Performance: it's not getting better (for me anyway)
Robert Collins
robertc at robertcollins.net
Mon Nov 19 23:34:06 GMT 2007
On Fri, 2007-11-16 at 23:53 -0800, Wichmann, Mats D wrote:
> I don't have any benchmarks but subjectively it feels
> like bazaar is getting slower, rather than faster.
...
> If it matters, our branches are all still knit format,
> we have users that we can't force forward quite yet; but
> last week I tried converting one branch (locally and
> upstream) that nobody else uses to dirstate-tags and it
> didn't get better in any way that I noticed.
dirstate-tags is still knits under the hood.
The pack disk format, which is in 0.92, but is not default (there are
still serious limitations to address before it is ready to recommend to
uninformed users) is significantly faster. I see commits on trees that
size, on my laptop, of about 7 seconds.
Merge commits may be much slower in 0.91 and 0.92, due to a change we
made that seemed like a good idea but turns out to do rather poorly in
some corner cases; fixing the graph.heads() function to not have O(N^2)
repeated index access will reduce this corner case behaviour and
probably make it into a net win on knits to do what we did - less IO
will be involved.
On packs merge commits are still quite a bit slower - the patch I put up
last week seems to be a good short term win there - so if you do lots of
merges you'll suffer quite a bit if you go to packs today, but if you
don't do many merges you'll find packs significantly faster.
The file doc/developers/knitpack.txt contains quite a bit of useful
information about packs and their various tradeoffs (no annotation
cache, more robust against network errors and NFS glitches etc).
Hope this helps,
Rob
--
GPG key available at: <http://www.robertcollins.net/keys.txt>.
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