Parser bug: Pattern.compile() called per-invocation in GenerationalHeapParser.splitRemarkReferenceWithWeakReferenceSplitBug

[brunoborges]

Describe the bug

GenerationalHeapParser.splitRemarkReferenceWithWeakReferenceSplitBug(GCLogTrace, String) compiles a regex on every call instead of caching it in a static final field. Regex compilation on a hot parse path is pure overhead and shows up clearly in allocation profiling.

parser/src/main/java/com/microsoft/gctoolkit/parser/GenerationalHeapParser.java (line ~1920):

public void splitRemarkReferenceWithWeakReferenceSplitBug(GCLogTrace trace, String line) {
    GCLogTrace remarkTrace = REMARK_CLAUSE.parse(line);
    Pattern durationGroupPattern = Pattern.compile(".* " + PAUSE_TIME);  // recompiled every call
    Matcher matcher = durationGroupPattern.matcher(line);
    ...

Every other Pattern.compile in the parser (e.g. AbstractLogTrace, ParNewSerial, PreUnifiedDiarizer) is correctly a static final constant — this call site is the outlier.

Evidence (JFR settings=profile, ~28s run)

Workload: sample Main parsing a 195 MB JDK8 ParallelGC rolling log (gclogs/rolling/jdk8/aagl_prd/gc.log), -Xmx1500m, G1, Java 25 (GraalVM 25.0.3). ~19,985 MB sampled allocations.

Regex compilation (not matching) is visibly present in the allocation-by-site profile:

Alloc site	Share
java.util.regex.Pattern.compile()	6.83%
java.util.regex.Pattern.RemoveQEQuoting() (called from compile)	6.87%

Compilation should be a one-time startup cost, not ~7% of steady-state allocation.

Expected behavior

Patterns compiled once and reused:

private static final Pattern DURATION_GROUP_PATTERN = Pattern.compile(".* " + PAUSE_TIME);

Additional context

• Audit sibling methods for the same anti-pattern (any in-method Pattern.compile). The confirmed offending line is GenerationalHeapParser:1920.
• The sample log used here is ParallelGC, so this specific CMS-remark method is not the dominant contributor in this run — but the recompile is still incorrect and will hurt on CMS logs.
• Environment: macOS (Darwin 25.5.0, arm64), Java HotSpot 25.0.3+9-LTS (GraalVM), GCToolkit 3.7.1-SNAPSHOT.