From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 251AE407 for ; Fri, 24 Jul 2015 22:05:56 +0000 (UTC) Received: from v094114.home.net.pl (v094114.home.net.pl [79.96.170.134]) by smtp1.linuxfoundation.org (Postfix) with SMTP id 2693E8D for ; Fri, 24 Jul 2015 22:05:54 +0000 (UTC) From: "Rafael J. Wysocki" To: ksummit-discuss@lists.linuxfoundation.org Date: Sat, 25 Jul 2015 00:26:03 +0200 Message-ID: <8734973.3SWuCLvkiU@vostro.rjw.lan> In-Reply-To: <20150724060049.GX10928@atomide.com> References: <20150723105726.GC30929@amd> <20150724143427.5a045528@noble> <20150724060049.GX10928@atomide.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="utf-8" Cc: Bjorn Andersson , riverful.kim@samsung.com, kyungmin.park@samsung.com, John Stultz , Pavel Machek Subject: Re: [Ksummit-discuss] [CORE TOPIC] Mainline kernel on a cellphone List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Thursday, July 23, 2015 11:00:49 PM Tony Lindgren wrote: > * NeilBrown [150723 21:37]: > > On Thu, 23 Jul 2015 22:34:29 +0200 Pavel Machek wrote: > > > > > > and the big one... for Android people (not me): > > > > > > 6) do we need to use s2ram (and then pretend phone is not suspended) > > > to save power on cellphones? If so, do we need new interface for > > > applications to signal "I'd really like to run"? > > > > > > > For the first half of this question, the answer is: > > Probably not. runtime-pm should be able to put all devices to sleep, > > and cgroup freezer should be able to freeze untrusted processes. > > Yes s2ram is just an additional tool. PM runtime alone can > already provide a reasonable battery life for a phone as long as > it's properly implemented and the hardware supports it. With > reasonable battery life in this case I mean over 10 days in idle > mode with system running and timers working. > > > But I suspect runtime-pm doesn't provide as much power saving as > > system suspend, and using the cgroup freezer means lots of changes to > > userspace. > > So lots of work would be needed to meet this goal, if it is a > > worthwhile goal. > > And with s2ram the difference is that then the system is not running > and timers don't work so it really needs to be optional. Right. Even with suspend-to-idle we can get less energy usage with respect to runtime idle (device runtime PM plus cpuidle) just because timer events are disabled then. > > For the second half - it is really a user-space problem. User-space > > decides when to enter suspend. > > (or CONFIG_PM_WAKELOCKS can enable a kernel interface > > via /sys/power/wake_lock). > > Yeah agreed. Right. Thanks, Rafael