Add mallocTrim command to vmTool

arthas-vmtool/src/main/java/arthas/VmTool.java

@@ -116,4 +116,16 @@ public Class<?>[] getAllLoadedClasses() {
         return getAllLoadedClasses0(Class.class);
     }
 
+    @Override
+    public int mallocTrim() {
+        return mallocTrim0();
+    }
+
+    private static synchronized native int mallocTrim0();
+
+    @Override
+    public boolean mallocStats() {
+        return mallocStats0();
+    }
+    private static synchronized native boolean mallocStats0();
 }

arthas-vmtool/src/main/java/arthas/VmToolMXBean.java

@@ -57,4 +57,14 @@ public interface VmToolMXBean {
      * 获取所有已加载的类
      */
     public Class<?>[] getAllLoadedClasses();
+
+    /**
+     * glibc 释放空闲内存
+     */
+    public int mallocTrim();
+
+    /**
+     * glibc 输出内存状态到应用的 stderr
+     */
+    public boolean mallocStats();
 }

arthas-vmtool/src/main/native/src/jni-library.cpp

@@ -4,6 +4,9 @@
 #include <jvmti.h>
 #include "arthas_VmTool.h" // under target/native/javah/
 
+#ifdef __GLIBC__
+#include <malloc.h>
+#endif
 
 static jvmtiEnv *jvmti;
 static jlong tagCounter = 0;
@@ -204,4 +207,24 @@ JNIEXPORT jobjectArray JNICALL Java_arthas_VmTool_getAllLoadedClasses0
     }
     jvmti->Deallocate(reinterpret_cast<unsigned char *>(classes));
     return array;
-}
+}
+
+extern "C"
+JNIEXPORT jint JNICALL Java_arthas_VmTool_mallocTrim0
+        (JNIEnv *env, jclass thisClass) {
+#ifdef __GLIBC__
+    return ::malloc_trim(0);
+#endif
+    return -1;
+}
+
+extern "C"
+JNIEXPORT jboolean JNICALL Java_arthas_VmTool_mallocStats0
+        (JNIEnv *env, jclass thisClass) {
+#ifdef __GLIBC__
+    ::malloc_stats();
+    return JNI_TRUE;
+#else
+    return JNI_FALSE;
+#endif
+}

arthas-vmtool/src/test/java/arthas/VmToolTest.java

@@ -210,4 +210,16 @@ public void test_interrupt_thread() throws InterruptedException {
         TimeUnit.SECONDS.sleep(5);
         Assert.assertEquals(("interrupted " + interruptMe.getId() + " thread success."), re[0].getMessage());
     }
+
+    @Test
+    public void testMallocTrim() {
+        VmTool vmtool = initVmTool();
+        vmtool.mallocTrim();
+    }
+
+    @Test
+    public void testMallocStats() {
+        VmTool vmtool = initVmTool();
+        vmtool.mallocStats();
+    }
 }

core/src/main/java/com/taobao/arthas/core/command/monitor200/VmToolCommand.java

@@ -56,6 +56,8 @@
         + "  vmtool --action getInstances --classLoaderClass org.springframework.boot.loader.LaunchedURLClassLoader --className org.springframework.context.ApplicationContext\n"
         + "  vmtool --action forceGc\n"
         + "  vmtool --action interruptThread -t 1\n"
+        + "  vmtool --action mallocTrim\n"
+        + "  vmtool --action mallocStats\n"
         + Constants.WIKI + Constants.WIKI_HOME + "vmtool")
 //@formatter:on
 public class VmToolCommand extends AnnotatedCommand {
@@ -157,7 +159,7 @@ public void setThreadId(int threadId) {
     }
 
     public enum VmToolAction {
-        getInstances, forceGc, interruptThread
+        getInstances, forceGc, interruptThread, mallocTrim, mallocStats
     }
 
     @Override
@@ -239,6 +241,18 @@ public void process(final CommandProcess process) {
                 process.end();
 
                 return;
+            } else if (VmToolAction.mallocTrim.equals(action)) {
+                int result = vmToolInstance().mallocTrim();
+                process.write("\n");
+                process.end(result == 1 ? 0 : -1, "mallocTrim result: " +
+                    (result == 1 ? "true" : (result == 0 ? "false" : "not supported")));
+                return;
+            } else if (VmToolAction.mallocStats.equals(action)) {
+                boolean result = vmToolInstance().mallocStats();
+                process.write("\n");
+                process.end(result ? 0 : -1, "mallocStats result: " +
+                    (result ? "true" : "not supported"));
+                return;
             }
 
             process.end();

site/docs/doc/vmtool.md

@@ -97,3 +97,32 @@ thread id 通过`-t`参数指定，可以使用 `thread`命令获取。
 ```bash
 vmtool --action interruptThread -t 1
 ```
+
+## glibc 释放空闲内存
+
+Linux man page: [malloc_trim](https://man7.org/linux/man-pages/man3/malloc_trim.3.html)
+
+```bash
+vmtool --action mallocTrim
+```
+
+## glibc 内存状态
+
+内存状态将会输出到应用的 stderr。Linux man page: [malloc_stats](https://man7.org/linux/man-pages/man3/malloc_stats.3.html)
+
+```bash
+vmtool --action mallocStats
+```
+
+输出到 stderr 的内容如下：
+
+```
+Arena 0:
+system bytes     =     135168
+in use bytes     =      74352
+Total (incl. mmap):
+system bytes     =     135168
+in use bytes     =      74352
+max mmap regions =          0
+max mmap bytes   =          0
+```

site/docs/en/doc/vmtool.md

@@ -97,3 +97,32 @@ The thread id is specified by the `-t` parameter. It can be obtained using the `
 ```bash
 vmtool --action interruptThread -t 1
 ```
+
+## glibc Release Free Memory
+
+Linux man page: [malloc_trim](https://man7.org/linux/man-pages/man3/malloc_trim.3.html)
+
+```bash
+vmtool --action mallocTrim
+```
+
+## glibc Memory Status
+
+The memory status will be output to the application's stderr. Linux man page: [malloc_stats](https://man7.org/linux/man-pages/man3/malloc_stats.3.html)
+
+```bash
+vmtool --action mallocStats
+```
+
+The output to stderr is as follows:
+
+```
+Arena 0:
+system bytes     =     135168
+in use bytes     =      74352
+Total (incl. mmap):
+system bytes     =     135168
+in use bytes     =      74352
+max mmap regions =          0
+max mmap bytes   =          0
+```