Re: Calling 'select' from emacs_gnutls_pull

[Eli Zaretskii <eliz@gnu.org>]

> From: claudio.bley@gmail.com (Claudio Bley)
> Date: Fri, 22 Feb 2013 12:15:36 +0100
> 
> However, applying the obvious patch:
> 
> --- >8 ---
> --- src/w32.c	Thu Feb 21 14:35:43 2013
> +++ ../build/src/w32.c	Fri Feb 22 08:32:35 2013
> @@ -7837,27 +7837,9 @@
>  
>        err = errno;
>  
> +      /* Translate the WSAEWOULDBLOCK alias EWOULDBLOCK to EAGAIN. */
>        if (err == EWOULDBLOCK)
> -        {
> -          /* Set a small timeout.  */
> -	  timeout = make_emacs_time (1, 0);
> -          FD_ZERO (&fdset);
> -          FD_SET ((int)fd, &fdset);
> -
> -          /* Use select with the timeout to poll the selector.  */
> -          sc = select (fd + 1, &fdset, (SELECT_TYPE *)0, (SELECT_TYPE *)0,
> -                       &timeout, NULL);
> -
> -          if (sc > 0)
> -            continue;  /* Try again.  */
> -
> -          /* Translate the WSAEWOULDBLOCK alias EWOULDBLOCK to EAGAIN.
> -             Also accept select return 0 as an indicator to EAGAIN.  */
> -          if (sc == 0 || errno == EWOULDBLOCK)
> -            err = EAGAIN;
> -          else
> -            err = errno; /* Other errors are just passed on.  */
> -        }
> +        err = EAGAIN;
>  
>        emacs_gnutls_transport_set_errno (process->gnutls_state, err);
>  
> 
> --- >8 ---
> 
> and made a few tests using POP3 and IMAP connections over TLS and
> HTTPS connections. Works good.

That's good news.

> Average for with-select key over 3 runs
> 
> Version Number:   Windows NT 5.1 (Build 2600)
> Exit Time:        1:00 am, Monday, January 1 1601
> Elapsed Time:     0:00:35.208
> Process Time:     0:00:05.822
> System Calls:     659366     
> Context Switches: 138074     
> Page Faults:      61507      
> Bytes Read:       80719977   
> Bytes Written:    320584     
> Bytes Other:      908395     
> 
> 
> Average for without-select key over 3 runs
> 
> Version Number:   Windows NT 5.1 (Build 2600)
> Exit Time:        1:00 am, Monday, January 1 1601
> Elapsed Time:     0:00:33.796
> Process Time:     0:00:06.166
> System Calls:     857893     
> Context Switches: 140154     
> Page Faults:      69061      
> Bytes Read:       99353998   
> Bytes Written:    2017152    
> Bytes Other:      1175082    

The times look comparable, but I'm confused why byte counts are so
much different.  Is there a good explanation to that?

Anyway, AFAIU, your tests indicate that it would be okay to install
the above changes on the development trunk, right?

Thanks for your valuable feedback.