linux-kernel - Re: [PATCH v10 1/3] cpufreq: Add mechanism for registering utilization update callbacks

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 for Android: free password hash cracker in your pocket

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

Message-ID: <CAJZ5v0gs3bddvskseh58q+0d+KqXYt=4SYGuiR3vdhdOyhoKmA@mail.gmail.com>
Date:	Mon, 22 Feb 2016 22:26:47 +0100
From:	"Rafael J. Wysocki" <rafael@...nel.org>
To:	Juri Lelli <juri.lelli@....com>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Steve Muckle <steve.muckle@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v10 1/3] cpufreq: Add mechanism for registering
 utilization update callbacks

On Mon, Feb 22, 2016 at 10:32 AM, Juri Lelli <juri.lelli@....com> wrote:
> On 19/02/16 23:14, Rafael J. Wysocki wrote:
>> On Friday, February 19, 2016 08:09:17 AM Juri Lelli wrote:
>> > Hi Rafael,
>> >
>> > On 18/02/16 21:22, Rafael J. Wysocki wrote:
>> > > On Mon, Feb 15, 2016 at 10:47 PM, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
>> > > > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>> > > >

[cut]

>> That said, if the concern is that there are plans to change the way the
>> scheduler computes the utilization numbers and that may become difficult to
>> carry out if cpufreq starts to depend on them in their current form, then I
>> may agree that it is valid, but I'm not aware of those plans ATM.
>>
>
> No, I don't think there's any substantial discussion going on about the
> utilization numbers.

OK, so the statement below applies.

>> However, if the numbers are going to stay what they are, I don't see why
>> passing them to cpufreq may possibly become problematic at any point.
>
> My concern was mostly on the fact that there is already another RFC
> under discussion that uses the same numbers and has different hooks
> placed in scheduler code (Steve's sched-freq); so, additional hooks
> might generate confusion, IMHO.

So this is about the hooks rather than about their arguments after
all, isn't it?

I fail to see why it is better to drop the arguments and leave the hooks, then.

OTOH, I see reasons for keeping the arguments along with the hooks,
but let me address that in my next reply.

Now, if the call sites of the hooks change in the future, it won't be
a problem for me as long as the new hooks are invoked on a regular
basis or, if they aren't, as long as I can figure out from the
arguments they pass that I should not expect an update any time soon.

If the arguments change, it won't be a problem either as long as they
are sufficient to be inserted into the frequency selection formula
used by the schedutil governor I posted and produce sensible
frequencies for the CPU.

Thanks,
Rafael