Forum OpenACS Q&A: Re: Should Keepalive be enabled in config.tcl?
For example, Jonathan, I bet your own www.carnageblender.com site, being an online game, has a high percentage of repeat multiple hits from the same user within just a few seconds of each other. In that case, perhaps AOLserver would be substantially more efficient with keepalive turned on. But perhaps not, and it's certainly possible that keepalive could make performance much worse, too... I don't see any way to know one way or another without empirical testing.
I googled briefly for HTTP keepalive performance tuning info. There were at least a few relevent July 2003 and Nov. 2002 threads on the AOLserver list, but mostly I didn't find anything useful. Neither rules of thumb, nor details on how to properly do log analysis and/or load testing to figure out optimum keepalive settings for a given site, web server, and load.
The (now old and outdated?) C10k page barely mentiond HTTP keepalive, but of course has links to all sorts of detailed server scalability info.
This is currently only of academic interest to me as I don't run a high traffic site. But some folks here do... So if you're reading this, please chime in with your HTTP keepalive tuning experience, as it would be best if we could give OpenACS adopters both a reasonable default keepalive setting in config.tcl and an explanation of why or when they might need to change it.