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Re: [DESIGN] mtime versioning - was: Getting Bug 1256 fixed

From: Julian Foad <julianfoad_at_btopenworld.com>
Date: 2005-11-28 12:25:23 CET

Malcolm Rowe wrote:
> On Mon, Nov 28, 2005 at 09:59:06AM +0100, Ph. Marek wrote:
>
>>- space on harddisk - this is *currently* important! A wc with 1000 files
>> with no properties other than svn:text-time on a 4kB filesystem needs
>> 1000 * 2 * 4k ~ about 8MByte *only for this properties*!
>> Now go to a wc with 100000 files ... and 800M are gone.

You say "800M are gone" as if it's a bad thing, but if the whole WC occupies 10
GB or so then it's trivial.

>> Although matters are progressing on this front.
>
> That's quite significant. Also, files do not typically have properties
> (with the possible exception of svn:eol-style), and there's a fair amount
> of optimisation that's been done lately to improve matters in that case.
> Adding svn:text-time to all files unconditionally would probably be a
> bad idea.

You're both doing "premature optimisation". Concentrate on what would be
functionally desirable, and THEN determine if we need to make any improvementes
in efficiency, and we'll make them. Mention the inefficiency as a caveat,
don't treat it as a show-stopper.

> [Note that the FSFS format has the capability to store properties as
> deltas against earlier versions, but the implementation doesn't currently
> do that, presumably at least partly because properties are considered to
> be things that change infrequently - and so doing so probably wouldn't
> be worth the effort in terms of space saved, and would also mean it

Looks like you got your argument back to front there :-)

> would take longer to reconstruct the properties during a read.]

Premature optimisation again - unless you have measured that speed loss and
found it to be unacceptably large, which I seriously doubt.

- Julian

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Received on Mon Nov 28 12:27:25 2005

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