linux-kernel - Re: [linux-pm] [PATCH 0/8] Suspend block api (version 8)

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Date:	Thu, 27 May 2010 16:50:36 -0700
From:	Arve Hjønnevåg <arve@...roid.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Alan Stern <stern@...land.harvard.edu>,
	Felipe Balbi <felipe.balbi@...ia.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"Paul@...p1.linux-foundation.org" <Paul@...p1.linux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Florian Mickler <florian@...kler.org>,
	Linux OMAP Mailing List <linux-omap@...r.kernel.org>,
	Linux PM <linux-pm@...ts.linux-foundation.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [linux-pm] [PATCH 0/8] Suspend block api (version 8)

On Thu, May 27, 2010 at 4:43 PM, Rafael J. Wysocki <rjw@...k.pl> wrote:
> On Thursday 27 May 2010, Thomas Gleixner wrote:
>> On Thu, 27 May 2010, Rafael J. Wysocki wrote:
>>
>> > On Thursday 27 May 2010, Thomas Gleixner wrote:
>> > > On Thu, 27 May 2010, Alan Stern wrote:
>> > >
>> > > > On Thu, 27 May 2010, Felipe Balbi wrote:
>> > > >
>> > > > > On Thu, May 27, 2010 at 05:06:23PM +0200, ext Alan Stern wrote:
>> > > > > >If people don't mind, here is a greatly simplified summary of the
>> > > > > >comments and objections I have seen so far on this thread:
>> > > > > >
>> > > > > >     The in-kernel suspend blocker implementation is okay, even
>> > > > > >     beneficial.
>> > > > >
>> > > > > I disagree here. I believe expressing that as QoS is much better. Let
>> > > > > the kernel decide which power state is better as long as I can say I
>> > > > > need 100us IRQ latency or 100ms wakeup latency.
>> > > >
>> > > > Does this mean you believe "echo mem >/sys/power/state" is bad and
>> > > > should be removed?  Or "echo disk >/sys/power/state"?  They pay no
>> > >
>> > > mem should be replaced by an idle suspend to ram mechanism
>> >
>> > Well, what about when I want the machine to suspend _regardless_ of whether
>> > or not it's idle at the moment?  That actually happens quite often to me. :-)
>>
>> Fair enough. Let's agree on a non ambigous terminology then:
>>
>>      forced:
>>
>>            suspend which you enforce via user interaction, which
>>            also implies that you risk losing wakeups depending on
>>            the hardware properties
>
> OK
>
>>      opportunistic:
>>
>>            suspend driven from the idle context, which guarantees to
>>            not lose wakeups. Provided only when the hardware does
>>            provide the necessary capabilities.
>
> I can accept that definition, but this is not what "opportunistic" means in the

Is there a difference between this new definition of opportunistic and
idle? I assume suspend here means low a low power sleep state since it
is impossible to initiate and abort Linux suspend from idle since
initiating suspend will cause the system to become not idle.

> Arve's changelogs.  What it means there is that he wants the system to suspend
> even when it is not technically idle (like in the updatedb example I gave in a
> previous message).  Suspend blockers are supposed to be a mechanism by which
> the kernel and user space together may determine when to suspend (and it's
> somewhat orthogonal to idle).
>



-- 
Arve Hjønnevåg
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