Comment 2 for bug 762330

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On 05/06/2011 03:26 PM, Dimitrios Apostolou wrote:
> Likewise, 'bzr checkout --lightweight lp:gcc' downloads almost 8GB of
> data while project data is less than 1GB (metadata excluded, since it's
> lightweight).
>
> On the mailing list I got told that lightweight checkouts are not
> intended for network use, but for local checkouts. In that case light
> checkouts should be disabled for network protocols, or at least show a
> big fat warning to the user. It is *very* discomforting for someone to
> try "lightweight" checkout to be faster than heavy operations, only to
> wait 5h-6h without progress percentage being displayed to have a clue
> that it won't finish anytime soon.

The 8GB is a strict bug which has been fixed in bzr 2.4.
https://bugs.launchpad.net/bzr/+bug/737234

You weren't getting a good progress indication because that particular
code path wasn't supposed to be downloading that much data. (It still
downloads enough that we should be doing a progress bar, but it now does
~150MB rather than 8GB.)

The issue was that we have an in-memory cache for particular content,
the GCC tree was large enough to blow-out the cache, so instead of
hitting cache for everything, new requests which push out old content,
and we would re-read all content for every request. We changed the order
of reads to be in-order rather than cross-order, which both improves how
much data is downloaded, and performance across the board.

I certainly apologize that this wasn't fixed sooner. I won't say that
lightweight checkouts are still optimized for network performance, but
8GB was a bug which has been fixed.

John
=:->
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