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List:       sbcl-help
Subject:    Re: [Sbcl-help] Question about sockets
From:       Dmitry Statyvka <dmitry () statyvka ! org ! ua>
Date:       2011-10-31 23:09:34
Message-ID: 87d3dclpw1.fsf () statyvka ! org ! ua
[Download RAW message or body]

>>>>> Philipp Marek writes:

 PM> ...
 >>> * I'm not sure if I understood correct, so I doublecheck: both your
 >>> colleagues Java and Erlang programs use the same Java server as you
 >>> do? (So we know the problem is at the lisp side.)
 >> 
 >> Yes, they all use the same server.
 >> 
 >> It seems that this is not simply an SBCL problem, as I originally
 >> thought.  I ran roughly the same code in ACL and SBCL, and saw the
 >> same slowdown of socket traffic versus reading from a file.
 PM> ...
 >> Some format conversion might well be the issue.  Digging deeper in
 >> this code, which was supposed to be an optimization of an
 >> interchange format that was originally ASCII, shows that the socket
 >> streams are (a) bidirectional (the client sends a message to the
 >> server to say "I'm done.") and (b) bivalent (the client's message is
 >> the string "DONE").  This meant that the socket stream does not
 >> provide any useful information to CL about the information it is
 >> carrying.
 PM> Perhaps the problem is Nagle?

 PM>     http://en.wikipedia.org/wiki/Nagle%27s_algorithm

 PM> If the Lisp side waits for some time before sending the (small)
 PM> ACKs, it might explain the bad throughput.

+1.  OP can also try to pass :nodelay t to usocket:socket-connect if one
is in use...

[...]

 PM> Can you use the sb-posix:setsockopt() function to set TCP_NODELAY
 PM> (http://linux.die.net/man/7/tcp) and sb-posix:write() for putting
 PM> the ACK on the line?

[...]

-- 
Dmitry Statyvka


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