linux-kernel - Re: [PATCH 2/9] perf/x86/intel: Basic support for metrics counters

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Date:   Tue, 28 May 2019 14:15:08 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     kan.liang@...ux.intel.com
Cc:     acme@...nel.org, mingo@...hat.com, linux-kernel@...r.kernel.org,
        tglx@...utronix.de, jolsa@...nel.org, eranian@...gle.com,
        alexander.shishkin@...ux.intel.com, ak@...ux.intel.com
Subject: Re: [PATCH 2/9] perf/x86/intel: Basic support for metrics counters

On Tue, May 21, 2019 at 02:40:48PM -0700, kan.liang@...ux.intel.com wrote:
> +/*
> + * We model PERF_METRICS as more magic fixed-mode PMCs, one for each metric
> + * and another for the whole slots counter
> + *
> + * Internally they all map to Fixed Ctr 3 (SLOTS), and allocate PERF_METRICS
> + * as an extra_reg. PERF_METRICS has no own configuration, but we fill in
> + * the configuration of FxCtr3 to enforce that all the shared users of SLOTS
> + * have the same configuration.
> + */
> +#define INTEL_PMC_IDX_FIXED_METRIC_BASE		(INTEL_PMC_IDX_FIXED + 17)
> +#define INTEL_PMC_IDX_TD_RETIRING		(INTEL_PMC_IDX_FIXED_METRIC_BASE + 0)
> +#define INTEL_PMC_IDX_TD_BAD_SPEC		(INTEL_PMC_IDX_FIXED_METRIC_BASE + 1)
> +#define INTEL_PMC_IDX_TD_FE_BOUND		(INTEL_PMC_IDX_FIXED_METRIC_BASE + 2)
> +#define INTEL_PMC_IDX_TD_BE_BOUND		(INTEL_PMC_IDX_FIXED_METRIC_BASE + 3)
> +#define INTEL_PMC_MSK_ANY_SLOTS			((0xfull << INTEL_PMC_IDX_FIXED_METRIC_BASE) | \
> +						 INTEL_PMC_MSK_FIXED_SLOTS)
> +static inline bool is_metric_idx(int idx)
> +{
> +	return idx >= INTEL_PMC_IDX_FIXED_METRIC_BASE && idx <= INTEL_PMC_IDX_TD_BE_BOUND;
> +}

Something like:

	return (idx >> INTEL_PMC_IDX_FIXED_METRIC_BASE) & 0xf;

might be faster code... (if it wasn't for 64bit literals being a pain,
it could be a simple test instruction).