Re: [PATCH] [GSOC] ref-filter: use single strbuf for all output

From: Derrick Stolee <stolee@gmail.com>
Date: Apr 5, 2021, 21:02 UTC
Message-ID: <50fce64e-d3f5-05e6-5e2a-645864211176@gmail.com>
In-Reply-To: <pull.927.git.1617631280402.gitgitgadget@gmail.com>

On 4/5/2021 10:01 AM, ZheNing Hu via GitGitGadget wrote:

Show 6 quoted lines

> From: ZheNing Hu <adlternative@gmail.com>
> 
> When we use `git for-each-ref`, every ref will call
> `show_ref_array_item()` and allocate its own final strbuf
> and error strbuf. Instead, we can provide two single strbuf:
> final_buf and error_buf that get reused for each output.

s/two single strbuf/two buffers/

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> When run it 100 times:
> 
> $ git for-each-ref
> 
> on git.git :
> 
> 3.19s user
> 3.88s system
> 35% cpu
> 20.199 total
> 
> to:
> 
> 2.89s user
> 4.00s system
> 34% cpu
> 19.741 total
> 
> The performance has been slightly improved.

This is a nice amount of time! Perhaps simplify the presentation:

  The performance for 'git for-each-ref' on the Git
  repository itself with X references changes from
  3.2 seconds to 2.9 seconds.

Show 7 quoted lines

> Signed-off-by: ZheNing Hu <adlternative@gmail.com>
> ---
>     [GSOC] ref-filter: use single strbuf for all output
>     
>     This patch learned Jeff King's optimization measures in git
>     cat-file(79ed0a5): using a single strbuf for all objects output Instead
>     of allocating a large number of small strbuf for every object.

This part of the cover letter could be put into the commit message itself. Use the correct formatting, though:

  This approach is similar to the one used by 79ed0a5
  (cat-file: use a single strbuf for all output, 2018-08-14)
  to speed up the cat-file builtin.

I found the code change to be correct. Thanks! -Stolee