On Thu, 4 Jan 2024 12:21:15 GMT, John Hendrikx <jhendr...@openjdk.org> wrote:
> Improves performance of selector matching in the CSS subsystem. This is done > by using custom set implementation which are highly optimized for the most > common cases where the number of selectors is small (most commonly 1 or 2). > It also should be more memory efficient for medium sized and large > applications which have many style names defined in various CSS files. > > Due to the optimization, the concept of `StyleClass`, which was only > introduced to assign a fixed bit index for each unique style class name > encountered, is no longer needed. This is because style classes are no longer > stored in a `BitSet` which required a fixed index per encountered style class. > > The performance improvements are the result of several factors: > - Less memory use when only very few style class names are used in selectors > and styles from a large pool of potential styles (a `BitSet` for potentially > 1000 different style names needed 1000 bits (worst case) as it was not > sparse). > - Specialized sets for small number of elements (0, 1, 2, 3-9 and 10+) > - Specialized sets are append only (reduces code paths) and can be made read > only without requiring a wrapper > - Iterator creation is avoided when doing `containsAll` check thanks to the > inverse function `isSuperSetOf` > - Avoids making a copy of the list of style class names to compare (to > convert them to `StyleClass` and put them into a `Set`) -- this copy could > not be cached and was always discarded immediately after... > > The overall performance was tested using the JFXCentral application which > displays about 800 nodes on its start page with about 1000 styles in various > style sheets (and which allows to refresh this page easily). > > On JavaFX 20, the fastest refresh speed was 121 ms on my machine. With the > improvements in this PR, the fastest refresh had become 89 ms. The speed > improvement is the result of a 30% faster `Scene#doCSSPass`, which takes up > the bulk of the time to refresh the JFXCentral main page (about 100 ms before > vs 70 ms after the change). This pull request has now been integrated. Changeset: b08d7bbf Author: John Hendrikx <jhendr...@openjdk.org> URL: https://git.openjdk.org/jfx/commit/b08d7bbf83057c83cfde71592869db5aa4efff8e Stats: 1112 lines in 8 files changed: 868 ins; 201 del; 43 mod 8322964: Optimize performance of CSS selector matching Reviewed-by: angorya, mstrauss, mhanl, kcr ------------- PR: https://git.openjdk.org/jfx/pull/1316
