Re: [PATCH v2] cat-file: skip expanding default format

[Taylor Blau <me@ttaylorr.com>]

On Tue, Mar 08, 2022 at 05:00:53PM -0500, Taylor Blau wrote:
> On my copy of git.git., it shaves off around ~7ms that we're spending
> just copying type names back and forth.

...while we're at it, I think we could go a little further and avoid
doing the mark_query phase altogether, by doing something like:

--- 8< ---

diff --git a/builtin/cat-file.c b/builtin/cat-file.c
index ab9a49e13a..4b3cfb9e68 100644
--- a/builtin/cat-file.c
+++ b/builtin/cat-file.c
@@ -542,24 +542,30 @@ static int batch_objects(struct batch_options *opt)
 	int save_warning;
 	int retval = 0;

-	/*
-	 * Expand once with our special mark_query flag, which will prime the
-	 * object_info to be handed to oid_object_info_extended for each
-	 * object.
-	 */
-	memset(&data, 0, sizeof(data));
-	data.mark_query = 1;
-	strbuf_expand(&output,
-		      opt->format ? opt->format : DEFAULT_FORMAT,
-		      expand_format,
-		      &data);
-	data.mark_query = 0;
-	strbuf_release(&output);
 	if (opt->cmdmode)
 		data.split_on_whitespace = 1;

-	if (opt->format && !strcmp(opt->format, DEFAULT_FORMAT))
+	memset(&data, 0, sizeof(data));
+	if (!opt->format || !strcmp(opt->format, DEFAULT_FORMAT)) {
+		data.info.sizep = &data.size;
+		data.info.typep = &data.type;
+
 		opt->format = NULL;
+	} else {
+		/*
+		 * Expand once with our special mark_query flag, which will prime the
+		 * object_info to be handed to oid_object_info_extended for each
+		 * object.
+		 */
+		data.mark_query = 1;
+		strbuf_expand(&output,
+			      opt->format ? opt->format : DEFAULT_FORMAT,
+			      expand_format,
+			      &data);
+		data.mark_query = 0;
+		strbuf_release(&output);
+	}
+
 	/*
 	 * If we are printing out the object, then always fill in the type,
 	 * since we will want to decide whether or not to stream.

--- >8 ---

...but in my experiments it doesn't seem to help much. Or, at least, it
doesn't obviously help, there's too much noise from run to run for me to
see a worthwhile speed-up here.

Thanks,
Taylor