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146 lines
4.9 KiB
Markdown
146 lines
4.9 KiB
Markdown
These benchmarks are informal and only intended to give us a general sense of
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the benefit Dart Sass could provide relative to other implementations.
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This was tested against:
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* libsass 27437bc and sassc 36eb82e compiled with g++ 4.8.4.
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* Dart Sass 2bda8fa on Dart 1.22.0-dev.10.3 and Node 7.2.0.
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* Ruby Sass e79f5cf on Ruby 2.2.4p230.
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on Ubuntu x64 with Intel Xeon E5-1650 v3 @ 3.50GHz. The Dart Sass
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[application snapshot][] was trained on the `preceding_sparse_extend.scss` file.
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[application snapshot]: https://github.com/dart-lang/sdk/wiki/Snapshots
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# Measurements
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I ran five instances of each configuration and recorded the fastest time.
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## Small Plain CSS
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Running on a file containing 4 instances of `.foo {a: b}`:
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* sassc: 0.006s
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* Dart Sass from source: 0.278s
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* Dart Sass from a script snapshot: 0.206s
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* Dart Sass from an app snapshot: 0.072s
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* Dart Sass on Node.js via dart2js: 0.246s
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* Ruby Sass with a hot cache: 0.130s
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## Large Plain CSS
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Running on a file containing 2^17 instances of `.foo {a: b}`:
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* sassc: 2.178s
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* Dart Sass from source: 2.341s
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* Dart Sass from a script snapshot: 2.291s
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* Dart Sass from an app snapshot: 2.099s
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* Dart Sass on Node.js via dart2js: 5.758s
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* Ruby Sass with a hot cache: 14.484s
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Based on these numbers, Dart Sass from an app snapshot is approximately:
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* identical to libsass
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* 2.7x faster than Dart Sass on Node
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* 6.9x faster than Ruby Sass
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## Preceding Sparse `@extend`
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Running on a file containing `.x {@extend .y}`, 2^17 instances of `.foo {a: b}`,
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and then `.y {a: b}`:
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* sassc: 2.338s
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* Dart Sass from a script snapshot: 2.326s
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* Dart Sass from an app snapshot: 2.123s
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* Dart Sass on Node.js via dart2js: 6.082s
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* Ruby Sass with a hot cache: 22.423s
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Based on these numbers, Dart Sass from an app snapshot is approximately:
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* 1.1x faster than libsass
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* 2.9x faster than Dart Sass on Node
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* 10.6x faster than Ruby Sass
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## Following Sparse `@extend`
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Running on a file containing `.y {a: b}`, 2^17 instances of `.foo {a: b}`,
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and then `.x {@extend .y}`:
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* sassc: 2.363s
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* Dart Sass from a script snapshot: 2.308s
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* Dart Sass from an app snapshot: 2.143s
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* Dart Sass on Node.js via dart2js: 6.045s
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* Ruby Sass with a hot cache: 22.221s
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Based on these numbers, Dart Sass from an app snapshot is approximately:
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* 1.1x faster than libsass
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* 2.8x faster on the Dart VM than on Node
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* 10.4x faster than Ruby Sass
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## Preceding Dense `@extend`
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Running on a file containing `.bar {@extend .foo}` followed by 2^17 instances of
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`.foo {a: b}`:
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* sassc: 6.826s
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* Dart Sass from a script snapshot: 3.324s
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* Dart Sass from an app snapshot: 3.086s
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* Dart Sass on Node.js via dart2js: 12.054s
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* Ruby Sass with a hot cache: 40.193s
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Based on these numbers, Dart Sass from an app snapshot is approximately:
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* 2.2x faster than libsass
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* 3.9x faster on the Dart VM than on Node
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* 13.0x faster than Ruby Sass
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## Following Dense `@extend`
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Running on a file containing 2^17 instances of `.foo {a: b}` followed by
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`.bar {@extend .foo}`:
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* sassc: 6.796s
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* Dart Sass from a script snapshot: 3.751s
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* Dart Sass from an app snapshot: 3.339s
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* Dart Sass on Node.js via dart2js: 11.551s
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* Ruby Sass with a hot cache: 39.603s
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Based on these numbers, Dart Sass is approximately:
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* 2.0x faster than libsass
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* 3.5x faster on the Dart VM than on Node
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* 11.9x faster than Ruby Sass
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# Conclusions
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Based on this (admittedly imperfect and non-representative) data, Dart Sass can
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match the best performance of any Sass implementation. Because it eagerly tracks
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data for `@extend`s, its worst case is when no `@extend`s are present and that
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tracking proves unnecessary. However, even there it matches the speed of the
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pure-C++ LibSass implementation.
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Because of the novel structuring of `@extend`, we see its relative performance
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increase along with the amount of extension. With only one `@extend` it's
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slightly faster than LibSass; with hundreds of thousands, it's vastly faster.
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It's worth noting that Dart Sass implements `@extend` semantics according to
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[issue 1599][1599], while other implementations do not. This certainly simplifies
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the implementation and may explain some of the speed gains. However, even if
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other implementations could be faster, it's still the case that Dart Sass is
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*fast enough*.
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[1599]: https://github.com/sass/sass/issues/1599
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The only place where Dart Sass falls behind LibSass is when processing small
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files—it's difficult for any VM to beat the startup speed of C++. But the app
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snapshot model means that it stays beneath the crucial 100ms limit for trivial
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files, which means it will look effectively instantaneous to humans.
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It's also interesting to note where Dart Sass falls when run on Node.js. It's
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enough slower than the Dart VM that we probably don't want to position Node.js
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as the primary way of running Sass, but it's still substantially faster than
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Ruby. It probably makes sense to distribute Dart Sass through JS channels as an
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low-overhead introduction, and then make it easy for users to upgrade to the
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Dart version later on for more speed.
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