Improve (potentially halve) login time by using readahead

[brazzmonkey]

hi jdong,
i have 2gb of RAM. surely i removed the biggest files as you advised to (there was a few files ranging from 10mb to 35mb), no big deal, though.

i don't know why there are so many other files cached, especially files i barely use (nvidia-settings, ktorrent for instance). they're not loaded during login so i don't understand why readahead would cache them.

[jdong]

hi jdong,
i have 2gb of RAM. surely i removed the biggest files as you advised to (there was a few files ranging from 10mb to 35mb), no big deal, though.

i don't know why there are so many other files cached, especially files i barely use (nvidia-settings, ktorrent for instance). they're not loaded during login so i don't understand why readahead would cache them.

That's pretty odd... Are you sure between the time you started readahead-watch and logging in, there wasn't anything running in the background that was accessing the disk? Could just be bad luck and the profiling caught a flurry of background activity.

[brazzmonkey]

yes, i'm sure there was no background activity.
FYI, i use kubuntu 7.04, if that matters.

attached you'll find the output of the sorting command, for my / (i have a dedicated partition for /home, too).
you'll see there quite a bunch of files which are to be cached (some are very big, indeed…).

i suspect some files are already being cached while logging in, that would explain why there are so many references to programs that are not running…

one advice when caching files from /home : empty your trash bin before caching, or remove any reference to trashed files beforehand.

just my € 0.02.

[foxy123]

I have upgraded to Gutsy and tried this method (in Feisty I just used to do profiling during the boot). In Feisty I could boot up in 35-37 sec but now it is 1 min, even after the optimisation from this thread. I have attached my bootcharts from both Feisty and Gutsy.

[DDM]

According to bootchart, readahead actually COSTS me 10 seconds on my desktop using Gutsy. I'll try the process again and hopefully it'll work.

[jdong]

Bootchart does not always reflect actual boot times you experience as a user (GDM is spawned at S13, while bootchart is stopped at S99) -- use the old-fashioned stopwatch method to time your bootups

[DDM]

Yeah I realized after I posted it that I wasn't accounting for post-gdm times. Anyways, this did wonders for my 2 year old laptop, not so much for my pretty new desktop.

[jdong]

The faster seek-times your disk has, and the more heuristics your disk has to minimize seeking when given a huge number of IO Requests, the less this hack will do.

(Note specifically relating to the rc.local hack, bootchart will count all of the GNOME prefetching towards the boottime, which of course will inflate that number)

[Hakimio]

I have the same problem as brazzmonkey has.
No background activity (even prevented tracker from starting and removed all the icons from the desktop) and the file is REALLY BIG. I am using Ubuntu 7.04.
I have attached the generated file.
BTW: I have 1GB of RAM.

[JSorrell]

Your guide didn't halve my login time. It eliminated it almost entirely. I went from upwards of 10 seconds or more to roughly one second. This is with 2 gigs of RAM.

Absolutely fantastic.