[GitHub] [hadoop] steveloughran commented on a change in pull request #2358: HADOOP-17295 Move dedicated pre-logging statements into existing logg…

[GitBox <gi...@apache.org>]

steveloughran commented on a change in pull request #2358:
URL: https://github.com/apache/hadoop/pull/2358#discussion_r500899509



##########
File path: hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/DefaultContainerExecutor.java
##########
@@ -566,11 +566,10 @@ public void writeLocalWrapperScript(Path launchDst, Path pidFile,
   @Override
   public boolean signalContainer(ContainerSignalContext ctx)
       throws IOException {
-    String user = ctx.getUser();
     String pid = ctx.getPid();
     Signal signal = ctx.getSignal();
     LOG.debug("Sending signal {} to pid {} as user {}",

Review comment:
       unless the debug is guarded, same cost

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File path: hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPServiceActor.java
##########
@@ -486,12 +486,11 @@ DatanodeCommand cacheReport() throws IOException {
 
       cmd = bpNamenode.cacheReport(bpRegistration, bpid, blockIds);
       long sendTime = monotonicNow();
-      long createCost = createTime - startTime;
       long sendCost = sendTime - createTime;
       dn.getMetrics().addCacheReport(sendCost);
       if (LOG.isDebugEnabled()) {
         LOG.debug("CacheReport of " + blockIds.size()
-            + " block(s) took " + createCost + " msecs to generate and "
+            + " block(s) took " + (createTime - startTime) + " msecs to generate and "

Review comment:
       the cost of a subtraction is marginal. Moving that monotonicNow() would be more significant, as if it is using the x86 `RDSTC` call, its a barrier function which blocks all speculative execution until complete




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