Re: Async resume patch (was: Re: [GIT PULL] PM updates for 2.6.33)

Pavel Machek
2009-12-25T17:09:52Z

Hi!

> > That's partly why I realy did suggest that we do the async stuff purely in
> > the USB layer, rather than try to put it deeper in the device layer. And
> > if we do support it "natively" in the device layer like Rafael's latest
> > patch, I still think we should be very very nervous about making devices
> > async unless there is a measured - and very noticeable - advantage.
>
> Agreed. Arjan's measurements indicated that USB was one of the biggest
> offenders; everything else other than the PS/2 mouse was much faster.
> Given these results there isn't much incentive to do anything else
> asynchronously.
>
> (However other devices not present on Arjan's machine may be a
> different story. Spinning up multiple external disks is a good example
> -- although here it may be necessary for the driver to take charge,
> because spinning up a disk requires a lot of power and doing too many
> of them at the same time could be bad.)

Well, system would better be able to supply enough current... because
usb disks auto-sleep on their own, and then something like async ls -l
/*/* would kill your machine...
Pavel
--
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