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
