|From:||Enrico Murador - Research & Development - CET|
|Subject:||Re: [lwip-users] Pbuf pool size and network interface|
|Date:||Fri, 24 Jun 2011 18:19:26 +0200|
|User-agent:||Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:188.8.131.52) Gecko/20110616 Thunderbird/3.1.11|
This is ok, as my application (luckily!) requires a very small MSS; I have set(1) 500 bytes is a very small window. Please make sure you set it to be at least 2*MSS to avoid very poor TCP performance;
the TCP window as 2 * MSS obtaining a window of about 620 bytes.
Ok, setting enough buffers is ok for me.(2) if you have less than connections*TCP_WND buffer space, then in the worst case of them all sending at once, you would drop data. This shouldn't lead to a deadlock as the other end will retransmit, but (i) it will result in poor performance and (ii) it is rather wasteful of CPU and bandwidth resources as both sides have gone to some effort to send and receive the data, and if it gets dropped that effort is lost. Kieran
Do you now also if I can tell my netif to use (preallocate for DMA) all the PBUF_POOL buffers available?
It seems that no other part of Lwip code allocates PBUF_POOL buffers, and I'm trying to save some memory...
Thank you very much for your support and patience replying all my questions! ;)
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