Re: faster boots?

Pavel Machek
2002-04-12T11:42:53Z

Hi!

> > It works for me, 2.4.18 on HP omnibook xe3.
> >
> > You may want to watch /proc/stats to see if it is read or write
> > activity that wakes disk up.
>
> It's write activity, due to atime updates. I was using nodiratime, but
> that's not good enough because every time an executable is run a load of
> things are accessed.
>
> I found it interesting that some write activity happens almost
> immediately after the access -- and noflushd is connected in some way.
> If I do this:
>
> while :; do cat /proc/stat; sleep 1; done
>
> Then I see a few writes have occurred at nearly every iteration. I
> think that is due to the atime updates, because using "noatime" there
> are no writes at most iterations.

Well, that's no problem. noflushd stops kflushd, so it should work
even with atime. [It works for me with atimes!]

> But more interesting: I only see those few-per-second atime writes while
> noflushd is running. If I kill noflushd then they go away.

?

> I am a bit surprised that "noatime" makes a difference -- I thought that
> if noflushd spun down a disk, then pending inode writes should be
> delayed until a read or excess memory pressure forces a spin up.

Tha'ts idea behind noflushd. I don't know why it does not work for
you.

> So: "noatime" is definitely required, to spin the disk down for more
> than an instant. But even that is not good enough. I have 192MB RAM,
> btw. Is that enough to expect longer spin down times than 20s?

With noflushd, noatime should not and is not required.

Pavel
--
Casualities in World Trade Center: ~3k dead inside the building,
cryptography in U.S.A. and free speech in Czech Republic.