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Re: Laptop Mode

On Mon, Sep 13 2004, Daniel Kobras wrote:
> On Mon, Sep 13, 2004 at 08:16:09AM +0200, Jens Axboe wrote:
> > On Sun, Sep 12 2004, Bryan Forbes wrote:
> > > 1. What's the difference between that and noflushd?
> > 
> > noflushd is dumb, 
> Heh, don't call the baby dumb. It's had a difficult childhood; evil
> parents that didn't care. No, really, a bit retarded maybe...


> > it just tries to postpone writes. laptop mode is more
> > involved, the vm knows when the computer is in laptop mode.
> > additionally, laptop mode can do things like automatic flushing of dirty
> > data when you spin your drive up for other activity.
> The latter being included in noflushd as well. It comes with a few more

How does that work reliably?

> fancy feature like different policies per disk, optionally preventing
> spindown when machine is used interactively, etc. Oh, and it works with
> kernels that predate the laptop-mode patch. The ordinary laptop user
> won't care, and is usually better off with laptop-mode these days.

Sounds useful. laptop mode support in kernel should only do the
absolutely necessary, like spin-up detection. You should adapt your
stuff to laptop mode.

The noflushd approach was never very clean imho, it was a case of 'this
is where we can do it with a hook' and not designed in place.

Jens Axboe

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