'bzr branch -r -XXX foo bar' slow for long histories

[John Arbash Meinel]

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Aaron Bentley wrote:
| Robert Collins wrote:
|> On Sun, 2008-03-16 at 14:13 +0000, John Arbash Meinel wrote:
|>> It also has the problem that our KnitPackRepositories don't cache any
|>> parent information (I have a hack for maintaining the
|>> CachingParentsProvider), which means it has to go back to the Index
|>> each
|>> time.
|> The index caches the parents though; and it should not be bisecting on a
|> lookup of a found key.
|
| My experience is that avoiding repeating the same node lookup is a
| significant performance win.
|
| Aaron

Well, introducing the CachingParentsProvider in the first place was an enormous
win for the places I was using it. So I'll have to agree.

Looking at --lsprof, we spend say 12s in _lookup_by... and only about 6s in
_parse_lines. That was for something like 350k calls to _lookup_by and 6k calls
to _parse_lines.

John
=:->
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