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Message-ID: <20091225170943.GB1581@ucw.cz>
Date: Fri, 25 Dec 2009 18:09:44 +0100
From: Pavel Machek <pavel@....cz>
To: Alan Stern <stern@...land.harvard.edu>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
"Rafael J. Wysocki" <rjw@...k.pl>, Zhang Rui <rui.zhang@...el.com>,
LKML <linux-kernel@...r.kernel.org>,
ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
pm list <linux-pm@...ts.linux-foundation.org>
Subject: Re: Async resume patch (was: Re: [GIT PULL] PM updates for 2.6.33)
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
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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