 2006-10-04 am 17:03 +0200, ysgrifennodd Markus Wenke:
>   
>> Hi,
>>
>> I wrote a program which handles incomming sockets asynchron.
>> It can handle up to 140000 connections simultaneously while every 
>> connection send some bytes in both directions continuously.
>>     
>
> Armwavingly 64K x 2 per socket worst case for non tcp windowed buffering
>
> 128K per socket x 140000 connections
>
> 8750MB of RAM
>
> plus other overhead
>
> Assuming you kept the socket buffer limit to 64K by setting it or
> disabling window scaling you'd want a about 10GB of RAM for the sockets,
> buffering and resources. With tcp windows you'd need more.
The default values of my system are:
SO_SNDBUF = 16384
SO_RCVBUF = 87380

> If your data rates are always low, or the link is low latency you could
> set the send/receive socket buffer for each connection via setsockopt
> down to say 8K and come out needing perhaps 1GB or so instead.
>
I tried the same scenario with SO_SNDBUF = SO_RCVBUF = 8k, so that the 
max memory is ca. 2G
and the oom-killer kills my application at the same time (at 140000 
connections).

I can not see in the messages that the system is out of memory,
there is also no swap space used

You can download my /var/log/messages at 
http://hemaho.mine.nu/~biber/messages

May you can give me a hint which line/value in the log shows me,
that the system is out of memory?


Thanks in advance

Markus Wenke

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