8281181: Do not use CPU Shares to compute active processor count

Reviewed-by: dholmes, sgehwolf

src/hotspot/os/linux/cgroupSubsystem_linux.cpp

@@ -495,7 +495,12 @@ int CgroupSubsystem::active_processor_count() {
   cpu_count = limit_count = os::Linux::active_processor_count();
   int quota  = cpu_quota();
   int period = cpu_period();
-  int share  = cpu_shares();
+
+  // It's not a good idea to use cpu_shares() to limit the number
+  // of CPUs used by the JVM. See JDK-8281181.
+  // UseContainerCpuShares and PreferContainerQuotaForCPUCount are
+  // deprecated and will be removed in the next JDK release.
+  int share  = UseContainerCpuShares ? cpu_shares() : -1;
 
   if (quota > -1 && period > 0) {
     quota_count = ceilf((float)quota / (float)period);

src/hotspot/os/linux/globals_linux.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2005, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2005, 2022, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -59,10 +59,14 @@
   product(bool, UseContainerSupport, true,                              \
           "Enable detection and runtime container configuration support") \
                                                                         \
+  product(bool, UseContainerCpuShares, false,                           \
+          "(Deprecated) Include CPU shares in the CPU availability"     \
+          " calculation.")                                              \
+                                                                        \
   product(bool, PreferContainerQuotaForCPUCount, true,                  \
-          "Calculate the container CPU availability based on the value" \
+          "(Deprecated) Calculate the container CPU availability based" \
-          " of quotas (if set), when true. Otherwise, use the CPU"      \
+          " on the value of quotas (if set), when true. Otherwise, use" \
-          " shares value, provided it is less than quota.")             \
+          " the CPU shares value, provided it is less than quota.")     \
                                                                         \
   product(bool, AdjustStackSizeForTLS, false,                           \
           "Increase the thread stack size to include space for glibc "  \

src/hotspot/share/runtime/arguments.cpp

@@ -538,6 +538,8 @@ static SpecialFlag const special_jvm_flags[] = {
   { "UseHeavyMonitors",             JDK_Version::jdk(18), JDK_Version::jdk(19), JDK_Version::jdk(20) },
 #endif
   { "ExtendedDTraceProbes",         JDK_Version::jdk(19), JDK_Version::jdk(20), JDK_Version::jdk(21) },
+  { "UseContainerCpuShares",        JDK_Version::jdk(19), JDK_Version::jdk(20), JDK_Version::jdk(21) },
+  { "PreferContainerQuotaForCPUCount", JDK_Version::jdk(19), JDK_Version::jdk(20), JDK_Version::jdk(21) },
 
   // --- Deprecated alias flags (see also aliased_jvm_flags) - sorted by obsolete_in then expired_in:
   { "DefaultMaxRAMFraction",        JDK_Version::jdk(8),  JDK_Version::undefined(), JDK_Version::undefined() },

test/hotspot/jtreg/containers/cgroup/PlainRead.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2017, 2022, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -50,7 +50,7 @@ public class PlainRead {
     static final String good_value = "(\\d+|-1|-2|Unlimited)";
     static final String bad_value = "(failed)";
 
-    static final String[] variables = {"Memory Limit is:", "CPU Shares is:", "CPU Quota is:", "CPU Period is:", "active_processor_count:"};
+    static final String[] variables = {"Memory Limit is:", "CPU Quota is:", "CPU Period is:", "active_processor_count:"};
 
     static public void isContainer(OutputAnalyzer oa) {
         for (String v: variables) {

test/hotspot/jtreg/containers/docker/TestCPUAwareness.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2017, 2022, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -100,6 +100,11 @@ public class TestCPUAwareness {
         String cpuSetStr = CPUSetsReader.readFromProcStatus("Cpus_allowed_list");
         System.out.println("cpuSetStr = " + cpuSetStr);
 
+        // OLD = use the deprecated -XX:+UseContainerCpuShares flag, which
+        // will be removed in the next JDK release. See JDK-8281181.
+        boolean OLD = true;
+        boolean NEW = false;
+
         if (cpuSetStr == null) {
             System.out.printf("The cpuset test cases are skipped");
         } else {
@@ -108,23 +113,32 @@ public class TestCPUAwareness {
             // Test subset of cpuset with one element
             if (cpuSet.size() >= 1) {
                 String testCpuSet = CPUSetsReader.listToString(cpuSet, 1);
-                testAPCCombo(testCpuSet, 200*1000, 100*1000,   4*1024, true, 1);
+                testAPCCombo(OLD, testCpuSet, 200*1000, 100*1000,   4*1024, true, 1);
+                testAPCCombo(NEW, testCpuSet, 200*1000, 100*1000,   4*1024, true, 1);
             }
 
             // Test subset of cpuset with two elements
             if (cpuSet.size() >= 2) {
                 String testCpuSet = CPUSetsReader.listToString(cpuSet, 2);
-                testAPCCombo(testCpuSet, 200*1000, 100*1000, 4*1024, true, 2);
+                testAPCCombo(OLD, testCpuSet, 200*1000, 100*1000, 4*1024, true, 2);
-                testAPCCombo(testCpuSet, 200*1000, 100*1000, 1023,   true, 2);
+                testAPCCombo(OLD, testCpuSet, 200*1000, 100*1000, 1023,   true, 2);
-                testAPCCombo(testCpuSet, 200*1000, 100*1000, 1023,   false,  1);
+                testAPCCombo(OLD, testCpuSet, 200*1000, 100*1000, 1023,   false,1);
+
+                testAPCCombo(NEW, testCpuSet, 200*1000, 100*1000, 4*1024, true, 2);
+                testAPCCombo(NEW, testCpuSet, 200*1000, 100*1000, 1023,   true, 2);
+                testAPCCombo(NEW, testCpuSet, 200*1000, 100*1000, 1023,   false,2);
             }
 
             // Test subset of cpuset with three elements
             if (cpuSet.size() >= 3) {
                 String testCpuSet = CPUSetsReader.listToString(cpuSet, 3);
-                testAPCCombo(testCpuSet, 100*1000, 100*1000, 2*1024, true, 1);
+                testAPCCombo(OLD, testCpuSet, 100*1000, 100*1000, 2*1024, true, 1);
-                testAPCCombo(testCpuSet, 200*1000, 100*1000, 1023,   true, 2);
+                testAPCCombo(OLD, testCpuSet, 200*1000, 100*1000, 1023,   true, 2);
-                testAPCCombo(testCpuSet, 200*1000, 100*1000, 1023,   false,  1);
+                testAPCCombo(OLD, testCpuSet, 200*1000, 100*1000, 1023,   false,1);
+
+                testAPCCombo(NEW, testCpuSet, 100*1000, 100*1000, 2*1024, true, 1);
+                testAPCCombo(NEW, testCpuSet, 200*1000, 100*1000, 1023,   true, 2);
+                testAPCCombo(NEW, testCpuSet, 200*1000, 100*1000, 1023,   false,2);
             }
         }
     }
@@ -181,8 +195,11 @@ public class TestCPUAwareness {
     }
 
 
-    // Test correctess of automatically selected active processor cound
+    // Test correctess of automatically selected active processor count
-    private static void testAPCCombo(String cpuset, int quota, int period, int shares,
+    // Note: when -XX:+UseContainerCpuShares is removed,
+    // useContainerCpuShares, shares, and usePreferContainerQuotaForCPUCount
+    // should also be removed.
+    private static void testAPCCombo(boolean useContainerCpuShares, String cpuset, int quota, int period, int shares,
                                      boolean usePreferContainerQuotaForCPUCount,
                                      int expectedAPC) throws Exception {
         Common.logNewTestCase("test APC Combo");
@@ -190,6 +207,7 @@ public class TestCPUAwareness {
         System.out.println("quota = " + quota);
         System.out.println("period = " + period);
         System.out.println("shares = " + shares);
+        System.out.println("useContainerCpuShares = " + useContainerCpuShares);
         System.out.println("usePreferContainerQuotaForCPUCount = " + usePreferContainerQuotaForCPUCount);
         System.out.println("expectedAPC = " + expectedAPC);
 
@@ -201,13 +219,15 @@ public class TestCPUAwareness {
             .addDockerOpts("--cpu-quota=" + quota)
             .addDockerOpts("--cpu-shares=" + shares);
 
-        if (!usePreferContainerQuotaForCPUCount) opts.addJavaOpts("-XX:-PreferContainerQuotaForCPUCount");
+        if (useContainerCpuShares) opts.addJavaOpts("-XX:+UseContainerCpuShares");  // deprecated
+        if (!usePreferContainerQuotaForCPUCount) opts.addJavaOpts("-XX:-PreferContainerQuotaForCPUCount");  // deprecated
 
         Common.run(opts)
             .shouldMatch("active_processor_count.*" + expectedAPC);
     }
 
 
+    // Note: when -XX:+UseContainerCpuShares is removed, this test should also be removed.
     private static void testCpuShares(int shares, int expectedAPC) throws Exception {
         Common.logNewTestCase("test cpu shares, shares = " + shares);
         System.out.println("expectedAPC = " + expectedAPC);
@@ -216,6 +236,7 @@ public class TestCPUAwareness {
 
         DockerRunOptions opts = Common.newOpts(imageName)
             .addDockerOpts("--cpu-shares=" + shares);
+        opts.addJavaOpts("-XX:+UseContainerCpuShares"); // deprecated
         OutputAnalyzer out = Common.run(opts);
         // Cgroups v2 needs to do some scaling of raw shares values. Hence,
         // 256 CPU shares come back as 264. Raw value written to cpu.weight

test/hotspot/jtreg/runtime/CommandLine/VMDeprecatedOptions.java

@@ -54,6 +54,8 @@ public class VMDeprecatedOptions {
             {"InitialRAMFraction",        "64"},
             {"TLABStats",                 "false"},
             {"AllowRedefinitionToAddDeleteMethods", "true"},
+            {"UseContainerCpuShares",      "false"},
+            {"PreferContainerQuotaForCPUCount", "true"},
 
             // deprecated alias flags (see also aliased_jvm_flags):
             {"DefaultMaxRAMFraction", "4"},