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| author | Hans-G?nter Theisgen |
|---|---|
| date | Fri Jan 24 16:35:42 2020 +0100 (2020-01-24) |
| parents | |
| children |
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1 e4rat reduces disk access times through physical file reallocation. It is based
2 on the online defragmentation ioctl EXT4_IOC_MOVE_EXT from the ext4 filesystem,
3 which was introduced in Linux Kernel 2.6.31. Therefore, other filesystem types
4 or earlier versions of extended filesystems are not supported.
6 e4rat consists of three binaries. The first is e4rat-collect. Its purpose is to
7 gather relevant files by monitoring file accesses during an application startup.
8 The generated file list is the fundament of the second step. With the second
9 step, e4rat-realloc, files are placed physically in a row on disk.
10 The reallocation of the files' content yields a higher disk transfer rate which
11 accelerates program start processes.
13 Third, you can also read-ahead files to gain a higher cache hit rate.
14 e4rat-preload transfers files into memory in parallel to program startup.
16 Because a file consists of file content and its I-Node information the
17 preloading process is divided into two steps. First, it reads the I-Nodes'
18 information which are still spread over the entire filesystem. In the second
19 step, the files' content is read without causing any disk seeks.
21 For more information see: e4rat-collect(8), e4rat-realloc(8), e4rat-preload(8)
22 and e4rat.conf(5).
25 SAMPLE USAGE: Accelerate the boot process
26 -------------
28 Run e4rat-collect as init process through adding following line to Kernel
29 parameters:
31 init=/sbin/e4rat-collect
33 After e4rat-collect has terminated the generated file list is stored at:
35 /var/lib/e4rat/startup.log
37 Before reallocating boot files it is recommaned to switch to runlevel 1 to stop
38 most of all running proceses to gain write access to the process binary file:
40 init 1
42 Reallocating boot files:
44 e4rat-realloc /var/lib/e4rat/startup.log
46 To start e4rat-preload as initial process append following to kernel your
47 parameters:
49 init=/sbin/e4rat-preload