BoxStore: add Linux-only sysProcMeminfoKb() and sysProcStatusKb()

Author: greenrobot

objectbox-java/src/main/java/io/objectbox/BoxStore.java

@@ -182,6 +182,10 @@ static native void nativeRegisterCustomType(long store, int entityId, int proper
 
     native long nativeValidate(long store, long pageLimit, boolean checkLeafLevel);
 
+    static native long nativeSysProcMeminfoKb(String key);
+
+    static native long nativeSysProcStatusKb(String key);
+
     /** @return sync availability (0: none; 1: client; 2: server) */
     static native int nativeGetSupportedSync();
 
@@ -405,7 +409,6 @@ public static boolean isDatabaseOpen(Object context, @Nullable String dbNameOrNu
      */
     public static boolean isDatabaseOpen(@Nullable File baseDirectoryOrNull,
                                          @Nullable String dbNameOrNull) throws IOException {
-        
         File dbDir = BoxStoreBuilder.getDbDir(baseDirectoryOrNull, dbNameOrNull);
         return isFileOpen(dbDir.getCanonicalPath());
     }
@@ -420,6 +423,43 @@ public static boolean isDatabaseOpen(File directory) throws IOException {
         return isFileOpen(directory.getCanonicalPath());
     }
 
+    /**
+     * Linux only: extracts a kB value from /proc/meminfo (system wide memory information).
+     * A couple of interesting keys (from 'man proc'):
+     * - MemTotal: Total usable RAM (i.e., physical RAM minus a few reserved bits and the kernel binary code).
+     * - MemFree:  The sum of LowFree+HighFree.
+     * - MemAvailable: An estimate of how much memory is available for starting new applications, without swapping.
+     *
+     * @param key The string identifying the wanted line from /proc/meminfo to extract a Kb value from. E.g. "MemTotal".
+     * @return Kb value or 0 on failure
+     */
+    @Experimental
+    static long sysProcMeminfoKb(String key) {
+        return nativeSysProcMeminfoKb(key);
+    }
+
+    /**
+     * Linux only: extracts a kB value from /proc/self/status (process specific information).
+     * A couple of interesting keys (from 'man proc'):
+     * - VmPeak: Peak virtual memory size.
+     * - VmSize: Virtual memory size.
+     * - VmHWM: Peak resident set size ("high water mark").
+     * - VmRSS: Resident set size.  Note that the value here is the sum of RssAnon, RssFile, and RssShmem.
+     * - RssAnon: Size of resident anonymous memory.  (since Linux 4.5).
+     * - RssFile: Size of resident file mappings.  (since Linux 4.5).
+     * - RssShmem: Size of resident shared memory (includes System V shared  memory,  mappings  from  tmpfs(5),
+     * and shared anonymous mappings).  (since Linux 4.5).
+     * - VmData, VmStk, VmExe: Size of data, stack, and text segments.
+     * - VmLib: Shared library code size.
+     *
+     * @param key The string identifying the wanted line from /proc/self/status to extract a Kb value from. E.g. "VmSize".
+     * @return Kb value or 0 on failure
+     */
+    @Experimental
+    static long sysProcStatusKb(String key) {
+        return nativeSysProcStatusKb(key);
+    }
+
     /**
      * The size in bytes occupied by the data file on disk.
      *

tests/objectbox-java-test/src/test/java/io/objectbox/BoxStoreTest.java

@@ -19,6 +19,7 @@
 import org.junit.Test;
 
 import java.io.File;
+import java.util.Locale;
 import java.util.concurrent.Callable;
 
 import javax.annotation.Nullable;
@@ -240,4 +241,21 @@ public void testIsObjectBrowserAvailable() {
         assertFalse(BoxStore.isObjectBrowserAvailable());
     }
 
+    @Test
+    public void testSysProc() {
+        long vmRss = BoxStore.sysProcStatusKb("VmRSS");
+        long memAvailable = BoxStore.sysProcMeminfoKb("MemAvailable");
+
+        final String osName = System.getProperty("os.name");
+        if (osName.toLowerCase().contains("linux")) {
+            System.out.println("VmRSS: " + vmRss);
+            System.out.println("MemAvailable: " + memAvailable);
+            assertTrue(vmRss > 0);
+            assertTrue(memAvailable > 0);
+        } else {
+            assertEquals(vmRss, 0);
+            assertEquals(memAvailable, 0);
+        }
+    }
+
 }