From: Junio C Hamano <gitster@pobox.com>
Date: Wed, 16 Sep 2009 23:15:17 GMT
Subject: Re: [RFC/PATCH v2] fetch: Speed up fetch by rewriting find_non_local_tags
Message-ID: <7veiq6wkfu.fsf@alter.siamese.dyndns.org>
In-Reply-To: <20090916225350.45746.85139.julian@quantumfyre.co.uk>

Julian Phillips <julian@quantumfyre.co.uk> writes:

> When trying to get a list of remote tags to see if we need to fetch
> any we were doing a linear search for the matching tag ref for the
> tag^{} commit entries.  This proves to be incredibly slow for large
> numbers of tags.  Rewrite the function so that we can do lookup in
> string_lists instead.
>
> For a repository with 50000 tags (and just a single commit on a single
> branch), a fetch that does nothing goes from ~ 1m50s to ~4.2s.
>
> Signed-off-by: Julian Phillips <julian@quantumfyre.co.uk>
> ---
>
> Not only does this not require a custom hash table, it is also slightly
> faster than the last version (~4.2s vs ~4.5s).

I am just curious.  How would a "just one item lookbehind" code perform
compared to this one?