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

Alan Stern
2009-12-09T15:57:06Z

On Wed, 9 Dec 2009, Linus Torvalds wrote:

> 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.)

Alan Stern