jvm improve docker container detection and resource configuration usage

background

Java startup normally queries the operating system in order to setup runtime defaults for things such as the number of GC threads and default memory limits.

While in docker container, JVM can’t get the resource limit info.

This problem had been fixed in JDK8:8u191

This article make a test for the new feature

VM info

a linux vm in google cloud, with 6 vCPUS, 20GB memory

Test In VM

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bamboo@privacy:~$ free -g
total used free shared buff/cache available
Mem: 19 6 0 0 13 12
Swap: 0 0 0
bamboo@privacy:~$ cat /proc/cpuinfo| grep "processor"| wc -l
6
bamboo@privacy:~$ java -version
java version "1.8.0_171"
Java(TM) SE Runtime Environment (build 1.8.0_171-b11)
Java HotSpot(TM) 64-Bit Server VM (build 25.171-b11, mixed mode)
bamboo@privacy:~$ java -XX:+PrintFlagsFinal | grep -E 'InitialHeapSize|MaxHeapSize'
uintx InitialHeapSize := 329252864 {product}
uintx MaxHeapSize := 5263851520 {product}
bamboo@privacy:~$ java -XX:+PrintFlagsFinal | grep -E ParallelGCThreads
uintx ParallelGCThreads = 6 {product}

Test in docker container (openjdk:8u181) without resource limit

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bamboo@privacy:~$ docker run -ti openjdk:8u181-jdk
root@c559e42aeae2:/# free -g
total used free shared buff/cache available
Mem: 19 6 0 0 12 12
Swap: 0 0 0
root@c559e42aeae2:/# cat /proc/cpuinfo| grep "processor"| wc -l
6
root@c559e42aeae2:/# java -version
openjdk version "1.8.0_181"
OpenJDK Runtime Environment (build 1.8.0_181-8u181-b13-2~deb9u1-b13)
OpenJDK 64-Bit Server VM (build 25.181-b13, mixed mode)
root@c559e42aeae2:/# java -XX:+PrintFlagsFinal | grep -E 'InitialHeapSize|MaxHeapSize'
uintx InitialHeapSize := 329252864 {product}
uintx MaxHeapSize := 5263851520 {product}
root@c559e42aeae2:/# java -XX:+PrintFlagsFinal | grep -E ParallelGCThreads
uintx ParallelGCThreads = 6 {product}

Test in docker container (openjdk:8u181) with resource limit

8G memory, 2 cpus

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bamboo@privacy:~$ docker run -it --cpus 2 -m 8g openjdk:8u181-jdk bash
root@5d34cdeb3d5c:/#
root@5d34cdeb3d5c:/# free -g
total used free shared buff/cache available
Mem: 19 6 0 0 12 12
Swap: 0 0 0
root@5d34cdeb3d5c:/# cat /proc/cpuinfo| grep "processor"| wc -l
6
root@5d34cdeb3d5c:/# java -version
openjdk version "1.8.0_181"
OpenJDK Runtime Environment (build 1.8.0_181-8u181-b13-2~deb9u1-b13)
OpenJDK 64-Bit Server VM (build 25.181-b13, mixed mode)
root@5d34cdeb3d5c:/# java -XX:+PrintFlagsFinal | grep -E 'InitialHeapSize|MaxHeapSize'
uintx InitialHeapSize := 329252864 {product}
uintx MaxHeapSize := 5263851520 {product}
root@5d34cdeb3d5c:/# java -XX:+PrintFlagsFinal | grep -E ParallelGCThreads
uintx ParallelGCThreads = 6 {product}

Test in docker container (openjdk:8u212) without resource limit

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bamboo@privacy:~$ docker run -ti openjdk:8u212-jdk
root@9fd6c496e060:/# free -g
total used free shared buff/cache available
Mem: 19 6 0 0 12 12
Swap: 0 0 0
root@9fd6c496e060:/# cat /proc/cpuinfo| grep "processor"| wc -l
6
root@9fd6c496e060:/# java -version
openjdk version "1.8.0_212"
OpenJDK Runtime Environment (build 1.8.0_212-b04)
OpenJDK 64-Bit Server VM (build 25.212-b04, mixed mode)
root@9fd6c496e060:/# java -XX:+PrintFlagsFinal | grep -E 'InitialHeapSize|MaxHeapSize'
uintx InitialHeapSize := 329252864 {product}
uintx MaxHeapSize := 5263851520 {product}
root@9fd6c496e060:/# java -XX:+PrintFlagsFinal | grep -E ParallelGCThreads
uintx ParallelGCThreads = 6 {product}

Test in docker container (openjdk:8u212) with resource limit

8G memory, 2 cpus

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bamboo@privacy:~$ docker run -it --cpus 2 -m 8g openjdk:8u212-jdk bash
root@6e90872b448b:/# free -g
total used free shared buff/cache available
Mem: 19 6 0 0 12 12
Swap: 0 0 0
root@6e90872b448b:/# cat /proc/cpuinfo| grep "processor"| wc -l
6
root@6e90872b448b:/# java -version
openjdk version "1.8.0_212"
OpenJDK Runtime Environment (build 1.8.0_212-b04)
OpenJDK 64-Bit Server VM (build 25.212-b04, mixed mode)
root@6e90872b448b:/# java -XX:+PrintFlagsFinal | grep -E 'InitialHeapSize|MaxHeapSize'
uintx InitialHeapSize := 134217728 {product}
uintx MaxHeapSize := 2147483648 {product}
root@6e90872b448b:/# java -XX:+PrintFlagsFinal | grep -E ParallelGCThreads
uintx ParallelGCThreads = 2 {product}

compare table

env\command free -g cat /proc/cpuinfo jvm InitialHeapSize jvm MaxHeapSize jvm ParallelGCThreads
VM 20G 6 329252864 (314M) 5263851520 (4.9G) 6
docker (openjdk:8u181) 20G 6 329252864 5263851520 6
docker (openjdk:8u181) resource limit [cpu:2, memory:8G] 20G 6 329252864 5263851520 6
docker (openjdk:8u212) 20G 6 329252864 5263851520 6
docker (openjdk:8u181) resource limit [cpu:2, memory:8G] 20G 6 134217728 (128M) 2147483648 (2G) 2

conclusion

  • openjdk:8u212 can get the resource limit in docker container

implementation

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 julong os::Linux::available_memory() {
   // values in struct sysinfo are "unsigned long"
   struct sysinfo si;
-  sysinfo(&si);
+  julong avail_mem;
 
-  return (julong)si.freeram * si.mem_unit;
+  if (OSContainer::is_containerized()) {
+    jlong mem_limit, mem_usage;
+    if ((mem_limit = OSContainer::memory_limit_in_bytes()) > 0) {
+      if ((mem_usage = OSContainer::memory_usage_in_bytes()) > 0) {
+        if (mem_limit > mem_usage) {
+          avail_mem = (julong)mem_limit - (julong)mem_usage;
+        } else {
+          avail_mem = 0;
+        }
+        log_trace(os)("available container memory: " JULONG_FORMAT, avail_mem);
+        return avail_mem;
+      } else {
+        log_debug(os,container)("container memory usage call failed: " JLONG_FORMAT, mem_usage);
+      }
+    } else {
+      log_debug(os,container)("container memory unlimited or failed: " JLONG_FORMAT, mem_limit);
+    }
+  }
+
+  sysinfo(&si);
+  avail_mem = (julong)si.freeram * si.mem_unit;
+  log_trace(os)("available memory: " JULONG_FORMAT, avail_mem);
+  return avail_mem;
 }
  
 julong os::physical_memory() {
-  return Linux::physical_memory();
+  if (OSContainer::is_containerized()) {
+    jlong mem_limit;
+    if ((mem_limit = OSContainer::memory_limit_in_bytes()) > 0) {
+      log_trace(os)("total container memory: " JLONG_FORMAT, mem_limit);
+      return (julong)mem_limit; 
+    } else {
+      if (mem_limit == OSCONTAINER_ERROR) {
+        log_debug(os,container)("container memory limit call failed");
+      }
+      if (mem_limit == -1) {
+        log_debug(os,container)("container memory unlimited, using host value");
+      }
+    }
+  }
+
+  jlong phys_mem = Linux::physical_memory();
+  log_trace(os)("total system memory: " JLONG_FORMAT, phys_mem);
+  return phys_mem;
 }

JDK-8146115 : Improve docker container detection and resource configuration usage

jira : https://bugs.java.com/bugdatabase/view_bug.do?bug_id=JDK-8146115

patch : http://cr.openjdk.java.net/~bobv/8146115/webrev.03/open.patch