Re: [PATCH] bloom: ignore renames when computing changed paths

From: Philip Oakley <philipoakley@iee.email>
To: Derrick Stolee via GitGitGadget <gitgitgadget@gmail.com>,
	git@vger.kernel.org
Cc: Derrick Stolee <dstolee@microsoft.com>
Subject: Re: [PATCH] bloom: ignore renames when computing changed paths
Date: Wed, 8 Apr 2020 20:13:17 +0100	[thread overview]
Message-ID: <7b23c659-56b4-5ed1-eb66-eb112cbde8a3@iee.email> (raw)
In-Reply-To: <pull.601.git.1586363907252.gitgitgadget@gmail.com>

spelling nit.

On 08/04/2020 17:38, Derrick Stolee via GitGitGadget wrote:
> From: Derrick Stolee <dstolee@microsoft.com>
>
> The changed-path Bloom filters record an entry in the filter for
> every path that was changed. This includes every add and delete,
> regardless of whther a rename was detected. Detecting renames
whether
> causes significant performance issues, but also will trigger
> downloading missing blobs in partial clone.
>
> The simple fix is to disable rename detection when computing a
> changed-path Bloom filter.
>
> Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
> ---
>     bloom: ignore renames when computing changed paths
>     
>     I promised [1] I would adapt the commit that was dropped from
>     gs/commit-graph-path-filter [2] on top of gs/commit-graph-path-filter
>     and jt/avoid-prefetch-when-able-in-diff. However, I noticed that the
>     change was extremely simple and has value without basing it on
>     jt/avoid-prefetch-when-able-in-diff.
>     
>     This change applied to gs/commit-graph-path-filter has obvious CPU time
>     improvements for computing changed-path Bloom filters (that I did not
>     measure). The partial clone improvements require
>     jt/avoid-prefetch-when-able-in-diff to be included, too, but the code
>     does not depend on it at compile time.
>     
>     Thanks, -Stolee
>     
>     [1] 
>     https://lore.kernel.org/git/7de2f54b-8704-a0e1-12aa-0ca9d3d70f6f@gmail.com/
>     [2] 
>     https://lore.kernel.org/git/55824cda89c1dca7756c8c2d831d6e115f4a9ddb.1585528298.git.gitgitgadget@gmail.com/
>
> Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-601%2Fderrickstolee%2Fdiff-and-bloom-filters-v1
> Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-601/derrickstolee/diff-and-bloom-filters-v1
> Pull-Request: https://github.com/gitgitgadget/git/pull/601
>
>  bloom.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/bloom.c b/bloom.c
> index c5b461d1cfe..dd9bab9bbd6 100644
> --- a/bloom.c
> +++ b/bloom.c
> @@ -189,6 +189,7 @@ struct bloom_filter *get_bloom_filter(struct repository *r,
>  
>  	repo_diff_setup(r, &diffopt);
>  	diffopt.flags.recursive = 1;
> +	diffopt.detect_rename = 0;
>  	diffopt.max_changes = max_changes;
>  	diff_setup_done(&diffopt);
>  
>
> base-commit: d5b873c832d832e44523d1d2a9d29afe2b84c84f
Philip