From: Petr Baudis <pasky@ucw.cz>
Date: Sun, 15 May 2005 12:40:42 GMT
Subject: Re: Mercurial 0.4e vs git network pull
Message-ID: <20050515124042.GE13024@pasky.ji.cz>
In-Reply-To: <200505151122.j4FBMJa01073@adam.yggdrasil.com>

Dear diary, on Sun, May 15, 2005 at 01:22:19PM CEST, I got a letter
where "Adam J. Richter" <adam@yggdrasil.com> told me that...
> On Sun, 15 May 2005 10:54:05 +0200, Petr Baudis wrote:
> >Dear diary, on Thu, May 12, 2005 at 10:57:35PM CEST, I got a letter
> >where Matt Mackall <mpm@selenic.com> told me that...
> >> Does this need an HTTP request (and round trip) per object? It appears
> >> to. That's 2200 requests/round trips for my 800 patch benchmark.
> 
> >Yes it does. On the other side, it needs no server-side CGI. But I guess
> >it should be pretty easy to write some kind of server-side CGI streamer,
> >and it would then easily take just a single HTTP request (telling the
> >server the commit ID and receiving back all the objects).
> 
> 	I don't understand what was wrong with Jeff Garzik's previous
> suggestion of using http/1.1 pipelining to coalesce the round trips.
> If you're worried about queuing too many http/1.1 requests, the client
> could adopt a policy of not having more than a certain number of
> requests outstanding or perhaps even making a new http connection
> after a certain number of requests to avoid starving other clients
> when the number of clients doing one of these transfers exceeds the
> number of threads that the http server uses.

The problem is that to fetch a revision tree, you have to

	send request for commit A
	receive commit A
	look at commit A for list of its parents
	send request for the parents
	receive the parents
	look inside for list of its parents
	...

(and same for the trees).

> 	Being able to do without a server side CGI script might
> encourage deployment a bit more, both for security reasons and
> effort of deployment.

You could still use it without the server side CGI script as it is now,
just without the speedups.

-- 
				Petr "Pasky" Baudis
Stuff: http://pasky.or.cz/
C++: an octopus made by nailing extra legs onto a dog. -- Steve Taylor