From: Ionela Voinescu <ionela.voinescu@arm.com>
To: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>,
rjw@rjwysocki.net, catalin.marinas@arm.com, sudeep.holla@arm.com,
will@kernel.org, linux@armlinux.org.uk, mingo@redhat.com,
peterz@infradead.org, linux-pm@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 3/7] arch_topology: disable frequency invariance for CONFIG_BL_SWITCHER
Date: Mon, 10 Aug 2020 10:01:00 +0100 [thread overview]
Message-ID: <20200810090100.GA7190@arm.com> (raw)
In-Reply-To: <20200804063046.a2hw5cxwiewhb3aw@vireshk-mac-ubuntu>
Hi guys,
On Tuesday 04 Aug 2020 at 12:00:46 (+0530), Viresh Kumar wrote:
> On 30-07-20, 12:29, Dietmar Eggemann wrote:
> > On 30/07/2020 06:24, Viresh Kumar wrote:
> > > On 22-07-20, 10:37, Ionela Voinescu wrote:
> > >> +++ b/drivers/base/arch_topology.c
> > >> @@ -27,6 +27,7 @@ __weak bool arch_freq_counters_available(struct cpumask *cpus)
> > >> }
> > >> DEFINE_PER_CPU(unsigned long, freq_scale) = SCHED_CAPACITY_SCALE;
> > >>
> > >> +#ifndef CONFIG_BL_SWITCHER
> > >> void arch_set_freq_scale(struct cpumask *cpus, unsigned long cur_freq,
> > >> unsigned long max_freq)
> > >> {
> > >> @@ -46,6 +47,7 @@ void arch_set_freq_scale(struct cpumask *cpus, unsigned long cur_freq,
> > >> for_each_cpu(i, cpus)
> > >> per_cpu(freq_scale, i) = scale;
> > >> }
> > >> +#endif
> > >
> > > I don't really like this change, the ifdef hackery is disgusting and
> > > then we are putting that in a completely different part of the kernel.
> > >
> > > There are at least these two ways of solving this, maybe more:
> > >
> > > - Fix the bl switcher driver and add the complexity in it (which you
> > > tried to do earlier).
> > >
> > > - Add a cpufreq flag to skip arch-set-freq-scale call.
> >
> > I agree it's not nice but IMHO the cpufreq flag is worse since we would
> > introduce new infrastructure only for a deprecated feature. I'm assuming
> > that BL SWITCHER is the only feature needing this CPUfreq flag extension.
> >
> > #ifdef CONFIG_BL_SWITCHER is already in drivers/irqchip/irq-gic.c so
> > it's ugly already.
> >
> > Runtime detecting (via bL_switching_enabled) of BL SWITCHER is right now
> > also only handled inside vexpress-spc-cpufreq.c via a
> > bL_switcher_notifier. A mechanism which also sits behind a #ifdef
> > CONFIG_BL_SWITCHER.
>
> Vexpress one is a driver and so ugliness could be ignored here :)
>
> So here is option number 3 (in continuation of the earlier two
> options):
> - Don't do anything for bL switcher, just add a TODO/NOTE in the
> driver that FIE is broken for switcher. And I don't think anyone
> will care about FIE for the switcher anyway :)
>
I gave it a bit of time in case anyone had strong opinions about this,
but given the lack of those, what I can do in this series is the
following: ignore the problem :). This issue was there before these
patches and it will continue to be there after these patches - nothing
changes.
Separately from this series, I can submit a patch with Viresh's
suggestion above and we can spin around a bit discussing this, if there
is interest. My opinion on this is that option 1 is ugly but it does fix
an issue in a relatively non-invasive way. I agree with "I don't think
anyone will care about FIE for the switcher anyway", but for me this
means that nobody will care if it's supported (and therefore option 1
is the proper solution). But if bL switcher is used, I think people might
care if it's broken, as it results in incorrect scheduler signals.
Therefore, I would not like leaving it broken (option 3). If it's not
used, option 2 is obvious.
Many thanks,
Ionela.
> --
> viresh
next prev parent reply other threads:[~2020-08-10 9:01 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-22 9:37 [PATCH v2 0/7] cpufreq: improve frequency invariance support Ionela Voinescu
2020-07-22 9:37 ` [PATCH v2 1/7] cpufreq: move invariance setter calls in cpufreq core Ionela Voinescu
2020-07-27 13:48 ` Rafael J. Wysocki
2020-07-29 9:03 ` Ionela Voinescu
2020-07-30 3:41 ` Viresh Kumar
2020-08-03 13:26 ` Ionela Voinescu
2020-08-03 13:46 ` Rafael J. Wysocki
2020-08-03 14:16 ` Ionela Voinescu
2020-07-22 9:37 ` [PATCH v2 2/7] cpufreq: set invariance scale factor on transition end Ionela Voinescu
2020-07-27 13:52 ` Rafael J. Wysocki
2020-07-29 9:14 ` Ionela Voinescu
2020-07-30 4:13 ` Viresh Kumar
2020-08-03 13:58 ` Ionela Voinescu
2020-08-04 6:26 ` Viresh Kumar
2020-08-05 10:35 ` Ionela Voinescu
2020-07-22 9:37 ` [PATCH v2 3/7] arch_topology: disable frequency invariance for CONFIG_BL_SWITCHER Ionela Voinescu
2020-07-30 4:24 ` Viresh Kumar
2020-07-30 10:29 ` Dietmar Eggemann
2020-07-31 15:48 ` Sudeep Holla
2020-08-03 14:39 ` Ionela Voinescu
2020-08-04 6:30 ` Viresh Kumar
2020-08-10 9:01 ` Ionela Voinescu [this message]
2020-07-22 9:37 ` [PATCH v2 4/7] cpufreq: report whether cpufreq supports Frequency Invariance (FI) Ionela Voinescu
2020-07-27 14:02 ` Rafael J. Wysocki
2020-07-29 14:39 ` Ionela Voinescu
2020-07-30 4:43 ` Viresh Kumar
2020-08-03 15:24 ` Ionela Voinescu
2020-08-04 6:46 ` Viresh Kumar
2020-08-05 10:35 ` Ionela Voinescu
2020-07-22 9:37 ` [PATCH v2 5/7] arch_topology,cpufreq,sched/core: constify arch_* cpumasks Ionela Voinescu
2020-07-30 11:43 ` Catalin Marinas
2020-07-22 9:37 ` [PATCH v2 6/7] arch_topology,arm,arm64: define arch_scale_freq_invariant() Ionela Voinescu
2020-07-30 11:44 ` Catalin Marinas
2020-07-22 9:37 ` [PATCH v2 7/7] cpufreq: make schedutil the default for arm and arm64 Ionela Voinescu
2020-07-30 4:54 ` Viresh Kumar
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200810090100.GA7190@arm.com \
--to=ionela.voinescu@arm.com \
--cc=catalin.marinas@arm.com \
--cc=dietmar.eggemann@arm.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-pm@vger.kernel.org \
--cc=linux@armlinux.org.uk \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=rjw@rjwysocki.net \
--cc=sudeep.holla@arm.com \
--cc=viresh.kumar@linaro.org \
--cc=will@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).