[1/3] gen_compile_commands: parse only the first line of .*.cmd files
diff mbox series

Message ID 20200812173958.2307251-2-masahiroy@kernel.org
State New
Headers show
Series
  • kbuild: clang-tidy
Related show

Commit Message

Masahiro Yamada Aug. 12, 2020, 5:39 p.m. UTC
After the allmodconfig build, this script takes about 5 sec on my
machine. Most of the run-time is consumed for needless regex matching.

We know the format of .*.cmd file; the first line is the build command.
There is no need to parse the remaining.

With this optimization, now it runs in about 1 sec with the allmodconfig
build.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
---

 scripts/gen_compile_commands.py | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

Comments

Nick Desaulniers Aug. 12, 2020, 9:52 p.m. UTC | #1
On Wed, Aug 12, 2020 at 10:40 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> After the allmodconfig build, this script takes about 5 sec on my
> machine. Most of the run-time is consumed for needless regex matching.
>
> We know the format of .*.cmd file; the first line is the build command.
> There is no need to parse the remaining.
>
> With this optimization, now it runs in about 1 sec with the allmodconfig
> build.
>
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Before your patch, my x86_64 allmodconfig:
$ /usr/bin/time -v ./scripts/gen_compile_commands.py
...
        Elapsed (wall clock) time (h:mm:ss or m:ss): 0:08.35
...
After:
        Elapsed (wall clock) time (h:mm:ss or m:ss): 0:02.10

So it's a nice speedup.
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
small nit below:

> ---
>
>  scripts/gen_compile_commands.py | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/scripts/gen_compile_commands.py b/scripts/gen_compile_commands.py
> index c458696ef3a7..19c7338740e7 100755
> --- a/scripts/gen_compile_commands.py
> +++ b/scripts/gen_compile_commands.py
> @@ -125,11 +125,9 @@ def main():
>              filepath = os.path.join(dirpath, filename)
>
>              with open(filepath, 'rt') as f:
> -                for line in f:
> -                    result = line_matcher.match(line)
> -                    if not result:
> -                        continue
> -
> +                line = f.readline()
> +                result = line_matcher.match(line)

If `line` is not referenced beyond the following statement, consider
combining the two statement into one:
result = line_matcher.match(f.readline())

> +                if result:
>                      try:
>                          entry = process_line(directory, dirpath,
>                                               result.group(1), result.group(2))
> --
> 2.25.1
>

Patch
diff mbox series

diff --git a/scripts/gen_compile_commands.py b/scripts/gen_compile_commands.py
index c458696ef3a7..19c7338740e7 100755
--- a/scripts/gen_compile_commands.py
+++ b/scripts/gen_compile_commands.py
@@ -125,11 +125,9 @@  def main():
             filepath = os.path.join(dirpath, filename)
 
             with open(filepath, 'rt') as f:
-                for line in f:
-                    result = line_matcher.match(line)
-                    if not result:
-                        continue
-
+                line = f.readline()
+                result = line_matcher.match(line)
+                if result:
                     try:
                         entry = process_line(directory, dirpath,
                                              result.group(1), result.group(2))