- The program can use
pre-fetching to
reduce processing time.
- Pre-fetching:
(a.k.a. double buffer)
- The program allocates
two or more buffers to
process data from a file:
- Data is read in
a buffer:
- When buffer is full,
program processes the data.
And at the same time, more data is read in the other buffer:
- Rotate buffers when
done processing data
in buffer:
- The program allocates
two or more buffers to
process data from a file:
- Operating System:
- Operating System = a program that manages the resources in a computer
- Buffering technique used in
(modern) operating systems:
- The operating system uses
buffering when
a file is
accessed:
Buffers located inside the operating system are used to pre-fetch data blocks from an opened file
The buffers in the operating system are organized as a circular buffer (Wikipedia: click here)
- The operating system uses
buffering when
a file is
accessed:
- Buffering operation:
- User program does
not need to
use pre-fetching and uses
1 buffer to read a file:
- When the user program
opens a file, the
operating system will
allocate N buffers and
fill them:
- When the user program
reads from the file, the
operating system will
transfer a buffer to
the user buffer:
- The user program
can process the
data block in its
buffer
At the same time, The operating system will read the next block into the emptied buffer:
- User program does
not need to
use pre-fetching and uses
1 buffer to read a file: