[gambit-list] Edge triggered I/O with libevent

Marc Feeley feeley at iro.umontreal.ca
Tue Aug 30 23:34:58 EDT 2005

Really neat!  I haven't tried it yet (I'm mostly using Mac OS X for  
development) but it sounds promising.  With this patch, heavily  
loaded web-servers written with Gambit should have much better  


On 19-Aug-05, at 9:54 AM, Adam Langley wrote:

> Gambit uses the select call on POSIX systems to multiplex IO
> operations. This is fine for small numbers of file descriptors, but
> falls apart quickly with large numbers[1].
> libevent[2] is a wrapper library around a number of modern IO
> multiplexing systems (epoll on Linux, kqueue on the BSDs as well as
> poll and select).
> Attached is a patch which converts Gambit to using edge triggered I/O
> with epoll and libevent. This also requires a patch (attached) of
> libevent since the standard distribution doesn't include edge
> triggering support and the upstream appears to be on holiday.
> (epoll is required because I don't have a BSD box on which to develop
> edge triggering support for kqueue)
> This patch (for Gambit) preprocesses away to nothing unless
> --enable-libevent is passed to the configure script. (Note that, since
> this patches the configure.ac script, you'll need to run autoconf to
> regenerate).
> I hope I've not broken anything, but at this stage I've only tested
> that the console and tcp ports work.
> This patch (in the future) should also allow people, who write
> programs which use socket calls directly, to integrate into the main
> event loop at some point.
> Testing is more than welcome and, if you find a form of IO which is
> broken, please email me.
> [1] http://monkey.org/~provos/libevent/libevent-benchmark2.jpg
> [2] http://monkey.org/~provos/libevent/
> -- 
> Adam Langley                                       
> agl at imperialviolet.org
> http://www.imperialviolet.org                       (+44) (0)7906  
> 332512
> PGP: 9113   256A   CC0F   71A6   4C84   5087   CDA5   52DF   2CB6    
> 3D60
> <libevent-1.1a-edge.agl.patch>
> <gambit-4b14-libevent-1-agl.patch>
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