From 567c63e7faed9cfdd2cb7fe8cdcb764024f7ebe9 Mon Sep 17 00:00:00 2001
From: Vineet Kumar Maheshwari <vineet.4008@gmail.com>
Date: Tue, 21 Mar 2023 11:43:38 +0530
Subject: [PATCH] Avoid PrioritizedSplitRunner CPU user time overhead

---
 .../executor/PrioritizedSplitRunner.java      | 45 ++++++++++++++++---
 1 file changed, 40 insertions(+), 5 deletions(-)

diff --git a/presto-main/src/main/java/io/prestosql/execution/executor/PrioritizedSplitRunner.java b/presto-main/src/main/java/io/prestosql/execution/executor/PrioritizedSplitRunner.java
index c9ad9c098..e3d8e3bc8 100644
--- a/presto-main/src/main/java/io/prestosql/execution/executor/PrioritizedSplitRunner.java
+++ b/presto-main/src/main/java/io/prestosql/execution/executor/PrioritizedSplitRunner.java
@@ -18,11 +18,13 @@ import com.google.common.util.concurrent.ListenableFuture;
 import com.google.common.util.concurrent.SettableFuture;
 import io.airlift.log.Logger;
 import io.airlift.stats.CounterStat;
-import io.airlift.stats.CpuTimer;
+import io.airlift.stats.CpuTimer.CpuDuration;
 import io.airlift.stats.TimeStat;
 import io.airlift.units.Duration;
 import io.prestosql.execution.SplitRunner;
 
+import java.lang.management.ManagementFactory;
+import java.lang.management.ThreadMXBean;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicLong;
@@ -30,6 +32,7 @@ import java.util.concurrent.atomic.AtomicReference;
 
 import static io.prestosql.operator.Operator.NOT_BLOCKED;
 import static java.lang.String.format;
+import static java.util.Objects.requireNonNull;
 import static java.util.concurrent.TimeUnit.NANOSECONDS;
 
 public class PrioritizedSplitRunner
@@ -159,15 +162,17 @@ public class PrioritizedSplitRunner
 
             waitNanos.getAndAdd(startNanos - lastReady.get());
 
-            CpuTimer timer = new CpuTimer();
+            // Do not collect user vs system components of CPU time since it's more expensive and not used here
+            CpuTimer timer = new CpuTimer(ticker);
             ListenableFuture<?> blocked = split.processFor(SPLIT_RUN_QUANTA);
-            CpuTimer.CpuDuration elapsed = timer.elapsedTime();
+            CpuDuration elapsed = timer.elapsedTime();
 
-            long quantaScheduledNanos = ticker.read() - startNanos;
+            long endNanos = ticker.read();
+            long quantaScheduledNanos = endNanos - startNanos;
             scheduledNanos.addAndGet(quantaScheduledNanos);
 
             priority.set(taskHandle.addScheduledNanos(quantaScheduledNanos));
-            lastRun.set(ticker.read());
+            lastRun.set(endNanos);
 
             if (blocked == NOT_BLOCKED) {
                 unblockedQuantaWallTime.add(elapsed.getWall());
@@ -263,4 +268,34 @@ public class PrioritizedSplitRunner
     {
         return format("Split %-15s-%d", taskHandle.getTaskId(), splitId);
     }
+
+    private static class CpuTimer
+    {
+        private static final ThreadMXBean THREAD_MX_BEAN = ManagementFactory.getThreadMXBean();
+
+        private final Ticker ticker;
+        private final long wallStartTime;
+        private final long cpuStartTime;
+
+        public CpuTimer(Ticker ticker)
+        {
+            this.ticker = requireNonNull(ticker, "ticker is null");
+            this.wallStartTime = ticker.read();
+            this.cpuStartTime = THREAD_MX_BEAN.getCurrentThreadCpuTime();
+        }
+
+        public io.airlift.stats.CpuTimer.CpuDuration elapsedTime()
+        {
+            long currentWallTime = ticker.read();
+            long currentCpuTime = THREAD_MX_BEAN.getCurrentThreadCpuTime();
+            return new io.airlift.stats.CpuTimer.CpuDuration(nanosBetween(wallStartTime, currentWallTime),
+                    nanosBetween(cpuStartTime, currentCpuTime),
+                    null);
+        }
+
+        private static Duration nanosBetween(long start, long end)
+        {
+            return new Duration(Math.abs(end - start), NANOSECONDS);
+        }
+    }
 }
-- 
Gitee