linux-kernel - Re: [PATCH v2 2/7] docs: kdoc: micro-optimize KernRe

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Message-ID: <87ms9kkfb2.fsf@trenco.lwn.net>
Date: Thu, 03 Jul 2025 17:47:13 -0600
From: Jonathan Corbet <corbet@....net>
To: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
Cc: linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org, Akira Yokosawa
 <akiyks@...il.com>
Subject: Re: [PATCH v2 2/7] docs: kdoc: micro-optimize KernRe

Mauro Carvalho Chehab <mchehab+huawei@...nel.org> writes:

> Em Thu,  3 Jul 2025 12:43:58 -0600
> Jonathan Corbet <corbet@....net> escreveu:
>
>> Rework _add_regex() to avoid doing the lookup twice for the (hopefully
>> common) cache-hit case.
>> 
>> Signed-off-by: Jonathan Corbet <corbet@....net>
>> ---
>>  scripts/lib/kdoc/kdoc_re.py | 7 ++-----
>>  1 file changed, 2 insertions(+), 5 deletions(-)
>> 
>> diff --git a/scripts/lib/kdoc/kdoc_re.py b/scripts/lib/kdoc/kdoc_re.py
>> index e81695b273bf..612223e1e723 100644
>> --- a/scripts/lib/kdoc/kdoc_re.py
>> +++ b/scripts/lib/kdoc/kdoc_re.py
>> @@ -29,12 +29,9 @@ class KernRe:
>>          """
>>          Adds a new regex or re-use it from the cache.
>>          """
>> -
>> -        if string in re_cache:
>> -            self.regex = re_cache[string]
>> -        else:
>> +        self.regex = re_cache.get(string, None)
>
> With get, None is default...
>
>> +        if not self.regex:
>>              self.regex = re.compile(string, flags=flags)
>
> ... yet, as you're using get, better to code it as:
>
> 	self.regex = re_cache.get(string, re.compile(string, flags=flags))

...but that will recompile the regex each time, defeating the purpose of
the cache, no?

Thanks,

jon