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Commit e1b6c742 authored by Ivo Kay's avatar Ivo Kay Committed by Android (Google) Code Review
Browse files

Merge "Account for interpolation loss in cumulative network stats" into main

parents 7799ecf1 68c8ddab

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);

        }

    }