mikemccand commented on code in PR #15983:
URL: https://github.com/apache/lucene/pull/15983#discussion_r3147024813
##########
build-tools/build-infra/src/main/java/org/apache/lucene/gradle/plugins/java/ProfileResults.java:
##########
@@ -101,10 +101,16 @@ public static void main(String[] args) throws IOException
{
}
/** true if we care about this event */
- static boolean isInteresting(String mode, RecordedEvent event) {
+ static boolean isInteresting(String mode, RecordedEvent event, boolean
hasCPUTimeSamples) {
String name = event.getEventType().getName();
switch (mode) {
case "cpu":
+ if (hasCPUTimeSamples) {
+ // Prefer jdk.CPUTimeSample (Java 25+, JEP 509): samples by CPU
time, not wall-clock
+ // time, so idle threads (like gradle epoll) are inherently excluded
— no filtering
+ // needed. When available, we skip legacy execution samples to avoid
double-counting.
+ return name.equals("jdk.CPUTimeSample");
+ }
return (name.equals("jdk.ExecutionSample") ||
name.equals("jdk.NativeMethodSample"))
Review Comment:
I think `NativeMethodSample` is also a dup, if CPUTime and wall-clock
sampling are both enabled?
##########
build-tools/build-infra/src/main/java/org/apache/lucene/gradle/plugins/java/ProfileResults.java:
##########
@@ -173,6 +199,11 @@ public static void printReport(
if (count < 1) {
throw new IllegalArgumentException("tests.profile.count must be
positive");
}
+
+ // Pre-scan to detect if CPU-time samples (Java 25+, JEP 509) are
available.
+ // If so, prefer them over legacy execution samples to avoid
double-counting.
+ boolean hasCPUTimeSamples = "cpu".equals(mode) &&
detectCPUTimeSamples(files);
Review Comment:
Could we make this stricter? Throw an exception if we see a mix of
`CPUTime` and legacy events? Lucene (and in general anyone profiling, hmm
except maybe profiler debuggers heh) should only have one sampler enabled at a
time?
##########
gradle/testing/profiling.jfc:
##########
@@ -29,6 +29,11 @@ Collects only execution and method samples at a low interval
<setting name="period">1 ms</setting>
</event>
+ <event name="jdk.CPUTimeSample">
Review Comment:
Could we turn off the old (wall-clock) sampling (`jdk.ExecutionSample`,
`jdk.NativeMethodSample`) and just fully commit to `CPUTime`. In nightly
benchmarks we've found the 1 msec sampling to add non-trivial overhead (I think
~5-7% slower).
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