spindown [was Re: 2.4.6-pre2, pre3 VM Behavior]

[Pavel Machek]

Hi!

> Roger> It does if you are running on a laptop. Then you do not want
> Roger> the pages go out all the time. Disk has gone too sleep, needs
> Roger> to start to write a few pages, stays idle for a while, goes to
> Roger> sleep, a few more pages, ...
> 
> That could be handled by a metric which says if the disk is spun down,
> wait until there is more memory pressure before writing.  But if the
> disk is spinning, we don't care, you should start writing out buffers
> at some low rate to keep the pressure from rising too rapidly.  

Notice that write is not free (in terms of power) even if disk is spinning.
Seeks (etc) also take some power. And think about flashcards. It certainly
is cheaper tha spinning disk up but still not free.

Also note that kernel does not [currently] know that disks went spindown.
                                                                Pavel
-- 
Philips Velo 1: 1"x4"x8", 300gram, 60, 12MB, 40bogomips, linux, mutt,
details at http://atrey.karlin.mff.cuni.cz/~pavel/velo/index.html.

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/