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Commit 68c8ddab authored by Ivo Kay's avatar Ivo Kay
Browse files

Account for interpolation loss in cumulative network stats 

Bug: 352537247
Test: atest FrameworksServicesTests:NetworkStatsAccumulatorTest
Flag: com.android.server.stats.accumulate_network_stats_since_boot
Change-Id: I95a04c3b32bc8379f3cb9453f29df67ae87eefae
parent 367acd63

services/core/java/com/android/server/stats/pull/netstats/NetworkStatsAccumulator.java

+20 −4
Original line number Diff line number Diff line
@@ -19,6 +19,7 @@ package com.android.server.stats.pull.netstats; 
import android.annotation.NonNull;

import android.net.NetworkStats;

import android.net.NetworkTemplate;

import android.util.Log;



import java.util.Objects;
@@ -33,6 +34,7 @@ import java.util.Objects; 
 */

public class NetworkStatsAccumulator {



    private static final String TAG = "NetworkStatsAccumulator";

    private final NetworkTemplate mTemplate;

    private final boolean mWithTags;

    private final long mBucketDurationMillis;
@@ -57,8 +59,9 @@ public class NetworkStatsAccumulator { 
    @NonNull

    public NetworkStats queryStats(long currentTimeMillis,

            @NonNull StatsQueryFunction queryFunction) {

        maybeExpandSnapshot(currentTimeMillis, queryFunction);

        return snapshotPlusFollowingStats(currentTimeMillis, queryFunction);

        NetworkStats completeStats = snapshotPlusFollowingStats(currentTimeMillis, queryFunction);

        maybeExpandSnapshot(currentTimeMillis, completeStats, queryFunction);

        return completeStats;

    }



    /**
@@ -72,15 +75,28 @@ public class NetworkStatsAccumulator { 
     * Expands the internal cumulative stats snapshot, if possible, by querying NetworkStats.

     */

    private void maybeExpandSnapshot(long currentTimeMillis,

            NetworkStats completeStatsUntilCurrentTime,

            @NonNull StatsQueryFunction queryFunction) {

        // Update snapshot only if it is possible to expand it by at least one full bucket, and only

        // if the new snapshot's end is not in the active bucket.

        long newEndTimeMillis = currentTimeMillis - mBucketDurationMillis;

        if (newEndTimeMillis - mSnapshotEndTimeMillis > mBucketDurationMillis) {

            NetworkStats extraStats = queryFunction.queryNetworkStats(mTemplate, mWithTags,

                    mSnapshotEndTimeMillis, newEndTimeMillis);

            Log.v(TAG,

                    "Expanding snapshot (mTemplate=" + mTemplate + ", mWithTags=" + mWithTags

                            + ") from " + mSnapshotEndTimeMillis + " to " + newEndTimeMillis

                            + " at " + currentTimeMillis);

            NetworkStats extraStats = queryFunction.queryNetworkStats(

                    mTemplate, mWithTags, mSnapshotEndTimeMillis, newEndTimeMillis);

            mSnapshot = mSnapshot.add(extraStats);

            mSnapshotEndTimeMillis = newEndTimeMillis;



            // NetworkStats queries interpolate historical data using integers maths, which makes

            // queries non-transitive: Query(t0, t1) + Query(t1, t2) <= Query(t0, t2).

            // Compute interpolation data loss from moving the snapshot's end-point, and add it to

            // the snapshot to avoid under-counting.

            NetworkStats newStats = snapshotPlusFollowingStats(currentTimeMillis, queryFunction);

            NetworkStats interpolationLoss = completeStatsUntilCurrentTime.subtract(newStats);

            mSnapshot = mSnapshot.add(interpolationLoss);

        }

    }