Sergio R. Caprile wrote:
I have this raw api application which tcp_write()s 5 small (~20 bytes)
messages and then checks tcp_sndbuf() to send the biggest possible
chunk, but it ends up having to send a smaller chunk because an internal
queue gets full.
Actually, you have to understand TCP_SND_QUEUELEN to know what this limitation
means:
the snd_queuelen limitation is only a safety check that one pcb does not
consume too
many pbufs when you have multiple pcbs but only a limited number of pbufs.
This limitation is somewhat overridden by the new TCP_OVERSIZE code which
tries
to only create one pbuf per tcp segment *when copying the data*.
When not copying, data, the stack has no choice but to create one pbuf per
tcp_write call. However, this is rather a different amount of memory consumed
(PBUF_RAM or PBUF_POOL vs. PBUF_REF): e.g. you have enough RAM to create 30
PBUF_RAM,
but the PBUF_REF pool holds x100 pbufs.
So in applications where you mix these pbuf types, you might be better off to
just
set TCP_SND_QUEUELEN to a really high value that you never reach and implement
the
check to not enqueue too many pbufs on one connection yourself.
Simon
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