SliTaz Packages

e4rat reduces disk access times through physical file reallocation. It is based on the online defragmentation ioctl EXT4IOCMOVE_EXT from the ext4 filesystem, which was introduced in Linux Kernel 2.6.31. Therefore, other filesystem types or earlier versions of extended filesystems are not supported.

e4rat consists of three binaries. The first is e4rat-collect. Its purpose is to gather relevant files by monitoring file accesses during an application startup. The generated file list is the fundament of the second step. With the second step, e4rat-realloc, files are placed physically in a row on disk. The reallocation of the files' content yields a higher disk transfer rate which accelerates program start processes.

Third, you can also read-ahead files to gain a higher cache hit rate. e4rat-preload transfers files into memory in parallel to program startup.

Because a file consists of file content and its I-Node information the preloading process is divided into two steps. First, it reads the I-Nodes' information which are still spread over the entire filesystem. In the second step, the files' content is read without causing any disk seeks.

For more information see: e4rat-collect(8), e4rat-realloc(8), e4rat-preload(8) and e4rat.conf(5).

SAMPLE USAGE: Accelerate the boot process

Run e4rat-collect as init process through adding following line to Kernel parameters:

init=/sbin/e4rat-collect

After e4rat-collect has terminated the generated file list is stored at:

/var/lib/e4rat/startup.log

Before reallocating boot files it is recommaned to switch to runlevel 1 to stop most of all running proceses to gain write access to the process binary file:

init 1

Reallocating boot files:

e4rat-realloc  /var/lib/e4rat/startup.log

To start e4rat-preload as initial process append following to kernel your parameters:

init=/sbin/e4rat-preload