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blame: remove unnecessary use of get_commit_info() 

When `git blame --color-by-age`, the determine_line_heat() is called to
select how to color the output based on the commit's author date.  It
uses the get_commit_info() to parse the information into a `commit_info`
structure, however, this is actually unnecessary because the
determine_line_heat() caller also does the same.

Instead, let's change the determine_line_heat() to take a `commit_info`
structure and remove the internal call to get_commit_info() thus
cleaning up and optimizing the code path.

Enabling Git's trace2 API in order to record the execution time for
every call to determine_line_heat() function:

   + trace2_region_enter("blame", "determine_line_heat", the_repository);
     determine_line_heat(ent, &default_color);
   + trace2_region_enter("blame", "determine_line_heat", the_repository);

Then, running `git blame` for "kernel/fork.c" in linux.git and summing
all the execution time for every call (around 1.3k calls) resulted in
2.6x faster execution (best out 3):

   git built from 328c109303 (The eighth batch, 2021-02-12) = 42ms
   git built from 328c109303 + this change                  = 16ms

Signed-off-by: Rafael Silva <rafaeloliveira.cs@gmail.com>
Reviewed-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Rafael Silva 2021-02-17 15:54:43 +01:00 committed by Junio C Hamano
parent 59ec22464f
commit 8e16effe97
1 changed files with 3 additions and 5 deletions
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8
builtin/blame.c
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@ -425,13 +425,11 @@ static void setup_default_color_by_age(void)
parse_color_fields("blue,12 month ago,white,1 month ago,red");
}
static void determine_line_heat(struct blame_entry *ent, const char **dest_color)
static void determine_line_heat(struct commit_info *ci, const char **dest_color)
{
int i = 0;
struct commit_info ci;
get_commit_info(ent->suspect->commit, &ci, 1);
while (i < colorfield_nr && ci.author_time > colorfield[i].hop)
while (i < colorfield_nr && ci->author_time > colorfield[i].hop)
i++;
*dest_color = colorfield[i].col;
@ -453,7 +451,7 @@ static void emit_other(struct blame_scoreboard *sb, struct blame_entry *ent, int
cp = blame_nth_line(sb, ent->lno);
if (opt & OUTPUT_SHOW_AGE_WITH_COLOR) {
determine_line_heat(ent, &default_color);
determine_line_heat(&ci, &default_color);
color = default_color;
reset = GIT_COLOR_RESET;
}