Hi,
On Thu, 8 Feb 2007, Jeff King wrote:
> In every case there, pcre has either comparable performance, or simply
> blows away glibc.
So I tested this against external grep. For completeness' sake, I tested
these against each other: GNU regex-0.12, Git _without_ external grep
(relies on glibc's regex), Git _with_ external grep ("original"), pcre,
and for good measure, pcre with NO_MMAP=1 (to test if disk access is the
problem).
Here are the numbers:
grep-gnu-regex:
21.41user 1.08system 0:22.52elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+7210minor)pagefaults 0swaps
21.40user 1.06system 0:22.47elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+7209minor)pagefaults 0swaps
21.61user 1.06system 0:22.68elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+7209minor)pagefaults 0swaps
21.30user 1.10system 0:22.48elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+7210minor)pagefaults 0swaps
21.30user 1.08system 0:22.43elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+7209minor)pagefaults 0swaps
grep-no-external-grep:
6.98user 1.17system 0:08.16elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+7120minor)pagefaults 0swaps
7.07user 1.16system 0:08.27elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+7121minor)pagefaults 0swaps
6.98user 1.12system 0:08.11elapsed 100%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+7121minor)pagefaults 0swaps
7.00user 1.18system 0:08.20elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+7121minor)pagefaults 0swaps
grep-original:
0.82user 1.15system 0:01.97elapsed 100%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+7090minor)pagefaults 0swaps
0.94user 1.03system 0:01.97elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+7099minor)pagefaults 0swaps
0.89user 1.07system 0:01.96elapsed 100%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+7092minor)pagefaults 0swaps
0.81user 1.15system 0:01.97elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+7092minor)pagefaults 0swaps
grep-pcre:
4.04user 1.18system 0:05.24elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+7205minor)pagefaults 0swaps
4.16user 1.08system 0:05.25elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+7206minor)pagefaults 0swaps
4.24user 0.98system 0:05.23elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+7206minor)pagefaults 0swaps
4.08user 1.14system 0:05.23elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+7206minor)pagefaults 0swaps
grep-pcre-no-mmap:
4.15user 1.07system 0:05.22elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+7210minor)pagefaults 0swaps
4.01user 1.14system 0:05.17elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+7209minor)pagefaults 0swaps
3.94user 1.18system 0:05.14elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+7210minor)pagefaults 0swaps
4.11user 1.06system 0:05.18elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+7210minor)pagefaults 0swaps
BTW this was "git grep Lin.*valds" on linux-2.6, just updated.
The first test was run 5 times instead of 4 to make sure it is hot cache.
This is on a dual 1.2GHz 2GB machine.
I cannot really say anything about the pagefaults, so I'll leave that to
the wizards.
Result: external grep wins hands-down. GNU regex loses hands-down. pcre
seems to be better than glibc's regex engine, and gains ever so slightly
when using NO_MMAP.
I ran the same test on a 1GHz 256MB machine which is overloaded, and in
that case, GNU regex is still worst (~55 sec), while glibc and pcre are
equal (glibc slightly slower with ~35 sec, pcre ~34 sec), and external
grep wins (~29 sec). Of course, this is io-bound, but it shows that pcre
uses more memory than glibc.
Ciao,
Dscho
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