| commit | 937172b247b20ee5d3bbdf345f72748e42b7460d | [log] [tgz] |
|---|---|---|
| author | Caleb Spare <cespare@gmail.com> | Tue Oct 20 01:37:06 2015 -0700 |
| committer | Russ Cox <rsc@golang.org> | Wed Nov 25 17:26:37 2015 +0000 |
| tree | 27b60b3e4a22ca8e2c12772f1254cd01e8dc28e9 | |
| parent | 3aa755b8fb82c28e55938e040bdead6b7f45ae5a [diff] |
regexp: add Copy method to Regexp This helps users who wish to use separate Regexps in each goroutine to avoid lock contention. Previously they had to parse the expression multiple times to achieve this. I used variants of the included benchmark to evaluate this change. I used the arguments -benchtime 20s -cpu 1,2,4,8,16 on a machine with 16 hardware cores. Comparing a single shared Regexp vs. copied Regexps, we can see that lock contention causes huge slowdowns at higher levels of parallelism. The copied version shows the expected linear speedup. name old time/op new time/op delta MatchParallel 366ns ± 0% 370ns ± 0% +1.09% (p=0.000 n=10+8) MatchParallel-2 324ns ±28% 184ns ± 1% -43.37% (p=0.000 n=10+10) MatchParallel-4 352ns ± 5% 93ns ± 1% -73.70% (p=0.000 n=9+10) MatchParallel-8 480ns ± 3% 46ns ± 0% -90.33% (p=0.000 n=9+8) MatchParallel-16 510ns ± 8% 24ns ± 6% -95.36% (p=0.000 n=10+8) I also compared a modified version of Regexp that has no mutex and a single machine (the "RegexpForSingleGoroutine" rsc mentioned in https://github.com/golang/go/issues/8232#issuecomment-66096128). In this next test, I compared using N copied Regexps vs. N separate RegexpForSingleGoroutines. This shows that, even for this relatively simple regex, avoiding the lock entirely would only buy about 10-12% further improvement. name old time/op new time/op delta MatchParallel 370ns ± 0% 322ns ± 0% -12.97% (p=0.000 n=8+8) MatchParallel-2 184ns ± 1% 162ns ± 1% -11.60% (p=0.000 n=10+10) MatchParallel-4 92.7ns ± 1% 81.1ns ± 2% -12.43% (p=0.000 n=10+10) MatchParallel-8 46.4ns ± 0% 41.8ns ±10% -9.78% (p=0.000 n=8+10) MatchParallel-16 23.7ns ± 6% 20.6ns ± 1% -13.14% (p=0.000 n=8+8) Updates #8232. Change-Id: I15201a080c363d1b44104eafed46d8df5e311902 Reviewed-on: https://go-review.googlesource.com/16110 Reviewed-by: Russ Cox <rsc@golang.org>
Go is an open source programming language that makes it easy to build simple, reliable, and efficient software.
For documentation about how to install and use Go, visit https://golang.org/ or load doc/install-source.html in your web browser.
Our canonical Git repository is located at https://go.googlesource.com/go. There is a mirror of the repository at https://github.com/golang/go.
Go is the work of hundreds of contributors. We appreciate your help!
To contribute, please read the contribution guidelines: https://golang.org/doc/contribute.html
Unless otherwise noted, the Go source files are distributed under the BSD-style license found in the LICENSE file.
If you have just untarred a binary Go distribution, you need to set the environment variable $GOROOT to the full path of the go directory (the one containing this file). You can omit the variable if you unpack it into /usr/local/go, or if you rebuild from sources by running all.bash (see doc/install-source.html). You should also add the Go binary directory $GOROOT/bin to your shell's path.
For example, if you extracted the tar file into $HOME/go, you might put the following in your .profile:
export GOROOT=$HOME/go export PATH=$PATH:$GOROOT/bin
See https://golang.org/doc/install or doc/install.html for more details.