LPC: Booting Linux in five seconds

Posted Sep 22, 2008 19:56 UTC (Mon) by arekkusu (guest, #54092)
Parent article: LPC: Booting Linux in five seconds

Interesting Article! And impressive performance !
I am not up to the technical detail but basically it look like there are quiet a lot of optimisation to do.
I hope a lot can be done to do generalize optimisation and not just for customized for some system.
Definitely "sendmail"(...) should be be loaded by default.

I was wandering how much the SSD helped on the Eeepc. SSD should be good on boot because of the very fast access time. However the SSD on the EEPC is rather on the cheap side, not that fast compare to the high-end (100MB/s range).
If we can get those time with a cheap SSD and a pretty slow processor I can't imagine with a better SSD. And there's little doubt SSD will get more affordable and faster with time. :)

LPC: Booting Linux in five seconds

Posted Sep 22, 2008 20:32 UTC (Mon) by nix (subscriber, #2304) [Link]

Well, some disk interfaces would have ruined any chance of booting in 5s.
SCSI takes so long to start that you can start it asynchronously, but even
then it can't give you userspace (even the initramfs) until SCSI's up. (I
think it takes 10s on my machine with four disks in a rather old
sym53x875: maybe newer controllers are faster?)

More blockdev-related slowdowns that spring to mind: back in the early
2.6.20 days, the MD raid5 and raid6 code was merged. As a result the
system has to do boot-time benchmarking to find the fastest RAID-6 parity
mechanism even if you're only using RAID-5. It seems to me that md could
just start out using any old works-anywhere method, then benchmark and
switch in the background. (It has to be able to switch at runtime anyway,
or it couldn't choose among alternatives at startup like that.)

Using LVM, if you're vgscanning it is of course going to be slower than
not vgscanning: that could be sped up by simply not scanning unless you
know that the hardware has changed, and you could probably determine if
the set of available block devices has changed by digging in sysfs. (Alas
it won't tell you if some complete bastard has pulled the VG, modified it,
and put it back, but in that case the LVM cache files should *still* have
been appropriately updated, so this looks safe to me, at least as long as
the cache files exist. However if I'm wrong we're looking at big disk
corruption...)

LPC: Booting Linux in five seconds

Posted Sep 22, 2008 23:25 UTC (Mon) by jwb (guest, #15467) [Link]

I wondered the same thing. I put a Samsung SLC SSD in my ThinkPad and the cost of reading a random page is hardly any slower than the cost of reading sequential pages, so the benefit of the linear readahead is small. But it's still a lot slower than RAM, so if you can page it in ahead of time while the CPU is busy, you can still benefit.

LPC: Booting Linux in five seconds

Posted Sep 23, 2008 10:56 UTC (Tue) by spaetz (guest, #32870) [Link] (3 responses)

>Definitely "sendmail"(...) should be be loaded by default.

Why is that? Some people might want it, but many won't. I know, I don't need it.

fetchmail feature

Posted Sep 23, 2008 13:29 UTC (Tue) by dmarti (subscriber, #11625) [Link]

The Fetchmail POP client used to deliver to the system SMTP daemon by default, so you needed sendmail running before you could check your mail. Now the preferred alternative seems to be either a desktop all-in-one mail program, or OfflineIMAP.

LPC: Booting Linux in five seconds

Posted Sep 23, 2008 17:03 UTC (Tue) by s0f4r (guest, #52284) [Link] (1 responses)

Don't make 99% of all the users pay for something only you use. Sendmail does really not belong on netbooks and for those who really want to have it there: you can still start it manually. No netbook vendor should ship sendmail enabled by default.

LPC: Booting Linux in five seconds

Posted Sep 24, 2008 7:26 UTC (Wed) by ttonino (guest, #4073) [Link]

No server vendor should enable Sendmail as daemon by default either. Accepting mail on port 25 is uncommon. Sending out mail isn't, but it is done on demand with Sendmail from the command line. What cannot be sent can be pushed out with a cron job that does a sendmail -q every now and then.