[svn.haxx.se] · SVN Dev · SVN Users · SVN Org · TSVN Dev · TSVN Users · Subclipse Dev · Subclipse Users · this month's index

Caching text-size in the entries file

From: Erik Huelsmann <ehuels_at_gmail.com>
Date: 2006-09-25 23:48:56 CEST

I started working on a patch to record the size of the (unedited)
working copy file in the entries file. Using 1 stat() call and this
value, we can detect whether the working copy file has changed,
without the need to detranslate.

This change can get us 2 things:

 - Gain some independence from mtimes: A file which changed in size
clearly has changes, even if the mtimes stay the same
 - Gain in performance in case there are translation-influencing
properties in the game: currently, to establish 'changedness' of the
wc file, libsvn_wc needs to detranslate it to compare to the

These numbers is what I got from a (rudimentary implemented) patch for
'svn status' (in 2 runs):

with keyword props

          old new
run 1 1.8 0.1
run 2 1.2 0.1

without keyword props

          old new
run 1 >0.1 ~0.1
run 2 >0.1 ~0.1

Given these numbers, I thought to implement the feature as follows:

A new field (text-size) will be added to the svn_wc_entry_t structure.
If this field contains a 0 (nul) value, the text-size cache is unused.
Any other value means the working copy file size was originally that

The value of the 'text-size' field will be kept up to date as follows:

- all committed entries will have their text-size cached
- all locally unmodified updated entries will have their text-size cached
- all locally modified updated entries will have their text-size field
set to 0 (nul)
- moved and copied items have their entire entry copied (including the
text-size value)
- reverted items will have their text-size reset to the wc file size
after revert

This change will mean:

- That we will be marking files which have edited keyword values as
modified (we currently don't: we detranslate, making those changes
- That we will be marking files with changed sizes as modified - even
if the mtime hasn't changed - which we currently don't (they show up
as unmodified)
- We will gain 'svn status' speed with many changed files and
svn:keywords (but no extra stat() calls for the case of where no files
- We gain some independence from mtimes




To unsubscribe, e-mail: dev-unsubscribe@subversion.tigris.org
For additional commands, e-mail: dev-help@subversion.tigris.org
Received on Mon Sep 25 23:49:38 2006

This is an archived mail posted to the Subversion Dev mailing list.

This site is subject to the Apache Privacy Policy and the Apache Public Forum Archive Policy.