From: Matt Mackall Date: Mon, 16 May 2005 01:12:09 GMT Subject: Re: Mercurial 0.4e vs git network pull Message-ID: <20050516011209.GM5914@waste.org> In-Reply-To: <428793A1.5070004@pobox.com> On Sun, May 15, 2005 at 02:23:29PM -0400, Jeff Garzik wrote: > Matt Mackall wrote: > >On Sun, May 15, 2005 at 04:22:19AM -0700, Adam J. Richter wrote: > > > >>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 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. > > > > > >You can't do pipelining if you can't look ahead far enough to fill the > >pipe. > > Even if you cannot fill a pipeline, HTTP/1.1 is sufficiently useful > simply by removing the per-request connection overhead. Sure. It cuts round trips by a factor of 2. But that's just about all it does. Mercurial already does: - approximately O(log(new changesets)) requests/data to find new changesets - one request to get an entire changegroup (set of all new changesets), which comes back all nicely pipelined and sorted by file - delta transfer In "dumb http" mode, ie what's been there since about day three, it can do: - one request (size proportional to total number of changesets) to find new changesets - approximately two requests per changed file to pull all deltas (vs request per file revision) - delta transfer -- Mathematics is the supreme nostalgia of our time.