Re: [Sbcl-devel] [usocket-devel] SBCL data flush problem

[Chun T. (binghe) <bin...@gm...>]

Hi, Robert

Thank you for pointing out this issue.  But I'm not sure if it's appropriate to change the default value of :serve-event in all cases, there should be a reason it's setting to T by default.

I want to forward your mail to SBCL mailing list and see if any others have opinions.  I doubt your proposal change may break other usocket-based networking applications on SBCL. (And I want to know how other Lisps handle this)

Regards,

Chun Tian (binghe)

在 2011-8-4，05:58， Robert Brown 写道：

> I use SBCL on Linux and have noticed a problem when writing
> lots of data to socket streams created with usocket.
> 
> In file backend/sbcl.lisp, the function socket-connect creates a
> stream as follows:
> 
> (setf (socket-stream usocket)
>       (sb-bsd-sockets:socket-make-stream socket
>                                                              :input t
>                                                              :output t
>                                                              :buffering :full
> 
> :element-type element-type))
> 
> If you look at the code for sb-bsd-sockets:socket-make-stream in
> sbcl/contrib/sb-bsd-sockets/sockets.lisp, you'll see that it specifies
> a default value of T for the keyword argument serve-events:
> 
>  (defmethod socket-make-stream ((socket socket)
>                               &key input output
>                               (element-type 'character)
>                               (buffering :full)
>                               (external-format :default)
>                               timeout
>                               auto-close
>                               (serve-events t))
> 
> This means that SBCL streams created by usocket have a true
> serve-events property.  When writing large amounts of data to several
> streams, the kernel will eventually stop accepting data from SBCL.
> When this happens, SBCL either waits for I/O to be possible on
> the file descriptor it's writing to or queues the data to be flushed later.
> Because usocket streams specify serve-events as true, SBCL
> always queues.  Instead, it should wait for I/O to be available and
> write the remaining data to the socket.  That's what serve-events
> equal to NIL gets you.
> 
> Usocket should add
> 
>   :serve-events NIL
> 
> to the call to socket-make-stream.
> 
> bob
> 
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