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

["ZheNing Hu via GitGitGadget" <gitgitgadget@gmail.com>]

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.

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.

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.
    
    So ref-filter can learn same thing: use single buffer: final_buf and
    error_buf for all refs output.
    
    Thanks.

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-927%2Fadlternative%2Fref-filter-single-buf-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-927/adlternative/ref-filter-single-buf-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/927

 builtin/for-each-ref.c |  4 +++-
 builtin/tag.c          |  4 +++-
 ref-filter.c           | 21 ++++++++++++---------
 ref-filter.h           |  5 ++++-
 4 files changed, 22 insertions(+), 12 deletions(-)

diff --git a/builtin/for-each-ref.c b/builtin/for-each-ref.c
index cb9c81a04606..9dc41f48bfa0 100644
--- a/builtin/for-each-ref.c
+++ b/builtin/for-each-ref.c
@@ -22,6 +22,8 @@ int cmd_for_each_ref(int argc, const char **argv, const char *prefix)
 	struct ref_array array;
 	struct ref_filter filter;
 	struct ref_format format = REF_FORMAT_INIT;
+	struct strbuf final_buf = STRBUF_INIT;
+	struct strbuf error_buf = STRBUF_INIT;
 
 	struct option opts[] = {
 		OPT_BIT('s', "shell", &format.quote_style,
@@ -81,7 +83,7 @@ int cmd_for_each_ref(int argc, const char **argv, const char *prefix)
 	if (!maxcount || array.nr < maxcount)
 		maxcount = array.nr;
 	for (i = 0; i < maxcount; i++)
-		show_ref_array_item(array.items[i], &format);
+		show_ref_array_item(array.items[i], &format, &final_buf, &error_buf);
 	ref_array_clear(&array);
 	return 0;
 }
diff --git a/builtin/tag.c b/builtin/tag.c
index d403417b5625..8a38b3e2de34 100644
--- a/builtin/tag.c
+++ b/builtin/tag.c
@@ -39,6 +39,8 @@ static int list_tags(struct ref_filter *filter, struct ref_sorting *sorting,
 		     struct ref_format *format)
 {
 	struct ref_array array;
+	struct strbuf final_buf = STRBUF_INIT;
+	struct strbuf error_buf = STRBUF_INIT;
 	char *to_free = NULL;
 	int i;
 
@@ -64,7 +66,7 @@ static int list_tags(struct ref_filter *filter, struct ref_sorting *sorting,
 	ref_array_sort(sorting, &array);
 
 	for (i = 0; i < array.nr; i++)
-		show_ref_array_item(array.items[i], format);
+		show_ref_array_item(array.items[i], format, &final_buf, &error_buf);
 	ref_array_clear(&array);
 	free(to_free);
 
diff --git a/ref-filter.c b/ref-filter.c
index f0bd32f71416..51ff6af64ebc 100644
--- a/ref-filter.c
+++ b/ref-filter.c
@@ -2436,16 +2436,16 @@ int format_ref_array_item(struct ref_array_item *info,
 }
 
 void show_ref_array_item(struct ref_array_item *info,
-			 const struct ref_format *format)
+			 const struct ref_format *format,
+			 struct strbuf *final_buf,
+			 struct strbuf *error_buf)
 {
-	struct strbuf final_buf = STRBUF_INIT;
-	struct strbuf error_buf = STRBUF_INIT;
 
-	if (format_ref_array_item(info, format, &final_buf, &error_buf))
-		die("%s", error_buf.buf);
-	fwrite(final_buf.buf, 1, final_buf.len, stdout);
-	strbuf_release(&error_buf);
-	strbuf_release(&final_buf);
+	if (format_ref_array_item(info, format, final_buf, error_buf))
+		die("%s", error_buf->buf);
+	fwrite(final_buf->buf, 1, final_buf->len, stdout);
+	strbuf_reset(error_buf);
+	strbuf_reset(final_buf);
 	putchar('\n');
 }
 
@@ -2453,9 +2453,12 @@ void pretty_print_ref(const char *name, const struct object_id *oid,
 		      const struct ref_format *format)
 {
 	struct ref_array_item *ref_item;
+	struct strbuf final_buf = STRBUF_INIT;
+	struct strbuf error_buf = STRBUF_INIT;
+
 	ref_item = new_ref_array_item(name, oid);
 	ref_item->kind = ref_kind_from_refname(name);
-	show_ref_array_item(ref_item, format);
+	show_ref_array_item(ref_item, format, &final_buf, &error_buf);
 	free_array_item(ref_item);
 }
 
diff --git a/ref-filter.h b/ref-filter.h
index 19ea4c413409..95498c9f4467 100644
--- a/ref-filter.h
+++ b/ref-filter.h
@@ -120,7 +120,10 @@ int format_ref_array_item(struct ref_array_item *info,
 			  struct strbuf *final_buf,
 			  struct strbuf *error_buf);
 /*  Print the ref using the given format and quote_style */
-void show_ref_array_item(struct ref_array_item *info, const struct ref_format *format);
+void show_ref_array_item(struct ref_array_item *info,
+			 const struct ref_format *format,
+			 struct strbuf *final_buf,
+			 struct strbuf *error_buf);
 /*  Parse a single sort specifier and add it to the list */
 void parse_ref_sorting(struct ref_sorting **sorting_tail, const char *atom);
 /*  Callback function for parsing the sort option */

base-commit: 2e36527f23b7f6ae15e6f21ac3b08bf3fed6ee48
-- 
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