On Thu, Oct 26, 2017 at 10:41 AM, Joe Perches <joe@xxxxxxxxxxx> wrote: > 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@xxxxxxxxxxx> 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 > One important piece of information is what version of Git you are running, $ git tag --contains origin/ab/pcre-v2 v2.14.0 ... (and the version of pcre, see the numbers) https://git.kernel.org/pub/scm/git/git.git/commit/?id=94da9193a6eb8f1085d611c04ff8bbb4f5ae1e0a
