Re: grep vs git grep performance?

> On Thu, 2017-10-26 at 09:58 -0700, Stefan Beller wrote:
>> + 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:
>> > 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.
>
> As do I.  I presume this is libpcre related.
>
> For instance, git grep performance is better than grep for:
>
> $ time git grep -w "seq_printf" -- "*.[ch]" | wc -l
> 8609
>
> real    0m0.301s
> user    0m0.548s
> sys     0m0.372s
>
> $ time grep -w -r --include=*.[ch] "seq_printf" * | wc -l
> 8609
>
> real    0m0.706s
> user    0m0.396s
> sys     0m0.309s
>