Difference between revisions of "E4rat"

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(Alternative: e4rat-preload-lite: Link to kernel parameters.)
(Alternative: e4rat-preload-lite: changed Note into Note box)
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Now for the nitty-gritty:
 
Now for the nitty-gritty:
 
===e4rat-collect===
 
===e4rat-collect===
To have e4rat collect a list of files you will need to append the following to your linux (or 'kernel') line in your '''/boot/grub/menu.lst''' (grub legacy) or '''/boot/grub/grub.cfg''' (grub2) file. For example:
+
To have e4rat collect a list of files you will need to append {{ic|1=init=/sbin/e4rat-collect}} to your [[kernel parameters]].For example:
  
 
{{bc|1=kernel /vmlinuz0linux root=/dev/disk/by-label/ARCH init=/sbin/e4rat-collect ro 5}}
 
{{bc|1=kernel /vmlinuz0linux root=/dev/disk/by-label/ARCH init=/sbin/e4rat-collect ro 5}}
Line 52: Line 52:
 
Upon successful boot and after having waited the allotted time you should see the following file: '''/var/lib/e4rat/startup.log'''
 
Upon successful boot and after having waited the allotted time you should see the following file: '''/var/lib/e4rat/startup.log'''
  
Do not forget to remove the e4rat-collect command from your '''menu.lst''' or '''grub.cfg''' file (not necessary if you inserted it on the grub command line).
+
Do not forget to remove the e4rat-collect command from your [[Boot Loader#Configuration files|boot loader configuration file]] (not necessary if you inserted it on the grub command line).
  
 
===e4rat-realloc===
 
===e4rat-realloc===
 
For the reallocation process change to init 1
 
For the reallocation process change to init 1
 
{{bc|sudo init 1}}
 
{{bc|sudo init 1}}
{{note|Users who have switched to a pure [[systemd]] setup do not have to change [[runlevels]]. Simply login as root after running ''e4rat-collect'' on startup to run the ''e4rat-realloc'' utility after the 120 second collection process has finished.}}  
+
{{note|Users who have switched to a pure [[systemd]] setup do not have to change [[runlevels]]. Simply login as root once ''e4rat-collect'' has finished to run the ''e4rat-realloc'' utility however, switching to rescue mode in systemd with ''systemctl rescue'' may allow for more inodes/blocks to be reallocated as some may not be free while in multiuser.target}}  
 
Log in as root and run:
 
Log in as root and run:
 
{{bc|e4rat-realloc  /var/lib/e4rat/startup.log}}
 
{{bc|e4rat-realloc  /var/lib/e4rat/startup.log}}
 
This can take a while depending on how many files you have in your startup.log file.
 
This can take a while depending on how many files you have in your startup.log file.
 +
{{note|It may be worthwhile to repeat the reallocation step multiple times before exiting or rebooting in order to further reduce the fragmentation count. Simply re-run the command  a few times to see if this is possible on the your setup. If so you'll see the count number reduced after a few runs. This is perfectly safe and shouldn't cause any issues with booting.}}
  
 
===e4rat-preload===
 
===e4rat-preload===
Line 70: Line 71:
 
The savings come from
 
The savings come from
 
* using pure C with no external library dependencies, which drops the number of linked .so files from 22 to 3
 
* using pure C with no external library dependencies, which drops the number of linked .so files from 22 to 3
Note: Current [0.2.2] version of e4rat-preload is linked against 5 .so libraries, including libc, libm, libpthread ! So there is not much of a difference here !
+
{{Note|Current [0.2.3] version of e4rat-preload is linked against 5 .so libraries, including libc, libm, libpthread ! So there is not much of a difference here.}}
 
* preloading only the first 100 files (both inodes and file contents) before starting /sbin/init, then continuing to load the remaining files in parallel with the normal boot sequence.
 
* preloading only the first 100 files (both inodes and file contents) before starting /sbin/init, then continuing to load the remaining files in parallel with the normal boot sequence.
  
Line 77: Line 78:
 
Append (or replace) {{ic|1=init=/usr/sbin/e4rat-preload-lite}} permanently to your [[kernel parameters]]. Reboot and enjoy.
 
Append (or replace) {{ic|1=init=/usr/sbin/e4rat-preload-lite}} permanently to your [[kernel parameters]]. Reboot and enjoy.
  
==e4rat with different init system==
+
==e4rat with different init system, e.g. systemd==
e4rat-collect defaults to replacing itself with /sbin/init upon completion. If you need to specify another PID 1, such as /bin/systemd, you can change this in /etc/e4rat.conf by setting the '''init''' parameter and uncommenting the line.
+
e4rat-collect defaults to replacing itself with /sbin/init upon completion. If you need to specify another process with PID 1, such as '''/bin/systemd''', you can change this in '''/etc/e4rat.conf''' by setting the "init" parameter:
 +
init /bin/systemd
 +
 
 +
This allows to launch both e4rat-preload and bootchart in the same boot sequence.
  
 
==Bootchart==
 
==Bootchart==
Line 88: Line 92:
 
===bootchart 0.9-9===
 
===bootchart 0.9-9===
  
This version automatically stops logging as soon as [[Display Manager]] comes up. Supposedly the following overrides that and continues logging but it does not work for me:
+
This version of [[bootchart]] automatically stops logging as soon as [[Display Manager]] comes up. Supposedly the following overrides that and continues logging but it does not work for me:
  
 
To continue logging adjust your '''/etc/bootchartd.conf''' as follows:
 
To continue logging adjust your '''/etc/bootchartd.conf''' as follows:
Line 104: Line 108:
 
===bootchart2===
 
===bootchart2===
  
To get bootchart2 working together with e4rat edit '''/sbin/bootchartd''' and replace the line init="/sbin/init" with "init="/sbin/e4rat-preload".
+
To get [[bootchart]]2 working together with e4rat edit '''/sbin/bootchartd''' and replace the line where it says
 +
init="/sbin/init"
 +
with
 +
init="/sbin/e4rat-preload"
 +
This will allow you to measure your boot time with the fine informations that Bootchart2 provides.
  
'''/etc/bootchartd.conf''' of bootchart2 is set up differently and the line
+
It's easy to set up when to stop bootchart2 (on opposite to bootchat) by editing its configuration file '''/etc/bootchartd.conf'''. Simply adjust the line
  
 
  EXIT_PROC="kdm_greet xterm konsole gnome-terminal metacity mutter compiz ldm icewm-session enlightenment"
 
  EXIT_PROC="kdm_greet xterm konsole gnome-terminal metacity mutter compiz ldm icewm-session enlightenment"
  
can be adjusted or left empty for logging to be stopped manually rather than at a predetermined programme start.
+
with any program you want Bootchart2 stop logging when it launches, or rather left it empty for logging to be stopped manually.
  
 
==Troubleshooting==
 
==Troubleshooting==
Line 124: Line 132:
  
 
===e4rat erroneously reports an ext2 files system===
 
===e4rat erroneously reports an ext2 files system===
 
+
Add {{ic|1=rootfstype=ext4}} to [[kernel parameters]] from your bootloader.
*add the following to the kernel line in your '''grub.cfg''' or '''menu.lst'''
+
rootfstype=ext4
+
  
 
===/var/lib/e4rat/startup.log is not accessible===
 
===/var/lib/e4rat/startup.log is not accessible===

Revision as of 20:40, 11 January 2013

Summary help replacing me
How to drastically reduce boot and log-into-X time for ext4 file systems using the e4rat range of tools.
Related
Improve Boot Performance
Preload
Readahead
Ureadahead
Ext4
Forum threads
Main discussion
Improved e4rat-preload

e4rat stands for e4 'reduced access time' (ext4 file system only) and is a project by Andreas Rid and Gundolf Kiefer. The e4rat range of tools are comprised of e4rat-collect, e4rat-realloc and e4rat-preload.

Current version is 0.2.1

Process

If you look at a classical bootchart you will notice that neither disk nor CPU are utilized fully during the boot process. e4rat changes this to make full use of both disk and CPU during boot process and thus reduce boot time drastically. It consists of three stages:

  • e4rat-collect - collect files for a specified time (default 120 seconds but this can be adjusted)
  • e4rat-realloc - reallocate files
  • e4rat-preload - preload them

Who benefits, who does not

e4rat has proven to be extremely effective for typical single user set-ups which boot straight into X, perhaps even with a number of programs open. If you have a server set-up and boot only into the CLI your boot time decrease may not be as drastic. Users of SSD drives do not benefit because there are no moving parts and thus (almost) no disk latency - Ureadahead might be worth looking at.

Note: (to ureadahead users) The official e4rat manual states that ureadahead conflicts with e4rat. This may be true for Ubuntu but using e4rat in conjunction with ureadahead does work on Arch Linux, although it does not speed up the boot process any further.

It is always better to be safe than sorry. Just make backup if you cannot afford to lose data on your partition.

Installation

Install e4rat from the Official Repositories.

Getting it to work

Now for the nitty-gritty:

e4rat-collect

To have e4rat collect a list of files you will need to append init=/sbin/e4rat-collect to your kernel parameters.For example:

kernel /vmlinuz0linux root=/dev/disk/by-label/ARCH init=/sbin/e4rat-collect ro 5

This will only have to be done once so you may prefer to append this command on the grub command line itself.

Upon booting e4rat-collect will watch your system for a default of 120 seconds. So if you boot, log into X, open your favourite browser and email client all within 2 minutes, every one of those activities is logged. To change the default of 120 seconds edit /etc/e4rat.conf. To manually stop e4rat-collect type:

e4rat-collect -k
or
pkill e4rat-collect

Upon successful boot and after having waited the allotted time you should see the following file: /var/lib/e4rat/startup.log

Do not forget to remove the e4rat-collect command from your boot loader configuration file (not necessary if you inserted it on the grub command line).

e4rat-realloc

For the reallocation process change to init 1

sudo init 1
Note: Users who have switched to a pure systemd setup do not have to change runlevels. Simply login as root once e4rat-collect has finished to run the e4rat-realloc utility however, switching to rescue mode in systemd with systemctl rescue may allow for more inodes/blocks to be reallocated as some may not be free while in multiuser.target

Log in as root and run:

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

This can take a while depending on how many files you have in your startup.log file.

Note: It may be worthwhile to repeat the reallocation step multiple times before exiting or rebooting in order to further reduce the fragmentation count. Simply re-run the command a few times to see if this is possible on the your setup. If so you'll see the count number reduced after a few runs. This is perfectly safe and shouldn't cause any issues with booting.

e4rat-preload

Append init=/sbin/e4rat-preload permanently to your kernel parameters.

Alternative: e4rat-preload-lite

An alternative preload binary has been developed by jlindgren, it saves a few extra seconds from your boot time.

The savings come from

  • using pure C with no external library dependencies, which drops the number of linked .so files from 22 to 3
Note: Current [0.2.3] version of e4rat-preload is linked against 5 .so libraries, including libc, libm, libpthread ! So there is not much of a difference here.
  • preloading only the first 100 files (both inodes and file contents) before starting /sbin/init, then continuing to load the remaining files in parallel with the normal boot sequence.

You can install e4rat-preload-liteAUR from the AUR.

Append (or replace) init=/usr/sbin/e4rat-preload-lite permanently to your kernel parameters. Reboot and enjoy.

e4rat with different init system, e.g. systemd

e4rat-collect defaults to replacing itself with /sbin/init upon completion. If you need to specify another process with PID 1, such as /bin/systemd, you can change this in /etc/e4rat.conf by setting the "init" parameter:

init /bin/systemd 

This allows to launch both e4rat-preload and bootchart in the same boot sequence.

Bootchart

Note: this has not worked for and is still in development - any suggestions welcome

You will see a noticeable improvement but nothing can beat a nice Bootchart. Have it run before and after e4rat installation and gawk at the difference.

bootchart 0.9-9

This version of bootchart automatically stops logging as soon as Display Manager comes up. Supposedly the following overrides that and continues logging but it does not work for me:

To continue logging adjust your /etc/bootchartd.conf as follows:

AUTO_STOP_LOGGER="no"

To stop it manually type:

~# bootchartd stop

To run both e4rat-preload and bootchart append the following to your grub kernel line:

init=/sbin/bootchartd bootchart_init=/sbin/e4rat-preload

bootchart2

To get bootchart2 working together with e4rat edit /sbin/bootchartd and replace the line where it says

init="/sbin/init"

with

init="/sbin/e4rat-preload"

This will allow you to measure your boot time with the fine informations that Bootchart2 provides.

It's easy to set up when to stop bootchart2 (on opposite to bootchat) by editing its configuration file /etc/bootchartd.conf. Simply adjust the line

EXIT_PROC="kdm_greet xterm konsole gnome-terminal metacity mutter compiz ldm icewm-session enlightenment"

with any program you want Bootchart2 stop logging when it launches, or rather left it empty for logging to be stopped manually.

Troubleshooting

If things do not work you may want to try the following.

startup.log is not created

  • comment out auditd from your rc.conf
  • check the following for any hints
dmesg | grep e4rat
  • try to increase verbosity and loglevel to 31 in your e4rat.conf

e4rat erroneously reports an ext2 files system

Add rootfstype=ext4 to kernel parameters from your bootloader.

/var/lib/e4rat/startup.log is not accessible

  • this suggests that you have /var on a separate partition which is not yet mounted during boot. You need move your startup.log to an accessible partition (/etc/e4rat/ is just fine) and adjust your /etc/e4rat.conf to reflect this change:
startup_log_file /etc/e4rat/startup.log

Remove annoying message that mess up boot message

If you are annoyed by the e4rat-preload message during boot, decrease loglevel to 1 in /etc/e4rat.conf