On Thu, 4 Jan 2024 14:17:48 GMT, Nir Lisker <nlis...@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). > > modules/javafx.graphics/src/main/java/javafx/css/SimpleSelector.java line 364: > >> 362: return false; >> 363: } >> 364: if >> (this.selectorStyleClassNames.equals(other.selectorStyleClassNames) == >> false) { > > Maybe replace the `==false` with `!`. I've kept the style the same, there is another line like this just below it. Don't like it either personally :) > modules/javafx.graphics/src/main/java/javafx/css/SimpleSelector.java line 383: > >> 381: hash = (id != null) ? 31 * (hash + id.hashCode()) : 0; >> 382: hash = 31 * (hash + pseudoClassState.hashCode()); >> 383: return hash; > > Is it worth caching the hash code for this class? I put a debug print in to this method, and then started JFXCentral application (which is quite big) -- it's never called, so doesn't look like it is used anywhere. Selectors are most often stored in `List`s, didn't find any `Map`s or `Set`s that use it as a key. ------------- PR Review Comment: https://git.openjdk.org/jfx/pull/1316#discussion_r1442407347 PR Review Comment: https://git.openjdk.org/jfx/pull/1316#discussion_r1442406830