On Thu, 2017-10-26 at 10:45 -0700, Stefan Beller wrote: > 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 v2.10 > ... > > (and the version of pcre, see the numbers) > https://git.kernel.org/pub/scm/git/git.git/commit/?id=94da9193a6eb8f1085d611c04ff8bbb4f5ae1e0a I definitely didn't have that one. I recompiled git latest (with USE_LIBPCRE2) and reran. Here are the results $ git --version git version 2.15.0.rc2.48.g4e40fb3 $ time git grep -P "\bseq_.*%p\W" -- "*.[ch]" | wc -l 112 real 0m0.437s user 0m1.008s sys 0m0.381s So, git grep performance has already been quite successfully improved. Thanks.
