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/*
* Copyright (c) 2024, Google LLC and others
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Distribution License v. 1.0 which is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
package org.eclipse.jgit.internal.storage.dfs;
import static org.eclipse.jgit.internal.storage.dfs.DfsBlockCacheTable.BlockCacheStats;
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.atomic.AtomicReference;
import org.eclipse.jgit.internal.storage.pack.PackExt;
/**
* Keeps track of stats for a Block Cache table.
*/
class DfsBlockCacheStats implements BlockCacheStats {
private final String name;
/**
* Number of times a block was found in the cache, per pack file extension.
*/
private final AtomicReference<AtomicLong[]> statHit;
/**
* Number of times a block was not found, and had to be loaded, per pack
* file extension.
*/
private final AtomicReference<AtomicLong[]> statMiss;
/**
* Number of blocks evicted due to cache being full, per pack file
* extension.
*/
private final AtomicReference<AtomicLong[]> statEvict;
/**
* Number of bytes currently loaded in the cache, per pack file extension.
*/
private final AtomicReference<AtomicLong[]> liveBytes;
DfsBlockCacheStats() {
this(""); //$NON-NLS-1$
}
DfsBlockCacheStats(String name) {
this.name = name;
statHit = new AtomicReference<>(newCounters());
statMiss = new AtomicReference<>(newCounters());
statEvict = new AtomicReference<>(newCounters());
liveBytes = new AtomicReference<>(newCounters());
}
@Override
public String getName() {
return name;
}
/**
* Increment the {@code statHit} count.
*
* @param key
* key identifying which liveBytes entry to update.
*/
void incrementHit(DfsStreamKey key) {
getStat(statHit, key).incrementAndGet();
}
/**
* Increment the {@code statMiss} count.
*
* @param key
* key identifying which liveBytes entry to update.
*/
void incrementMiss(DfsStreamKey key) {
getStat(statMiss, key).incrementAndGet();
}
/**
* Increment the {@code statEvict} count.
*
* @param key
* key identifying which liveBytes entry to update.
*/
void incrementEvict(DfsStreamKey key) {
getStat(statEvict, key).incrementAndGet();
}
/**
* Add {@code size} to the {@code liveBytes} count.
*
* @param key
* key identifying which liveBytes entry to update.
* @param size
* amount to increment the count by.
*/
void addToLiveBytes(DfsStreamKey key, long size) {
getStat(liveBytes, key).addAndGet(size);
}
@Override
public long[] getCurrentSize() {
return getStatVals(liveBytes);
}
@Override
public long[] getHitCount() {
return getStatVals(statHit);
}
@Override
public long[] getMissCount() {
return getStatVals(statMiss);
}
@Override
public long[] getTotalRequestCount() {
AtomicLong[] hit = statHit.get();
AtomicLong[] miss = statMiss.get();
long[] cnt = new long[Math.max(hit.length, miss.length)];
for (int i = 0; i < hit.length; i++) {
cnt[i] += hit[i].get();
}
for (int i = 0; i < miss.length; i++) {
cnt[i] += miss[i].get();
}
return cnt;
}
@Override
public long[] getHitRatio() {
AtomicLong[] hit = statHit.get();
AtomicLong[] miss = statMiss.get();
long[] ratio = new long[Math.max(hit.length, miss.length)];
for (int i = 0; i < ratio.length; i++) {
if (i >= hit.length) {
ratio[i] = 0;
} else if (i >= miss.length) {
ratio[i] = 100;
} else {
long hitVal = hit[i].get();
long missVal = miss[i].get();
long total = hitVal + missVal;
ratio[i] = total == 0 ? 0 : hitVal * 100 / total;
}
}
return ratio;
}
@Override
public long[] getEvictions() {
return getStatVals(statEvict);
}
private static AtomicLong[] newCounters() {
AtomicLong[] ret = new AtomicLong[PackExt.values().length];
for (int i = 0; i < ret.length; i++) {
ret[i] = new AtomicLong();
}
return ret;
}
private static long[] getStatVals(AtomicReference<AtomicLong[]> stat) {
AtomicLong[] stats = stat.get();
long[] cnt = new long[stats.length];
for (int i = 0; i < stats.length; i++) {
cnt[i] = stats[i].get();
}
return cnt;
}
private static AtomicLong getStat(AtomicReference<AtomicLong[]> stats,
DfsStreamKey key) {
int pos = key.packExtPos;
while (true) {
AtomicLong[] vals = stats.get();
if (pos < vals.length) {
return vals[pos];
}
AtomicLong[] expect = vals;
vals = new AtomicLong[Math.max(pos + 1, PackExt.values().length)];
System.arraycopy(expect, 0, vals, 0, expect.length);
for (int i = expect.length; i < vals.length; i++) {
vals[i] = new AtomicLong();
}
if (stats.compareAndSet(expect, vals)) {
return vals[pos];
}
}
}
}
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