Harald Hoyer wrote:
http://www.harald-hoyer.de/personal/blog/fedora-10-boot-analysis
A brief Fedora 10 boot analysis.
Hardware: Asus EeePC 901 with a flash disk.
Time taken from entering the encrypted root disk password until the password can be entered (after pressing return in gdm). The 10 second wait in nash is ignored here (which really annoys me and should be configurable in /etc/sysconfig/mkinitrd).
Default Live CD Installation: 39s (bootchart http://www.harald-hoyer.de/files/f10boot/bootchart-nonread.png)
After installing readahead and running one collection boot process: 36s (bootchart http://www.harald-hoyer.de/files/f10boot/bootchart-readahead.png)
At this point, I recognized that all processes (NetworkManager and newaliases), which call a fsync(), let the boot process wait until all data is written to disk. This is the same effect as the firefox sqlite fsync bug http://shaver.off.net/diary/2008/05/25/fsyncers-and-curveballs/.
Mounting the root filessystem with relatime and turning off ordered data writing for the journal with
# tune2fs -o journal_data_writeback /dev/root
improved the situation (even though data might be old on the disk after a crash, but ext3 does not force the disk to empty the write cache anyway).
Turning off setroubleshoot and fixing https://bugzilla.redhat.com/show_bug.cgi?id=476023 and https://bugzilla.redhat.com/show_bug.cgi?id=476028: 32s (bootchart http://www.harald-hoyer.de/files/f10boot/bootchart-readahead-nosetrouble.png)
Turning off bootchart: 30s
So all in all we have nearly accomplished the 30 Second Startup Feature http://fedoraproject.org/wiki/Features/30SecondStartup.
Well, no; not if this requires data=writeback. We can't ship that way, it's a potential security hole. You don't want someone's maildir suddenly containing pieces of /etc/shadow or whatnot. The old data that may be exposed by data=writeback may not belong to that user.
-Eric