From: Beata Michalska <beata.michalska@arm.com>
To: Sumit Gupta <sumitg@nvidia.com>
Cc: linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, ionela.voinescu@arm.com,
vanshikonda@os.amperecomputing.com, sudeep.holla@arm.com,
will@kernel.org, catalin.marinas@arm.com,
vincent.guittot@linaro.org, yang@os.amperecomputing.com,
lihuisong@huawei.com, linux-tegra <linux-tegra@vger.kernel.org>
Subject: Re: [PATCH v4 3/4] arm64: Update AMU-based frequency scale factor on entering idle
Date: Thu, 11 Apr 2024 21:30:16 +0200 [thread overview]
Message-ID: <Zhg6SLfqrRUf0vmp@arm.com> (raw)
In-Reply-To: <3ab3cbc1-234f-e0b6-4521-298018547aad@nvidia.com>
On Thu, Apr 11, 2024 at 12:27:00AM +0530, Sumit Gupta wrote:
Hi Sumit,
> Hi Beata,
>
> This patch is giving abort due to 'amu_fie_cpus' mask which gets allocated
> later in 'init_amu_fie()'.
>
> ] smp: Bringing up secondary CPUs ...
> ] Unable to handle kernel read from unreadable memory at virtual
> address 0000000000000000
> .......
> ] Call trace:
> ] arch_cpu_idle_enter+0x30/0xe0
> ] do_idle+0xb8/0x2e0
> ] cpu_startup_entry+0x3c/0x50
> ] rest_init+0x108/0x128
> ] start_kernel+0x7a4/0xa50
> ] __primary_switched+0x80/0x90
> ] Code: d53cd042 b8626800 f943c821 53067c02 (f8627821)
> ] ---[ end trace 0000000000000000 ]---
> ] Kernel panic - not syncing: Oops: Fatal exception
>
> Added cpumask_available() check before access to fix.
>
> +++ b/arch/arm64/kernel/topology.c
> @@ -211,9 +211,13 @@ void arch_cpu_idle_enter(void)
> {
> unsigned int cpu = smp_processor_id();
>
> - if (!cpumask_test_cpu(cpu, amu_fie_cpus))
> + if (cpumask_available(amu_fie_cpus) &&
> + !cpumask_test_cpu(cpu, amu_fie_cpus))
> return;
>
That's actually a gruesome mistake on my side. Thanks for catching that one.
On that note: arch_freq_get_on_cpu should be also protected case amu fie init
fails for some reason. Will be sending an update.
Thanks again.
---
BR
Beata
> Thank you,
> Sumit Gupta
>
> On 05/04/24 19:03, Beata Michalska wrote:
> > External email: Use caution opening links or attachments
> >
> >
> > Now that the frequency scale factor has been activated for retrieving
> > current frequency on a given CPU, trigger its update upon entering
> > idle. This will, to an extent, allow querying last known frequency
> > in a non-invasive way. It will also improve the frequency scale factor
> > accuracy when a CPU entering idle did not receive a tick for a while.
> > As a consequence, for idle cores, the reported frequency will be the
> > last one observed before entering the idle state.
> >
> > Suggested-by: Vanshidhar Konda <vanshikonda@os.amperecomputing.com>
> > Signed-off-by: Beata Michalska <beata.michalska@arm.com>
> > ---
> > arch/arm64/kernel/topology.c | 17 +++++++++++++++--
> > 1 file changed, 15 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
> > index b03fe8617721..f204f6489f98 100644
> > --- a/arch/arm64/kernel/topology.c
> > +++ b/arch/arm64/kernel/topology.c
> > @@ -207,6 +207,19 @@ static struct scale_freq_data amu_sfd = {
> > .set_freq_scale = amu_scale_freq_tick,
> > };
> >
> > +void arch_cpu_idle_enter(void)
> > +{
> > + unsigned int cpu = smp_processor_id();
> > +
> > + if (!cpumask_test_cpu(cpu, amu_fie_cpus))
> > + return;
> > +
> > + /* Kick in AMU update but only if one has not happened already */
> > + if (housekeeping_cpu(cpu, HK_TYPE_TICK) &&
> > + time_is_before_jiffies(per_cpu(cpu_amu_samples.last_update, cpu)))
> > + amu_scale_freq_tick();
> > +}
> > +
> > #define AMU_SAMPLE_EXP_MS 20
> >
> > unsigned int arch_freq_get_on_cpu(int cpu)
> > @@ -232,8 +245,8 @@ unsigned int arch_freq_get_on_cpu(int cpu)
> > * this boils down to identifying an active cpu within the same freq
> > * domain, if any.
> > */
> > - if (!housekeeping_cpu(cpu, HK_TYPE_TICK) ||
> > - time_is_before_jiffies(last_update + msecs_to_jiffies(AMU_SAMPLE_EXP_MS))) {
> > + if (!housekeeping_cpu(cpu, HK_TYPE_TICK) || (!idle_cpu(cpu) &&
> > + time_is_before_jiffies(last_update + msecs_to_jiffies(AMU_SAMPLE_EXP_MS)))) {
> > struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
> > int ref_cpu = cpu;
> >
> > --
> > 2.25.1
> >
prev parent reply other threads:[~2024-04-11 19:30 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20240405133319.859813-1-beata.michalska@arm.com>
[not found] ` <20240405133319.859813-4-beata.michalska@arm.com>
2024-04-10 18:57 ` [PATCH v4 3/4] arm64: Update AMU-based frequency scale factor on entering idle Sumit Gupta
2024-04-11 19:30 ` Beata Michalska [this message]
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