8KB와 1MB 사이의 버퍼 크기를 가진 두 개의 동일한 3,8gb 파일을 비교하는 세 가지 방법을 시도했습니다. 첫 번째 첫 번째 방법은 두 개의 버퍼링 된 입력 스트림을 사용했습니다.
두 번째 방법은 두 개의 다른 스레드를 읽고 세 번째 방법으로 비교하는 스레드 풀을 사용합니다. 이것은 높은 CPU 사용량을 희생하여 약간 높은 처리량을 얻었습니다. 스레드 풀 관리는 짧은 실행 작업으로 많은 오버 헤드를 필요로합니다.
세 번째 방법은 당신이 볼 수 있듯이, 일반적인 접근 방식은 크게 다르지 않다 laginimaineb
에 의해 게시 된, NIO 사용합니다. 올바른 버퍼 크기가 더 중요합니다.
스레드를 사용하여 1 바이트 이하를 읽는 것이 이상합니다. 힘든 오류를 발견하지 못했습니다. 사용
comparing just with two streams
I was equal, even after 3684070360 bytes and reading for 704813 ms (4,98MB/sec * 2) with a buffer size of 8 kB
I was equal, even after 3684070360 bytes and reading for 578563 ms (6,07MB/sec * 2) with a buffer size of 16 kB
I was equal, even after 3684070360 bytes and reading for 515422 ms (6,82MB/sec * 2) with a buffer size of 32 kB
I was equal, even after 3684070360 bytes and reading for 534532 ms (6,57MB/sec * 2) with a buffer size of 64 kB
I was equal, even after 3684070360 bytes and reading for 422953 ms (8,31MB/sec * 2) with a buffer size of 128 kB
I was equal, even after 3684070360 bytes and reading for 793359 ms (4,43MB/sec * 2) with a buffer size of 256 kB
I was equal, even after 3684070360 bytes and reading for 746344 ms (4,71MB/sec * 2) with a buffer size of 512 kB
I was equal, even after 3684070360 bytes and reading for 669969 ms (5,24MB/sec * 2) with a buffer size of 1024 kB
comparing with threads
I was equal, even after 3684070359 bytes and reading for 602391 ms (5,83MB/sec * 2) with a buffer size of 8 kB
I was equal, even after 3684070359 bytes and reading for 523156 ms (6,72MB/sec * 2) with a buffer size of 16 kB
I was equal, even after 3684070359 bytes and reading for 527547 ms (6,66MB/sec * 2) with a buffer size of 32 kB
I was equal, even after 3684070359 bytes and reading for 276750 ms (12,69MB/sec * 2) with a buffer size of 64 kB
I was equal, even after 3684070359 bytes and reading for 493172 ms (7,12MB/sec * 2) with a buffer size of 128 kB
I was equal, even after 3684070359 bytes and reading for 696781 ms (5,04MB/sec * 2) with a buffer size of 256 kB
I was equal, even after 3684070359 bytes and reading for 727953 ms (4,83MB/sec * 2) with a buffer size of 512 kB
I was equal, even after 3684070359 bytes and reading for 741000 ms (4,74MB/sec * 2) with a buffer size of 1024 kB
comparing with nio
I was equal, even after 3684070360 bytes and reading for 661313 ms (5,31MB/sec * 2) with a buffer size of 8 kB
I was equal, even after 3684070360 bytes and reading for 656156 ms (5,35MB/sec * 2) with a buffer size of 16 kB
I was equal, even after 3684070360 bytes and reading for 491781 ms (7,14MB/sec * 2) with a buffer size of 32 kB
I was equal, even after 3684070360 bytes and reading for 317360 ms (11,07MB/sec * 2) with a buffer size of 64 kB
I was equal, even after 3684070360 bytes and reading for 643078 ms (5,46MB/sec * 2) with a buffer size of 128 kB
I was equal, even after 3684070360 bytes and reading for 865016 ms (4,06MB/sec * 2) with a buffer size of 256 kB
I was equal, even after 3684070360 bytes and reading for 716796 ms (4,90MB/sec * 2) with a buffer size of 512 kB
I was equal, even after 3684070360 bytes and reading for 652016 ms (5,39MB/sec * 2) with a buffer size of 1024 kB
코드 :
import junit.framework.Assert;
import org.junit.Before;
import org.junit.Test;
import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.text.DecimalFormat;
import java.text.NumberFormat;
import java.util.Arrays;
import java.util.concurrent.*;
public class FileCompare {
private static final int MIN_BUFFER_SIZE = 1024 * 8;
private static final int MAX_BUFFER_SIZE = 1024 * 1024;
private String fileName1;
private String fileName2;
private long start;
private long totalbytes;
@Before
public void createInputStream() {
fileName1 = "bigFile.1";
fileName2 = "bigFile.2";
}
@Test
public void compareTwoFiles() throws IOException {
System.out.println("comparing just with two streams");
int currentBufferSize = MIN_BUFFER_SIZE;
while (currentBufferSize <= MAX_BUFFER_SIZE) {
compareWithBufferSize(currentBufferSize);
currentBufferSize *= 2;
}
}
@Test
public void compareTwoFilesFutures()
throws IOException, ExecutionException, InterruptedException {
System.out.println("comparing with threads");
int myBufferSize = MIN_BUFFER_SIZE;
while (myBufferSize <= MAX_BUFFER_SIZE) {
start = System.currentTimeMillis();
totalbytes = 0;
compareWithBufferSizeFutures(myBufferSize);
myBufferSize *= 2;
}
}
@Test
public void compareTwoFilesNio() throws IOException {
System.out.println("comparing with nio");
int myBufferSize = MIN_BUFFER_SIZE;
while (myBufferSize <= MAX_BUFFER_SIZE) {
start = System.currentTimeMillis();
totalbytes = 0;
boolean wasEqual = isEqualsNio(myBufferSize);
if (wasEqual) {
printAfterEquals(myBufferSize);
} else {
Assert.fail("files were not equal");
}
myBufferSize *= 2;
}
}
private void compareWithBufferSize(int myBufferSize) throws IOException {
final BufferedInputStream inputStream1 =
new BufferedInputStream(
new FileInputStream(new File(fileName1)),
myBufferSize);
byte[] buff1 = new byte[myBufferSize];
final BufferedInputStream inputStream2 =
new BufferedInputStream(
new FileInputStream(new File(fileName2)),
myBufferSize);
byte[] buff2 = new byte[myBufferSize];
int read1;
start = System.currentTimeMillis();
totalbytes = 0;
while ((read1 = inputStream1.read(buff1)) != -1) {
totalbytes += read1;
int read2 = inputStream2.read(buff2);
if (read1 != read2) {
break;
}
if (!Arrays.equals(buff1, buff2)) {
break;
}
}
if (read1 == -1) {
printAfterEquals(myBufferSize);
} else {
Assert.fail("files were not equal");
}
inputStream1.close();
inputStream2.close();
}
private void compareWithBufferSizeFutures(int myBufferSize)
throws ExecutionException, InterruptedException, IOException {
final BufferedInputStream inputStream1 =
new BufferedInputStream(
new FileInputStream(
new File(fileName1)),
myBufferSize);
final BufferedInputStream inputStream2 =
new BufferedInputStream(
new FileInputStream(
new File(fileName2)),
myBufferSize);
final boolean wasEqual = isEqualsParallel(myBufferSize, inputStream1, inputStream2);
if (wasEqual) {
printAfterEquals(myBufferSize);
} else {
Assert.fail("files were not equal");
}
inputStream1.close();
inputStream2.close();
}
private boolean isEqualsParallel(int myBufferSize
, final BufferedInputStream inputStream1
, final BufferedInputStream inputStream2)
throws InterruptedException, ExecutionException {
final byte[] buff1Even = new byte[myBufferSize];
final byte[] buff1Odd = new byte[myBufferSize];
final byte[] buff2Even = new byte[myBufferSize];
final byte[] buff2Odd = new byte[myBufferSize];
final Callable<Integer> read1Even = new Callable<Integer>() {
public Integer call() throws Exception {
return inputStream1.read(buff1Even);
}
};
final Callable<Integer> read2Even = new Callable<Integer>() {
public Integer call() throws Exception {
return inputStream2.read(buff2Even);
}
};
final Callable<Integer> read1Odd = new Callable<Integer>() {
public Integer call() throws Exception {
return inputStream1.read(buff1Odd);
}
};
final Callable<Integer> read2Odd = new Callable<Integer>() {
public Integer call() throws Exception {
return inputStream2.read(buff2Odd);
}
};
final Callable<Boolean> oddEqualsArray = new Callable<Boolean>() {
public Boolean call() throws Exception {
return Arrays.equals(buff1Odd, buff2Odd);
}
};
final Callable<Boolean> evenEqualsArray = new Callable<Boolean>() {
public Boolean call() throws Exception {
return Arrays.equals(buff1Even, buff2Even);
}
};
ExecutorService executor = Executors.newCachedThreadPool();
boolean isEven = true;
Future<Integer> read1 = null;
Future<Integer> read2 = null;
Future<Boolean> isEqual = null;
int lastSize = 0;
while (true) {
if (isEqual != null) {
if (!isEqual.get()) {
return false;
} else if (lastSize == -1) {
return true;
}
}
if (read1 != null) {
lastSize = read1.get();
totalbytes += lastSize;
final int size2 = read2.get();
if (lastSize != size2) {
return false;
}
}
isEven = !isEven;
if (isEven) {
if (read1 != null) {
isEqual = executor.submit(oddEqualsArray);
}
read1 = executor.submit(read1Even);
read2 = executor.submit(read2Even);
} else {
if (read1 != null) {
isEqual = executor.submit(evenEqualsArray);
}
read1 = executor.submit(read1Odd);
read2 = executor.submit(read2Odd);
}
}
}
private boolean isEqualsNio(int myBufferSize) throws IOException {
FileChannel first = null, seconde = null;
try {
first = new FileInputStream(fileName1).getChannel();
seconde = new FileInputStream(fileName2).getChannel();
if (first.size() != seconde.size()) {
return false;
}
ByteBuffer firstBuffer = ByteBuffer.allocateDirect(myBufferSize);
ByteBuffer secondBuffer = ByteBuffer.allocateDirect(myBufferSize);
int firstRead, secondRead;
while (first.position() < first.size()) {
firstRead = first.read(firstBuffer);
totalbytes += firstRead;
secondRead = seconde.read(secondBuffer);
if (firstRead != secondRead) {
return false;
}
if (!nioBuffersEqual(firstBuffer, secondBuffer, firstRead)) {
return false;
}
}
return true;
} finally {
if (first != null) {
first.close();
}
if (seconde != null) {
seconde.close();
}
}
}
private static boolean nioBuffersEqual(ByteBuffer first, ByteBuffer second, final int length) {
if (first.limit() != second.limit() || length > first.limit()) {
return false;
}
first.rewind();
second.rewind();
for (int i = 0; i < length; i++) {
if (first.get() != second.get()) {
return false;
}
}
return true;
}
private void printAfterEquals(int myBufferSize) {
NumberFormat nf = new DecimalFormat("#.00");
final long dur = System.currentTimeMillis() - start;
double seconds = dur/1000d;
double megabytes = totalbytes/1024/1024;
double rate = (megabytes)/seconds;
System.out.println("I was equal, even after " + totalbytes
+ " bytes and reading for " + dur
+ " ms (" + nf.format(rate) + "MB/sec * 2)" +
" with a buffer size of " + myBufferSize/1024 + " kB");
}
}
참고 : 기본적으로 DMA/SATA 기술은 모든 파일 I/O 작업 (현재 OS에서는 잘)을 위해 OS에서 처리합니다. –