name-rev: put struct rev_name into commit slab

The commit slab commit_rev_name contains a pointer to a struct rev_name, and the actual struct is allocated separatly. Avoid that allocation and pointer indirection by storing the full struct in the commit slab. Use the tip_name member pointer to determine if the returned struct is initialized. Performance in the Linux repository measured with hyperfine before: Benchmark #1: ./git -C ../linux/ name-rev --all Time (mean ± σ): 953.5 ms ± 6.3 ms [User: 901.2 ms, System: 52.1 ms] Range (min … max): 945.2 ms … 968.5 ms 10 runs ... and with this patch: Benchmark #1: ./git -C ../linux/ name-rev --all Time (mean ± σ): 851.0 ms ± 3.1 ms [User: 807.4 ms, System: 43.6 ms] Range (min … max): 846.7 ms … 857.0 ms 10 runs Signed-off-by: René Scharfe <l.s.r@web.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>

René Scharfe committed Feb 4, 2020 at 22:22 UTC f13ca7cef51cc709c645f9da97f09a150bdb2cac

1 file changed +11 -9

builtin/name-rev.c

+11 -9

@@ -24,7 +24,7 @@ struct rev_name {

24 int from_tag;

25 };

27 -define_commit_slab(commit_rev_name, struct rev_name *);

27 +define_commit_slab(commit_rev_name, struct rev_name);

29 static timestamp_t cutoff = TIME_MAX;

30 static struct commit_rev_name rev_names;

@@ -32,11 +32,16 @@ static struct commit_rev_name rev_names;

32 /* How many generations are maximally preferred over _one_ merge traversal? */

33 #define MERGE_TRAVERSAL_WEIGHT 65535

35 +static int is_valid_rev_name(const struct rev_name *name)

36 +{

37 + return name && name->tip_name;

38 +}

39 +

40 static struct rev_name *get_commit_rev_name(const struct commit *commit)

41 {

37 - struct rev_name **slot = commit_rev_name_peek(&rev_names, commit);

42 + struct rev_name *name = commit_rev_name_peek(&rev_names, commit);

39 - return slot ? *slot : NULL;

44 + return is_valid_rev_name(name) ? name : NULL;

45 }

47 static int is_better_name(struct rev_name *name,

@@ -81,15 +86,12 @@ static struct rev_name *create_or_update_name(struct commit *commit,

86 int generation, int distance,

87 int from_tag)

88 {

84 - struct rev_name **slot = commit_rev_name_at(&rev_names, commit);

85 - struct rev_name *name = *slot;

89 + struct rev_name *name = commit_rev_name_at(&rev_names, commit);

87 - if (name && !is_better_name(name, taggerdate, distance, from_tag))

91 + if (is_valid_rev_name(name) &&

92 + !is_better_name(name, taggerdate, distance, from_tag))

93 return NULL;

90 - if (!name)

91 - name = *slot = xmalloc(sizeof(*name));

92 -

95 name->tip_name = tip_name;

96 name->taggerdate = taggerdate;

97 name->generation = generation;