linux-kernel - Re: [PATCH V2 04/23] perf/x86/intel: Support adaptive PEBSv4

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Message-ID: <20190321211710.GC7905@worktop.programming.kicks-ass.net>
Date:   Thu, 21 Mar 2019 22:17:10 +0100
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 V2 04/23] perf/x86/intel: Support adaptive PEBSv4

On Thu, Mar 21, 2019 at 01:56:44PM -0700, kan.liang@...ux.intel.com wrote:
> +static inline void *next_pebs_record(void *p)
> +{
> +	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
> +	unsigned int size;
> +
> +	if (x86_pmu.intel_cap.pebs_format < 4)
> +		size = x86_pmu.pebs_record_size;
> +	else
> +		size = cpuc->pebs_record_size;
> +	return p + size;
> +}

> @@ -1323,19 +1580,19 @@ get_next_pebs_record_by_bit(void *base, void *top, int bit)
>  	if (base == NULL)
>  		return NULL;
>  
> -	for (at = base; at < top; at += x86_pmu.pebs_record_size) {
> -		struct pebs_record_nhm *p = at;
> +	for (at = base; at < top; at = next_pebs_record(at)) {
> +		unsigned long status = get_pebs_status(at);

afaict we do not mix base and adaptive records, and thus the above
really could use cpuc->pebs_record_size unconditionally, right?