8360817: [ubsan] zDirector select_worker_threads - outside the range of representable values issue

MBaesken · MBaesken · commit 16da81eb439e · 2025-07-30T12:28:14.000Z
Reviewed-by: aboldtch, lucy
diff --git a/src/hotspot/share/gc/z/zDirector.cpp b/src/hotspot/share/gc/z/zDirector.cpp
@@ -556,7 +556,7 @@ static double calculate_young_to_old_worker_ratio(const ZDirectorStats& stats) {
 
   const double old_vs_young_efficiency_ratio = current_old_bytes_freed_per_gc_time / current_young_bytes_freed_per_gc_time;
 
-  return old_vs_young_efficiency_ratio;
+  return MIN2(old_vs_young_efficiency_ratio, (double)ZOldGCThreads);
 }
 
 static bool rule_major_proactive(const ZDirectorStats& stats) {

Original file line number	Diff line number	Diff line change
`@@ -556,7 +556,7 @@ static double calculate_young_to_old_worker_ratio(const ZDirectorStats& stats) {`
`556`	`556`
`557`	`557`	`const double old_vs_young_efficiency_ratio = current_old_bytes_freed_per_gc_time / current_young_bytes_freed_per_gc_time;`
`558`	`558`
`559`		`- return old_vs_young_efficiency_ratio;`
	`559`	`+ return MIN2(old_vs_young_efficiency_ratio, (double)ZOldGCThreads);`
`560`	`560`	`}`
`561`	`561`
`562`	`562`	`static bool rule_major_proactive(const ZDirectorStats& stats) {`