Re: grep vs git grep performance?

From: Stefan Beller <sbeller@google.com>
Date: Oct 26, 2017, 16:58 UTC
Message-ID: <CAGZ79ka41NdzNxGAvtVW802088KydKkp3yHx=Z5q3Mc9GGa_+g@mail.gmail.com>
In-Reply-To: <1509030170.10651.59.camel@perches.com>

+ Avar who knows a thing about pcre (I assume the regex compilation
has impact on grep speed)

On Thu, Oct 26, 2017 at 8:02 AM, Joe Perches <joe@perches.com> wrote:

Show 19 quoted lines

> Comparing a cache warm git grep vs command line grep
> shows significant differences in cpu & wall clock.
>
> Any ideas how to improve this?
>
> $ time git grep "\bseq_.*%p\W" | wc -l
> 112
>
> real    0m4.271s
> user    0m15.520s
> sys     0m0.395s
>
> $ time grep -r --include=*.[ch] "\bseq_.*%p\W" * | wc -l
> 112
>
> real    0m1.164s
> user    0m0.847s
> sys     0m0.314s
>

I wonder how much is algorithmic advantage vs coding/micro optimization that we can do.