Re: [PATCH v3] cat-file: skip expanding default format
- From
Taylor Blau <me@ttaylorr.com>
- Date
- Mar 8, 2022, 22:30 UTC
- Message-ID
- <YifZBEAEqUvFwiEV@nand.local>
- In-Reply-To
- <pull.1221.v3.git.git.1646777327043.gitgitgadget@gmail.com>
On Tue, Mar 08, 2022 at 10:08:46PM +0000, John Cai via GitGitGadget wrote:
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> diff --git a/builtin/cat-file.c b/builtin/cat-file.c
> index 7b3f42950ec..e2edba70b41 100644
> --- a/builtin/cat-file.c
> +++ b/builtin/cat-file.c
> @@ -351,6 +351,13 @@ static void print_object_or_die(struct batch_options *opt, struct expand_data *d
> }
> }
>
> +static int print_default_format(char *buf, int len, struct expand_data *data)
> +{
> + return xsnprintf(buf, len, "%s %s %"PRIuMAX"\n", oid_to_hex(&data->oid),
> + type_name(data->type),
> + (uintmax_t)*data->info.sizep);
> +}Two small nits here. It looks like the indentation on the second and third lines is off a little bit, since we'd typically expect those to be indented to the same margin as the first argument to xsnprintf().
The other is that you're reading data->info.sizep by dereferencing it, but we know that it points to data->size. So I think there it makes sense to just read the value directly out of data->size, though note that you'll still need the cast to uintmax_t since you're formatting it with PRIuMAX.
Show 16 quoted lines
> +
> /*
> * If "pack" is non-NULL, then "offset" is the byte offset within the pack from
> * which the object may be accessed (though note that we may also rely on
> @@ -381,10 +388,16 @@ static void batch_object_write(const char *obj_name,
> }
> }
>
> - strbuf_reset(scratch);
> - strbuf_expand(scratch, opt->format, expand_format, data);
> - strbuf_addch(scratch, '\n');
> - batch_write(opt, scratch->buf, scratch->len);
> + if (!opt->format) {
> + char buf[1024];
> + int len = print_default_format(buf, 1024, data);
> + batch_write(opt, buf, len);Just curious (and apologies if this was discussed earlier and I missed it), but: is there a reason that we have to use a scratch buffer here that is separate from the strbuf we already have allocated?
That would avoid a large-ish stack variable, but it means that the two paths are a little more similar, and can share the batch_write call outside of the if/else statement.
The rest of the changes in this file all look good to me.
Show 9 quoted lines
> diff --git a/t/perf/p1006-cat-file.sh b/t/perf/p1006-cat-file.sh > new file mode 100755 > index 00000000000..e463623f5a3 > --- /dev/null > +++ b/t/perf/p1006-cat-file.sh > @@ -0,0 +1,16 @@ > +#!/bin/sh > + > +test_description='Basic sort performance tests'
Is this description a hold-over from p0071? If so, it may be worth updating here.
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> +test_expect_success 'setup' ' > + git rev-list --all >rla > +' > + > +test_perf 'cat-file --batch-check' ' > + git cat-file --batch-check <rla > +'
We could probably get away with dropping the setup test and using `--batch-all-objects` here. Note that right now you're only printing commit objects, so there would be a slight behavior change from the way the patch is currently written, but it should demonstrate the same performance improvement.
Thanks, Taylor