91 lines
3.6 KiB
Java
91 lines
3.6 KiB
Java
/*
|
|
* Copyright (C) 2017 The Android Open Source Project
|
|
*
|
|
* Licensed under the Apache License, Version 2.0 (the "License");
|
|
* you may not use this file except in compliance with the License.
|
|
* You may obtain a copy of the License at
|
|
*
|
|
* http://www.apache.org/licenses/LICENSE-2.0
|
|
*
|
|
* Unless required by applicable law or agreed to in writing, software
|
|
* distributed under the License is distributed on an "AS IS" BASIS,
|
|
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
* See the License for the specific language governing permissions and
|
|
* limitations under the License.
|
|
*/
|
|
|
|
package com.android.internal.os;
|
|
|
|
import android.util.Slog;
|
|
|
|
import com.android.internal.annotations.VisibleForTesting;
|
|
|
|
import java.util.Arrays;
|
|
|
|
/**
|
|
* Generates the bucket thresholds (with a custom logarithmic scale) for a histogram to store
|
|
* latency samples in.
|
|
*/
|
|
@android.ravenwood.annotation.RavenwoodKeepWholeClass
|
|
public class BinderLatencyBuckets {
|
|
private static final String TAG = "BinderLatencyBuckets";
|
|
private final int[] mBuckets;
|
|
|
|
/**
|
|
* @param bucketCount the number of buckets the histogram should have
|
|
* @param firstBucketSize the size of the first bucket (used to avoid excessive small buckets)
|
|
* @param scaleFactor the rate in which each consecutive bucket increases (before rounding)
|
|
*/
|
|
public BinderLatencyBuckets(int bucketCount, int firstBucketSize, float scaleFactor) {
|
|
int[] buffer = new int[bucketCount - 1];
|
|
buffer[0] = firstBucketSize;
|
|
|
|
// Last value and the target are disjoint as we never want to create buckets smaller than 1.
|
|
double lastTarget = firstBucketSize;
|
|
|
|
// First bucket is already created and the last bucket is anything greater than the final
|
|
// bucket in the list, so create 'bucketCount' - 2 buckets.
|
|
for (int i = 1; i < bucketCount - 1; i++) {
|
|
// Increase the target bucket limit value by the scale factor.
|
|
double nextTarget = lastTarget * scaleFactor;
|
|
|
|
if (nextTarget > Integer.MAX_VALUE) {
|
|
// Do not throw an exception here as this should not affect binder calls.
|
|
Slog.w(TAG, "Attempted to create a bucket larger than maxint");
|
|
mBuckets = Arrays.copyOfRange(buffer, 0, i);
|
|
return;
|
|
}
|
|
|
|
if ((int) nextTarget > buffer[i - 1]) {
|
|
// Convert the target bucket limit value to an integer.
|
|
buffer[i] = (int) nextTarget;
|
|
} else {
|
|
// Avoid creating redundant buckets, so bucket size should be 1 at a minimum.
|
|
buffer[i] = buffer[i - 1] + 1;
|
|
}
|
|
lastTarget = nextTarget;
|
|
}
|
|
mBuckets = buffer;
|
|
}
|
|
|
|
/** Gets the bucket index to insert the provided sample in. */
|
|
public int sampleToBucket(int sample) {
|
|
if (sample >= mBuckets[mBuckets.length - 1]) {
|
|
return mBuckets.length;
|
|
}
|
|
|
|
// Binary search returns the element index if it is contained in the list - in this case the
|
|
// correct bucket is the index after as we use [minValue, maxValue) for bucket boundaries.
|
|
// Otherwise, it returns (-(insertion point) - 1), where insertion point is the point where
|
|
// to insert the element so that the array remains sorted - in this case the bucket index
|
|
// is the insertion point.
|
|
int searchResult = Arrays.binarySearch(mBuckets, sample);
|
|
return searchResult < 0 ? -(1 + searchResult) : searchResult + 1;
|
|
}
|
|
|
|
@VisibleForTesting
|
|
public int[] getBuckets() {
|
|
return mBuckets;
|
|
}
|
|
}
|