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name-rev: generate name strings only if they are better

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Leave setting the tip_name member of struct rev_name to callers of
create_or_update_name().  This avoids allocations for names that are
rejected by that function.  Here's how this affects the runtime when
working with a fresh clone of Git's own repository; performance numbers
by hyperfine before:

Benchmark #1: ./git -C ../git-pristine/ name-rev --all
  Time (mean ± σ):     437.8 ms ±   4.0 ms    [User: 422.5 ms, System: 15.2 ms]
  Range (min … max):   432.8 ms … 446.3 ms    10 runs

... and with this patch:

Benchmark #1: ./git -C ../git-pristine/ name-rev --all
  Time (mean ± σ):     408.5 ms ±   1.4 ms    [User: 387.2 ms, System: 21.2 ms]
  Range (min … max):   407.1 ms … 411.7 ms    10 runs

Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
René Scharfe 2020-02-04 22:25:34 +01:00 committed by Junio C Hamano
parent 1c56fc2084
commit 977dc1912b
1 changed files with 19 additions and 18 deletions
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37
builtin/name-rev.c
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@ -81,7 +81,6 @@ static int is_better_name(struct rev_name *name,
}
static struct rev_name *create_or_update_name(struct commit *commit,
const char *tip_name,
timestamp_t taggerdate,
int generation, int distance,
int from_tag)
@ -92,7 +91,6 @@ static struct rev_name *create_or_update_name(struct commit *commit,
!is_better_name(name, taggerdate, distance, from_tag))
return NULL;
name->tip_name = tip_name;
name->taggerdate = taggerdate;
name->generation = generation;
name->distance = distance;
@ -130,22 +128,20 @@ static void name_rev(struct commit *start_commit,
struct commit *commit;
struct commit **parents_to_queue = NULL;
size_t parents_to_queue_nr, parents_to_queue_alloc = 0;
char *to_free = NULL;
struct rev_name *start_name;
parse_commit(start_commit);
if (start_commit->date < cutoff)
return;
if (deref)
tip_name = to_free = xstrfmt("%s^0", tip_name);
else
tip_name = to_free = xstrdup(tip_name);
if (!create_or_update_name(start_commit, tip_name, taggerdate, 0, 0,
from_tag)) {
free(to_free);
start_name = create_or_update_name(start_commit, taggerdate, 0, 0,
from_tag);
if (!start_name)
return;
}
if (deref)
start_name->tip_name = xstrfmt("%s^0", tip_name);
else
start_name->tip_name = xstrdup(tip_name);
memset(&queue, 0, sizeof(queue)); /* Use the prio_queue as LIFO */
prio_queue_put(&queue, start_commit);
@ -161,7 +157,7 @@ static void name_rev(struct commit *start_commit,
parents;
parents = parents->next, parent_number++) {
struct commit *parent = parents->item;
const char *new_name;
struct rev_name *parent_name;
int generation, distance;
parse_commit(parent);
@ -169,18 +165,23 @@ static void name_rev(struct commit *start_commit,
continue;
if (parent_number > 1) {
new_name = get_parent_name(name, parent_number);
generation = 0;
distance = name->distance + MERGE_TRAVERSAL_WEIGHT;
} else {
new_name = name->tip_name;
generation = name->generation + 1;
distance = name->distance + 1;
}
if (create_or_update_name(parent, new_name, taggerdate,
generation, distance,
from_tag)) {
parent_name = create_or_update_name(parent, taggerdate,
generation,
distance, from_tag);
if (parent_name) {
if (parent_number > 1)
parent_name->tip_name =
get_parent_name(name,
parent_number);
else
parent_name->tip_name = name->tip_name;
ALLOC_GROW(parents_to_queue,
parents_to_queue_nr + 1,
parents_to_queue_alloc);