Mercurial > hg > mercurial-crew-with-dirclash

view comparison.txt @ 2079:ee96ca273f32

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New lazy index code for revlogs. This tunes for large repositories. It does not read the whole index file in one big chunk, but tries to buffer reads in more reasonable chunks instead. Search speeds are improved in two ways. When trying to find a specific sha hash, it searches from the end of the file backward. More recent entries are more likely to be relevant, especially the tip. Also, this can load only the mapping of nodes to revlog index number. Loading the map uses less cpu (no struct.unpack) and much less memory than loading both the map and the index. This cuts down the time for hg tip on the 80,000 changeset kernel repo from 1.8s to 3.69s. Most commands the pull a single rev out of a big index get roughly the same benefit. Commands that read the whole index are not slower.
author mason@suse.com
date Tue, 04 Apr 2006 16:47:12 -0400
parents 2073e5a71008
children
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                    Mercurial      git                     BK (*)
storage             revlog delta   compressed revisions    SCCS weave
storage naming      by filename    by revision hash        by filename
merge               file DAGs      changeset DAG           file DAGs?
consistency         SHA1           SHA1                    CRC
signable?           yes            yes                     no

retrieve file tip   O(1)           O(1)                    O(revs)
add rev             O(1)           O(1)                    O(revs)
find prev file rev  O(1)           O(changesets)           O(revs)
annotate file       O(revs)        O(changesets)           O(revs)
find file changeset O(1)           O(changesets)           ?

checkout            O(files)       O(files)                O(revs)?
commit              O(changes)     O(changes)              ?
                    6 patches/s    6 patches/s             slow
diff working dir    O(changes)     O(changes)              ?
                    < 1s           < 1s                    ?
tree diff revs      O(changes)     O(changes)              ?
                    < 1s           < 1s                    ?
hardlink clone      O(files)       O(revisions)            O(files)

find remote csets   O(log new)     rsync: O(revisions)     ?
                                   git-http: O(changesets)
pull remote csets   O(patch)       O(modified files)       O(patch)

repo growth         O(patch)       O(revisions)            O(patch)
 kernel history     300M           3.5G?                   250M?
lines of code       2500           6500 (+ cogito)         ??

* I've never used BK so this is just guesses