commit e4e5381e0fe89074ebc807e33635b96acc2ec2df
author Chenbo Feng <fengc@google.com> Thu Jan 10 14:48:54 2019 -0800
committer Chenbo Feng <fengc@google.com> Tue Jan 22 13:50:35 2019 -0800
tree 7a54ee98bf386b5f85bb87794d6a054e56cd1ed7
parent 95a5f485f9b1df47574b59b71c21120c057b61c6

Use delta reads for per uid traffic stats

For the detailed network stats of each uid and tag, the native
implementation provides delta read instead of consistent stats
data since boot. Every time the readNetworkStatsDetail function gets
called, the data pulled will be cleared. We will keep a persistent data
since boot in NetworkStatsService instead.

Fixed some checkstyle complains in related files as well.

Bug: 79171384
Test: android.app.usage.cts.NetworkUsageStatsTest
      NetworkStatsServiceTest
Change-Id: I50bcf278739135081d522e50b0e88d76fd9ab131

core/java/com/android/internal/net/NetworkStatsFactory.java

diff --git a/core/java/com/android/internal/net/NetworkStatsFactory.java b/core/java/com/android/internal/net/NetworkStatsFactory.java
index 9bacf9b..f848346 100644
--- a/core/java/com/android/internal/net/NetworkStatsFactory.java
+++ b/core/java/com/android/internal/net/NetworkStatsFactory.java
@@ -64,6 +64,9 @@
 
     private boolean mUseBpfStats;
 
+    // A persistent Snapshot since device start for eBPF stats
+    private final NetworkStats mPersistSnapshot;
+
     // TODO: only do adjustments in NetworkStatsService and remove this.
     /**
      * (Stacked interface) -> (base interface) association for all connected ifaces since boot.
@@ -135,6 +138,7 @@
         mStatsXtIfaceFmt = new File(procRoot, "net/xt_qtaguid/iface_stat_fmt");
         mStatsXtUid = new File(procRoot, "net/xt_qtaguid/stats");
         mUseBpfStats = useBpfStats;
+        mPersistSnapshot = new NetworkStats(SystemClock.elapsedRealtime(), -1);
     }
 
     public NetworkStats readBpfNetworkStatsDev() throws IOException {
@@ -268,6 +272,7 @@
         return stats;
     }
 
+    // TODO: delete the lastStats parameter
     private NetworkStats readNetworkStatsDetailInternal(int limitUid, String[] limitIfaces,
             int limitTag, NetworkStats lastStats) throws IOException {
         if (USE_NATIVE_PARSING) {
@@ -278,16 +283,28 @@
             } else {
                 stats = new NetworkStats(SystemClock.elapsedRealtime(), -1);
             }
-            if (nativeReadNetworkStatsDetail(stats, mStatsXtUid.getAbsolutePath(), limitUid,
-                    limitIfaces, limitTag, mUseBpfStats) != 0) {
-                throw new IOException("Failed to parse network stats");
+            if (mUseBpfStats) {
+                if (nativeReadNetworkStatsDetail(stats, mStatsXtUid.getAbsolutePath(), UID_ALL,
+                        null, TAG_ALL, mUseBpfStats) != 0) {
+                    throw new IOException("Failed to parse network stats");
+                }
+                mPersistSnapshot.setElapsedRealtime(stats.getElapsedRealtime());
+                mPersistSnapshot.combineAllValues(stats);
+                NetworkStats result = mPersistSnapshot.clone();
+                result.filter(limitUid, limitIfaces, limitTag);
+                return result;
+            } else {
+                if (nativeReadNetworkStatsDetail(stats, mStatsXtUid.getAbsolutePath(), limitUid,
+                        limitIfaces, limitTag, mUseBpfStats) != 0) {
+                    throw new IOException("Failed to parse network stats");
+                }
+                if (SANITY_CHECK_NATIVE) {
+                    final NetworkStats javaStats = javaReadNetworkStatsDetail(mStatsXtUid, limitUid,
+                            limitIfaces, limitTag);
+                    assertEquals(javaStats, stats);
+                }
+                return stats;
             }
-            if (SANITY_CHECK_NATIVE) {
-                final NetworkStats javaStats = javaReadNetworkStatsDetail(mStatsXtUid, limitUid,
-                        limitIfaces, limitTag);
-                assertEquals(javaStats, stats);
-            }
-            return stats;
         } else {
             return javaReadNetworkStatsDetail(mStatsXtUid, limitUid, limitIfaces, limitTag);
         }