linux-kernel - Re: [PATCH 0/8] Suspend block api (version 7)

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <87tyq5qj3v.fsf@deeprootsystems.com>
Date:	Tue, 18 May 2010 09:18:12 -0700
From:	Kevin Hilman <khilman@...prootsystems.com>
To:	Arve Hjønnevåg <arve@...roid.com>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	linux-pm@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
	Greg KH <gregkh@...e.de>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Alan Stern <stern@...land.harvard.edu>,
	Brian Swetland <swetland@...gle.com>,
	Daniel Walker <dwalker@...o99.com>,
	"Theodore Ts'o" <tytso@....edu>, Matthew Garrett <mjg@...hat.com>
Subject: Re: [PATCH 0/8] Suspend block api (version 7)

Arve Hjønnevåg <arve@...roid.com> writes:

>
> PM: Opportunistic suspend support.
>
> Power management features present in the current mainline kernel are
> insufficient to get maximum possible energy savings on some platforms,
> such as Android, because low power states can only safely be entered
> from idle.  Suspend, in its current form, cannot be used, since wakeup
> events that occur right after initiating suspend will not be processed
> until another possibly unrelated event wake up the system again.

I think the problems with wakeups in the current suspend path need to
be described in more detail.  In particular, why check_wakeup_irqs()
is not enough etc.

> On some systems idle combined with runtime PM can enter the same power
> state as suspend, but periodic wakeups increase the average power
> consumption. Suspending the system also reduces the harm caused by
> apps that never go idle. On other systems suspend can enter a much
> lower power state than idle.
>
> To allow Android and similar platforms to save more energy than they
> currently can save using the mainline kernel, we introduce a mechanism
> by which the system is automatically suspended (i.e. put into a
> system-wide sleep state) whenever it's not doing useful work, called
> opportunistic suspend.

A definition of "useful work" here would provide clarity and would
also help clarify by what criteria other on-going work is determined
to be not useful.

Kevin
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/