Re: [PATCH] cat-file: speed up default format

[Patrick Steinhardt <ps@pks.im>]

On Sun, Jun 14, 2026 at 06:28:34PM +0200, René Scharfe wrote:
> eb54a3391b (cat-file: skip expanding default format, 2022-03-15) added
> special handling for the default batch format.  In the meantime it has
> fallen behind the code path for handling arbitrary formats.  Bring it up
> to speed by using the new and more efficient strbuf_add_oid_hex() and
> strbuf_add_uint() instead of strbuf_addf():
> 
> Benchmark 1: ./git_main cat-file --batch-all-objects --batch-check='%(objectname) %(objecttype) %(objectsize)'
>   Time (mean ± σ):      1.051 s ±  0.003 s    [User: 1.027 s, System: 0.023 s]
>   Range (min … max):    1.049 s …  1.058 s    10 runs
> 
> Benchmark 2: ./git_main cat-file --batch-all-objects --batch-check='%(objectname)-%(objecttype)-%(objectsize)'
>   Time (mean ± σ):      1.012 s ±  0.002 s    [User: 0.988 s, System: 0.023 s]
>   Range (min … max):    1.010 s …  1.018 s    10 runs
> 
> Benchmark 3: ./git cat-file --batch-all-objects --batch-check='%(objectname) %(objecttype) %(objectsize)'
>   Time (mean ± σ):     979.0 ms ±   1.1 ms    [User: 954.1 ms, System: 23.2 ms]
>   Range (min … max):   977.7 ms … 980.8 ms    10 runs
> 
> Summary
>   ./git cat-file --batch-all-objects --batch-check='%(objectname) %(objecttype) %(objectsize)' ran
>     1.03 ± 0.00 times faster than ./git_main cat-file --batch-all-objects --batch-check='%(objectname)-%(objecttype)-%(objectsize)'
>     1.07 ± 0.00 times faster than ./git_main cat-file --batch-all-objects --batch-check='%(objectname) %(objecttype) %(objectsize)'

This almost makes me wonder whether it even makes sense to keep around
the handler for the default format. Is a 3% speedup worth the additional
complexity and the need to keep those sites in sync?

> diff --git a/builtin/cat-file.c b/builtin/cat-file.c
> index 2b64f8f733..d7f7895e30 100644
> --- a/builtin/cat-file.c
> +++ b/builtin/cat-file.c
> @@ -461,9 +461,12 @@ static void print_object_or_die(struct batch_options *opt, struct expand_data *d
>  static void print_default_format(struct strbuf *scratch, struct expand_data *data,
>  				 struct batch_options *opt)
>  {
> -	strbuf_addf(scratch, "%s %s %"PRIuMAX"%c", oid_to_hex(&data->oid),
> -		    type_name(data->type),
> -		    (uintmax_t)data->size, opt->output_delim);
> +	strbuf_add_oid_hex(scratch, &data->oid);
> +	strbuf_addch(scratch, ' ');
> +	strbuf_addstr(scratch, type_name(data->type));
> +	strbuf_addch(scratch, ' ');
> +	strbuf_add_uint(scratch, data->size);
> +	strbuf_addch(scratch, opt->output_delim);
>  }

The change itself looks obviously good to me though, thanks!

Patrick