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Re: XML and libsvn_wc performance

From: Branko Čibej <brane_at_xbc.nu>
Date: 2003-11-12 03:08:42 CET

Jason Voegele wrote:

>I've been browsing through the issues list looking for things I might be able
>to lend a hand toward, and performance of checkouts has piqued my interest.
>Issues #1429 and #1490 indicate that XML parsing in libsvn_wc has a fairly
>significant impact on performance. What seems to me an obvious (partial)
>solution has not yet been mentioned, perhaps because I am not seeing the
>whole picture, or the solution I'm proposing is too radical a change for this
>stage of Subversion development. What I'm getting at is why use XML for
>the .svn/entries files at all? Why not replace it with a simpler file format
>and a lex/yacc based parser?
Ouch. Let's stay away from lex or yacc, we have enough dependencies as
it is.


>I could fill in further details if there's any interest in changing the
>entries file format, but in the meantime I'd like to have your opinions about
>whether or not this is a reasonable idea. Please share with me your thoughts
>about this before I pursue any further. If this seems like a good option
>I'll try to put together a patch for it within the next couple of days.
I still haven't seen a real analysis of how much time we spend in the
entries parser, relative to the total WC management overhead. If the
parsing is less than 20% of the WC overhead, then it doesn't make sense
to work on this now. Anyway, I don't believe a custom-built parser would
be so much faster than the XML one that it would make a big difference.

Then there's the issue of upgrading the WC to the new format. For some
time we'd have to support both the old and the new formats, and that
would make parsing the entries file actually slower. Heh.

Brane Čibej   <brane_at_xbc.nu>   http://www.xbc.nu/brane/
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Received on Wed Nov 12 03:11:31 2003

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