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List:       mercurial
Subject:    Re: Load testing of Mercurial
From:       Matt Mackall <mpm () selenic ! com>
Date:       2013-02-25 21:51:52
Message-ID: 1361829112.11033.72.camel () calx
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On Mon, 2013-02-25 at 15:51 -0500, Greg Ward wrote:
> On 24 February 2013, Matt Mackall said:
> > On Sun, 2013-02-24 at 14:08 +0100, Yuri Mikhailov wrote:
> > > Dear Mercurial community,
> > > 
> > > I am a Software Developer and I have been using Mercurial for a while.
> > > Currently my company is looking for a version control system to use
> > > and we find Mercurial a good candidate for us. But what is important
> > > for us to know is scalability of this VCS. Does anyone performed load
> > > testing of Mercurial? What is the practical maximum number of files
> > > and revisions this system can handle?
> > 
> > The Mozilla repository has ~100k commits and 67k files. We consider this
> > mid-sized.
> > 
> > Netbeans has ~250k commits and ~80k files.
> > 
> > The Facebook repository reportedly has ~400k revisions and ~200k files.
> > This is fairly large.
> 
> ...but you'll need good hardware to handle repos like this. My former
> employer was too cheap to buy decent hardware for developers, so their
> repo -- ~130k commits, 25k files -- felt slow a lot of the time,
> especially when doing a full checkout. Particularly on Windows,
> writing 25,000 files to a spinning hard disk takes a while.

We've identified several types of bottlenecks that can occur on
checkout:

- CPU
- I/O bandwidth
- filesystem lookup overhead
- seek rate/journal flushing

The default branch of Mercurial (future 2.6) can do multi-core checkout
on Unix systems, which does a pretty good job of maxing out CPU and I/O
on Linux and making OS/X performance decent-ish.

Systems like Perforce and SVN are unlikely to even get close running
into these bottlenecks because they usually hit a bottleneck on their
servers or networks first.

-- 
Mathematics is the supreme nostalgia of our time.


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