linux-kernel - Re: [Patch v8 06/12] perf/x86/intel/ds: Factor out PEBS record processing code to functions

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Message-ID: <20251022114917.GT3245006@noisy.programming.kicks-ass.net>
Date: Wed, 22 Oct 2025 13:49:17 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Dapeng Mi <dapeng1.mi@...ux.intel.com>
Cc: Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>, Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Andi Kleen <ak@...ux.intel.com>,
	Eranian Stephane <eranian@...gle.com>, linux-kernel@...r.kernel.org,
	linux-perf-users@...r.kernel.org, Dapeng Mi <dapeng1.mi@...el.com>,
	Kan Liang <kan.liang@...ux.intel.com>
Subject: Re: [Patch v8 06/12] perf/x86/intel/ds: Factor out PEBS record
 processing code to functions

On Wed, Oct 15, 2025 at 02:44:16PM +0800, Dapeng Mi wrote:
> Beside some PEBS record layout difference, arch-PEBS can share most of
> PEBS record processing code with adaptive PEBS. Thus, factor out these
> common processing code to independent inline functions, so they can be
> reused by subsequent arch-PEBS handler.
> 
> Suggested-by: Kan Liang <kan.liang@...ux.intel.com>
> Signed-off-by: Dapeng Mi <dapeng1.mi@...ux.intel.com>
> ---
>  arch/x86/events/intel/ds.c | 101 ++++++++++++++++++++++++-------------
>  1 file changed, 66 insertions(+), 35 deletions(-)
> 
> diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
> index a80881a20321..41acbf0a11c9 100644
> --- a/arch/x86/events/intel/ds.c
> +++ b/arch/x86/events/intel/ds.c
> @@ -2629,6 +2629,64 @@ static void intel_pmu_drain_pebs_nhm(struct pt_regs *iregs, struct perf_sample_d
>  	}
>  }
>  
> +static inline void __intel_pmu_handle_pebs_record(struct pt_regs *iregs,
> +						  struct pt_regs *regs,
> +						  struct perf_sample_data *data,
> +						  void *at, u64 pebs_status,
> +						  struct perf_event *events[],
> +						  short *counts, void **last,
> +						  setup_fn setup_sample)
> +{
> +	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
> +	struct perf_event *event;
> +	int bit;
> +
> +	for_each_set_bit(bit, (unsigned long *)&pebs_status, X86_PMC_IDX_MAX) {
> +		event = cpuc->events[bit];
> +
> +		if (WARN_ON_ONCE(!event) ||
> +		    WARN_ON_ONCE(!event->attr.precise_ip))
> +			continue;
> +
> +		if (counts[bit]++)
> +			__intel_pmu_pebs_event(event, iregs, regs, data,
> +					       last[bit], setup_sample);
> +
> +		last[bit] = at;
> +		/*
> +		 * perf_event_overflow() called by below __intel_pmu_pebs_last_event()
> +		 * could trigger interrupt throttle and clear all event pointers of
> +		 * the group in cpuc->events[] to NULL. So snapshot the event[] before
> +		 * it could be cleared. This avoids the possible NULL event pointer
> +		 * access and PEBS record loss.
> +		 */
> +		if (counts[bit] && !events[bit])
> +			events[bit] = cpuc->events[bit];
> +	}
> +}
> +
> +static inline void
> +__intel_pmu_handle_last_pebs_record(struct pt_regs *iregs, struct pt_regs *regs,
> +				    struct perf_sample_data *data, u64 mask,
> +				    struct perf_event *events[],
> +				    short *counts, void **last,
> +				    setup_fn setup_sample)
> +{
> +	struct perf_event *event;
> +	int bit;
> +
> +	for_each_set_bit(bit, (unsigned long *)&mask, X86_PMC_IDX_MAX) {
> +		if (!counts[bit])
> +			continue;
> +
> +		event = events[bit];
> +
> +		__intel_pmu_pebs_last_event(event, iregs, regs, data, last[bit],
> +					    counts[bit], setup_sample);
> +	}
> +
> +}

These need to be __always_inline, like the other functions that take
setup_fn. Otherwise the compiler might decide to not inline and then it
can't constant propagate this function and we get indirect calls.