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 2FB5E93E for ; Thu, 16 Jul 2015 15:45:10 +0000 (UTC) Received: from mail-yk0-f170.google.com (mail-yk0-f170.google.com [209.85.160.170]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 2B21524A for ; Thu, 16 Jul 2015 15:45:08 +0000 (UTC) Received: by ykeo3 with SMTP id o3so67155739yke.0 for ; Thu, 16 Jul 2015 08:45:07 -0700 (PDT) MIME-Version: 1.0 References: <1489458.8WDRattPkl@vostro.rjw.lan> <1455994.zAMIqEIJx2@vostro.rjw.lan> <2869041.AWiygZspUy@vostro.rjw.lan> <20150716011056.GA8931@x> <1437038341.6856.22.camel@infradead.org> In-Reply-To: <1437038341.6856.22.camel@infradead.org> From: Kristen Accardi Date: Thu, 16 Jul 2015 15:44:57 +0000 Message-ID: To: David Woodhouse , Josh Triplett , "Rafael J. Wysocki" Content-Type: multipart/alternative; boundary=001a1142d786acc6f9051afff4ec Cc: Grant Likely , "Brown, Len" , Alan Stern , "ksummit-discuss@lists.linuxfoundation.org" , Kristen Carlson Accardi Subject: Re: [Ksummit-discuss] [TECH TOPIC] System-wide interface to specify the level of PM tuning List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , --001a1142d786acc6f9051afff4ec Content-Type: text/plain; charset=UTF-8 On Thu, Jul 16, 2015 at 2:19 AM David Woodhouse wrote: > On Wed, 2015-07-15 at 18:10 -0700, Josh Triplett wrote: > > > > > The point here is whether or not we want to have a way to make all of > them be > > > enabled by default instead and see what happens, for example. > > > > To some degree that seems like an admission of defeat: we can't possibly > > do the right thing by default, so we give up and add a way for the user > > to configure it. > > > > We should be selecting the most sensible combination of power and > > performance by default; we should not punt that question to the average > > user, *or* to the distros. > > Not to the user, perhaps. But it's not *so* unreasonable to let each of > the distros tune things for *their* class of users. We might want base > profiles for 'server', 'desktop' and 'laptop on battery' that distros > work from. > > We need to be able to give even the distros more help than they have now. The problem is that the distros simply don't have the knowledge to tune *all* the knobs appropriately. If we gave them one knob as you suggested (and what Rafael is suggesting) set to a sane default determined by the kernel - they could then use whatever userspace tool to change it based on whatever parameters they want. But although that's complex, it's not the real problem. > > The real problem, as others have said, is when we have power management > features which work fine for 99% of the population, but fail > occasionally on broken hardware. > > We can't easily blacklist the known-broken devices or whitelist the > good ones, and we end up having to turn the feature off by default. > > Sure, a DMI match on "HP" and "TO BE FILLED BY OEM" would often go a > long way for a certain class of problem, but even that's not sufficient > :) > driver maintainers don't want to maintain blacklist/whitelist because it's hard. It'd be nice to be able to load a black list or white list of devices from the filesystem like we do with firmware. > > --001a1142d786acc6f9051afff4ec Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
On Thu, Jul 16= , 2015 at 2:19 AM David Woodhouse <dwmw2@infradead.org> wrote:
But although that's complex, it's not the real problem.

The real problem, as others have said, is when we have power management
features which work fine for 99% of the population, but fail
occasionally on broken hardware.

We can't easily blacklist the known-broken devices or whitelist the
good ones, and we end up having to turn the feature off by default.

Sure, a DMI match on "HP" and "TO BE FILLED BY OEM" wou= ld often go a
long way for a certain class of problem, but even that's not sufficient=
:)

driver maintainers don't want to= maintain blacklist/whitelist because it's hard.=C2=A0 It'd be nice= to be able to load a black list or white list of devices from the filesyst= em like we do with firmware.

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