RFR: 8359955: Regressions ~7% in several J2DBench in 25-b26

[Sergey Bylokhov]

On Fri, 8 Aug 2025 16:37:36 GMT, Daniel Gredler <dgredler at openjdk.org> wrote:

> Addresses recent slight performance regressions in some J2DBench benchmarks focused on text drawing.
> 
> `CCharToGlyphMapper` and `CompositeGlyphMapper` cache glyph IDs, but after JDK-8353230 they weren't caching glyph IDs for chars which might be affected by the raw / non-raw glyph distinction, since the cached value may not be correct if we ask for a raw glyph ID one time, but a non-raw glyph ID the next time (or vice versa). This caching exception was the reason for the slightly degraded performance (the `CCharToGlyphMapper` behavior was affecting macOS, and the `CompositeGlyphMapper` behavior was affecting some versions of Windows). This change splits the cache in each of these two classes into two caches, one for raw glyph IDs and one for non-raw glyph IDs, so that all glyphs can benefit from caching.
> 
> All of the font tests (`make test TEST="jtreg:test/jdk/java/awt/font"`) pass for me locally with this change on Linux, macOS and Windows.

src/java.desktop/macosx/classes/sun/font/CCharToGlyphMapper.java line 287:

> 285:                 } else if (isIgnorableWhitespace(code) || (isDefaultIgnorable(code) && !raw)) {
> 286:                     values[i] = INVISIBLE_GLYPH_ID;
> 287:                     put(code, INVISIBLE_GLYPH_ID);

Why do we need to change these lines instead of changing "get()" method above to use "this.raw" instead of parameter?

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PR Review Comment: https://git.openjdk.org/jdk/pull/26702#discussion_r2283769930