Re: [RFC PATCH 03/14] tracing/filters: Enable filtering a scalar field by a cpumask

[Steven Rostedt]

On Wed,  5 Jul 2023 19:12:45 +0100
Valentin Schneider <vschneid@xxxxxxxxxx> 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;
> +	}
> +}