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Re: Surely 'bzr update' shouldn't be this slow?

From: Óscar Fuentes
Subject: Re: Surely 'bzr update' shouldn't be this slow?
Date: Thu, 07 Jan 2010 14:56:02 +0100
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/23.1.90 (gnu/linux)

Alan Mackenzie <address@hidden> writes:


>> 39 minutes for branching outside the shared repository corresponds to a
>> slow machine. It is 10 minutes on a GNU/Linux 2.4 GHz 64 bits
>> worksation-class machine. Bazaar is no speed daemon, but in this case it
>> has to process more than 200 MB of data (not merely copying it around.)
> I beg your pardon?  My machine is a 1.2 GHz Athlon.  That is NOT a slow
> machine by any measure, except that even faster machines are now
> common.

I think that that is the definition of "slow machine" :-)

> Why does Bazaar need to "process" this data?  It's essentially doing
> copying, with some accompanying administrivia.

It is not copying, and in that case it can't simply copy the data. A
shared repository contains data from all the branches it encloses. When
you branch from it, only the data that belongs to the branch you want
must be transferred.

I don't know why Bazaar does not copy the files under .bzr when you
clone a branch when it is on the same format that the target,
though. A good question for it ml.

> Is it doing heavy number crunching in Python, when it really needs a C
> module, or something like that?

The inner loops are written in C.

> I just did a 'bzr update' on my .../trunk.  It took 23 minutes,
> transferring nearly 200Mb to/from savannah in the process.  This compares
> with all our source files (.c, .h, .el) being ~64Mb.  Could it be that
> 'bzr update' just downloads the whole repository again?  Or has somebody
> else raised this issue on another thread that I've missed?

Yup, that was recently discussed here. It was an exceptional case (I

> There seems to be a substantial mismatch between the assumptions of the
> bzr project and the realities of the Emacs project.  My impression is
> that bzr is so slow as to be barely usable at the moment.

Apart from the 200MB download, do you think that bzr is too slow on your
daily Emacs work? Which operations are too slow for you?

Sometimes I work on a netbook, which maybe is comparable to your 1.2GHz
Athlon on CPU power, and some operations are slow indeed (>20 seconds
for the log of a file.) I raised this on the Bazaar ml, but most people
there think that Bazaar is fast enough and no extensive work is planned
for performance improvements.


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