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Date:   Wed, 5 Jul 2023 15:00:13 -0400
From:   Steven Rostedt <rostedt@goodmis.org>
To:     Valentin Schneider <vschneid@redhat.com>
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Subject: Re: [RFC PATCH 03/14] tracing/filters: Enable filtering a scalar
 field by a cpumask
Message-ID: <20230705150013.5ba7ddb8@gandalf.local.home>
In-Reply-To: <20230705181256.3539027-4-vschneid@redhat.com>
References: <20230705181256.3539027-1-vschneid@redhat.com>
        <20230705181256.3539027-4-vschneid@redhat.com>
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On Wed,  5 Jul 2023 19:12:45 +0100
Valentin Schneider <vschneid@redhat.com> wrote:

> +/* Optimisation of do_filter_cpumask() for scalar values */
> +static inline int
> +do_filter_cpumask_scalar(int op, unsigned int cpu, const struct cpumask *mask)
> +{
> +	switch (op) {
> +	case OP_EQ:
> +		return cpumask_equal(mask, cpumask_of(cpu));
> +	case OP_NE:
> +		return !cpumask_equal(mask, cpumask_of(cpu));

The above two can be optimized much more if the cpu is a scalar. If mask is
anything but a single CPU, then EQ will always be false, and NE will always
be true. If the mask contains a single CPU, then we should convert the mask
into the scalar CPU and just do:

	case OP_EQ:
		return mask_cpu == cpu;
	case op_NE:
		return maks_cpu != cpu;

-- Steve

> +	case OP_BAND:
> +		return cpumask_test_cpu(cpu, mask);
> +	default:
> +		return 0;
> +	}
> +}