Re: Network compatibility and performance

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linux-os (Dick Johnson) wrote:

No it will return FAIL (-1) or an error and 0 (the bottom of the procedure)
if the whole things went. It is mandatory that the whole thing goes
so this procedure should handle any intermediate actions.

I see..I missed that part.

Upon your advice, I may try to add select() although, on a write it
seems to be putting in user-space something that used to be handled
quite well in the kernel. I don't think the user should really care
about the kernel internals, whether or not the kernel happens to have
a buffer available.

Since you put it in non-blocking mode, you need the select() to throttle
unless you want to busy spin.  Whether you should have to actually put
in in non-blocking mode or not is a different question.

I have no idea why you need to add the MIN() logic..and that seems like
something that should not be required.


It seems that some code 'thinks' that a large buffer of data is
an error and won't even try to send some anymore.

I have seen a problem where I can repeatedly hang a TCP connection
when running at high speed.  The tx queue is full or mostly full, and
on the wire I only see 200kpps of duplicate acks.  Can't reproduce it
with anything other than my big complicated proprietary app, so it
remains unfixed.

I am not sure if this is related to what you see or not..but could you
check to see if there is lots of acks on the wire when this hang happens?

Even 112kbps sucks on a decent network.  What is the speed of your
network, what protocol are you using, if tcp, what is the latency
of your network?



The network is a single wire about 8 feet long, connecting Intel gigibit
links on two identical computers (crossover cable). This link is TCP.
For high-speed data, I use UDP and I get a higher throughput because
there is no handshake. Thew latency is the latency of Linux. BTW, it's
only a gigaBIT link, you can divide that by 8 for gigabytes. I don't
know the actual bit-rate on the wires, if we assume 1GHz, the byte-rate
is only 125,000 bytes per second. Being able to use 89.6 percent of
that isn't bad at all.

You must be meaning to add a few more zeros to that number.  If you
are getting ~125,000,000 Bytes per second then you are doing OK.

Ben

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