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From: Valentin Schneider <valentin.schneider@arm.com>
To: Suzuki Kuruppassery Poulose <suzuki.poulose@arm.com>,
	Ionela Voinescu <ionela.voinescu@arm.com>,
	catalin.marinas@arm.com, will@kernel.org, mark.rutland@arm.com,
	maz@kernel.org, sudeep.holla@arm.com, lukasz.luba@arm.com,
	rjw@rjwysocki.net
Cc: peterz@infradead.org, mingo@redhat.com,
	vincent.guittot@linaro.org, viresh.kumar@linaro.org,
	linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org
Subject: Re: [PATCH v3 1/7] arm64: add support for the AMU extension v1
Date: Wed, 12 Feb 2020 14:54:45 +0000	[thread overview]
Message-ID: <b2b640ac-0cc3-b09e-1f6c-f01234295b3b@arm.com> (raw)
In-Reply-To: <93472f17-6465-641d-ea82-3230b5697ffd@arm.com>

On 12/02/2020 11:30, Suzuki Kuruppassery Poulose wrote:
>> +static bool has_amu(const struct arm64_cpu_capabilities *cap,
>> +               int __unused)
>> +{
>> +    /*
>> +     * The AMU extension is a non-conflicting feature: the kernel can
>> +     * safely run a mix of CPUs with and without support for the
>> +     * activity monitors extension. Therefore, if not disabled through
>> +     * the kernel command line early parameter, enable the capability
>> +     * to allow any late CPU to use the feature.
>> +     *
>> +     * With this feature enabled, the cpu_enable function will be called
>> +     * for all CPUs that match the criteria, including secondary and
>> +     * hotplugged, marking this feature as present on that respective CPU.
>> +     * The enable function will also print a detection message.
>> +     */
>> +
>> +    if (!disable_amu && !zalloc_cpumask_var(&amu_cpus, GFP_KERNEL)) {
> 
> This looks problematic. Don't we end up in allocating the memory during
> "each CPU" check and thus leaking memory ? Do we really need to allocate
> this dynamically ?
> 

For the static vs dynamic thing, I think it's not *too* important here since
we don't risk pwning the stack because of the cpumask. That said, if we are
somewhat pedantic about memory usage, the static allocation is done
against NR_CPUS whereas the dynamic one is done against nr_cpu_ids.
Pretty inconsequential for a single cpumask, but I guess it all adds up
eventually...

  reply	other threads:[~2020-02-12 14:54 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-11 18:45 [PATCH v3 0/7] arm64: ARMv8.4 Activity Monitors support Ionela Voinescu
2020-02-11 18:45 ` [PATCH v3 1/7] arm64: add support for the AMU extension v1 Ionela Voinescu
2020-02-12 11:30   ` Suzuki Kuruppassery Poulose
2020-02-12 14:54     ` Valentin Schneider [this message]
2020-02-12 16:10     ` Ionela Voinescu
2020-02-12 16:20       ` Suzuki Kuruppassery Poulose
2020-02-12 18:20         ` Ionela Voinescu
2020-02-12 19:24           ` Suzuki K Poulose
2020-02-12 20:19         ` Ionela Voinescu
2020-02-12 16:24       ` Vladimir Murzin
2020-02-12 18:27         ` Ionela Voinescu
2020-02-11 18:45 ` [PATCH v3 2/7] arm64: trap to EL1 accesses to AMU counters from EL0 Ionela Voinescu
2020-02-12 11:44   ` Suzuki Kuruppassery Poulose
2020-02-12 15:36   ` Valentin Schneider
2020-02-11 18:45 ` [PATCH v3 3/7] arm64/kvm: disable access to AMU registers from kvm guests Ionela Voinescu
2020-02-12 15:36   ` Valentin Schneider
2020-02-12 16:33   ` Suzuki Kuruppassery Poulose
2020-02-11 18:45 ` [PATCH v3 4/7] Documentation: arm64: document support for the AMU extension Ionela Voinescu
2020-02-12 15:36   ` Valentin Schneider
2020-02-11 18:45 ` [PATCH v3 5/7] cpufreq: add function to get the hardware max frequency Ionela Voinescu
2020-02-12  4:14   ` Viresh Kumar
2020-02-13 11:59   ` Valentin Schneider
2020-02-13 12:59     ` Ionela Voinescu
2020-02-13 15:22       ` Valentin Schneider
2020-02-11 18:45 ` [PATCH v3 6/7] arm64: use activity monitors for frequency invariance Ionela Voinescu
2020-02-12 18:59   ` Lukasz Luba
2020-02-13  9:47     ` Ionela Voinescu
2020-02-17 16:59   ` Valentin Schneider
2020-02-23 18:49     ` Ionela Voinescu
2020-02-11 18:45 ` [PATCH v3 7/7] clocksource/drivers/arm_arch_timer: validate arch_timer_rate Ionela Voinescu
2020-02-12  9:30   ` Valentin Schneider
2020-02-12 10:32     ` Ionela Voinescu
2020-02-12 10:01   ` Lukasz Luba
2020-02-12 10:12     ` Marc Zyngier
2020-02-12 10:54       ` Ionela Voinescu
2020-02-12 10:55       ` Lukasz Luba
2020-02-12 11:10         ` Marc Zyngier
2020-02-12 11:43           ` Lukasz Luba
2020-02-12 11:12         ` Valentin Schneider
2020-02-14  0:35   ` Thomas Gleixner
2020-02-14 15:45     ` Ionela Voinescu
2020-02-14 15:57       ` Ionela Voinescu

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