bad I/O performance in BufferedInputStream

[Jimmy Zhang]

hi,
I am trying to read 4 files into memory, I am getting horrible performance.
Anyone has suggestions on how to imporve the performance. notice that I
have already used BufferedInputStream wherever I can.

Am I better off open and read from one file or from many different files??

Thanks,
Jimmy


File f = new File(vtd);
int size = ((int) f.length()) ;

vtdTokenBuffer = new LongBuffer();
DataInputStream bi = new DataInputStream(new BufferedInputStream(new
FileInputStream(vtd)));
size = size>>3;

for(int i = 0;i<(size);i++)
{
long l = bi.readLong();
}

bi.close();

f = new File(l1);
size = (int) f.length();

bi = new DataInputStream(new BufferedInputStream(new
FileInputStream(l1)));
size = size>>3;
for(int i = 0;i<(size);i++)
{
long l = bi.readLong();
//System.out.println(" Level 1 "+Long.toHexString(l));
//cacheLevelOne.append(l);
}
bi.close();

f = new File(l2);
size = (int) f.length();

bi = new DataInputStream(new BufferedInputStream(new
FileInputStream(l2)));
size = size >>3;
for(int i = 0;i<(size);i++)
{
bi.readLong();
}
bi.close();

f = new File(l3);
size = (int) f.length();
cacheLevelThree = new IntBuffer();
bi = new DataInputStream(new BufferedInputStream(new
FileInputStream(l3)));
size = size>>2;
for(int i = 0;i<(size);i++)
{
int l = bi.readInt();
}
bi.close();

 

[Roedy Green]

bi = new DataInputStream(new BufferedInputStream(new
FileInputStream(l1)));

try specifying a honking big buffersize on your BufferedInputStream.

See http://mindprod.com/jgloss/buffer.html

Other approaches:

read the entire file in one giant io with UNBufferedInputStream into
an array of bytes. see http://mindprod.com/products.html#HUNKIO


Look into nio classes.