linux-kernel - Re: [PATCH V6 07/14] perf/x86/intel: Generic support for hardware TopDown metrics

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Date:   Tue, 21 Jul 2020 11:43:27 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     kan.liang@...ux.intel.com
Cc:     acme@...hat.com, mingo@...nel.org, linux-kernel@...r.kernel.org,
        jolsa@...nel.org, eranian@...gle.com,
        alexander.shishkin@...ux.intel.com, ak@...ux.intel.com
Subject: Re: [PATCH V6 07/14] perf/x86/intel: Generic support for hardware
 TopDown metrics

On Fri, Jul 17, 2020 at 07:05:47AM -0700, kan.liang@...ux.intel.com wrote:
> @@ -1031,6 +1034,35 @@ int x86_schedule_events(struct cpu_hw_events *cpuc, int n, int *assign)
>  	return unsched ? -EINVAL : 0;
>  }
>  
> +static int add_nr_metric_event(struct cpu_hw_events *cpuc,
> +			       struct perf_event *event,
> +			       int *max_count, bool sibling)
> +{
> +	/* The TopDown metrics events cannot be shared. */
> +	if (is_metric_event(event) &&
> +	    (++cpuc->n_metric_event > INTEL_TD_METRIC_NUM)) {
> +		cpuc->n_metric_event--;
> +		return -EINVAL;
> +	}
> +
> +	/*
> +	 * Take the accepted metrics events into account for leader event.
> +	 */
> +	if (!sibling)
> +		*max_count += cpuc->n_metric_event;
> +	else if (is_metric_event(event))
> +		(*max_count)++;
> +
> +	return 0;
> +}
> +
> +static void del_nr_metric_event(struct cpu_hw_events *cpuc,
> +				struct perf_event *event)
> +{
> +	if (is_metric_event(event))
> +		cpuc->n_metric_event--;
> +}
> +
>  /*
>   * dogrp: true if must collect siblings events (group)
>   * returns total number of events and error code
> @@ -1066,6 +1098,10 @@ static int collect_events(struct cpu_hw_events *cpuc, struct perf_event *leader,
>  		cpuc->pebs_output = is_pebs_pt(leader) + 1;
>  	}
>  
> +	if (x86_pmu.intel_cap.perf_metrics &&
> +	    add_nr_metric_event(cpuc, leader, &max_count, false))
> +		return -EINVAL;
> +
>  	if (is_x86_event(leader)) {
>  		if (n >= max_count)
>  			return -EINVAL;
> @@ -1082,6 +1118,10 @@ static int collect_events(struct cpu_hw_events *cpuc, struct perf_event *leader,
>  		    event->state <= PERF_EVENT_STATE_OFF)
>  			continue;
>  
> +		if (x86_pmu.intel_cap.perf_metrics &&
> +		    add_nr_metric_event(cpuc, event, &max_count, true))
> +			return -EINVAL;
> +
>  		if (n >= max_count)
>  			return -EINVAL;
>  

Something like so perhaps ?

--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -1035,24 +1035,14 @@ int x86_schedule_events(struct cpu_hw_ev
 }
 
 static int add_nr_metric_event(struct cpu_hw_events *cpuc,
-			       struct perf_event *event,
-			       int *max_count, bool sibling)
+			       struct perf_event *event)
 {
-	/* The TopDown metrics events cannot be shared. */
-	if (is_metric_event(event) &&
-	    (++cpuc->n_metric_event > INTEL_TD_METRIC_NUM)) {
-		cpuc->n_metric_event--;
-		return -EINVAL;
+	if (is_metric_event(event)) {
+		if (cpuc->n_metric == INTEL_TD_METRIC_NUM)
+			return -EINVAL;
+		cpuc->n_metric++;
 	}
 
-	/*
-	 * Take the accepted metrics events into account for leader event.
-	 */
-	if (!sibling)
-		*max_count += cpuc->n_metric_event;
-	else if (is_metric_event(event))
-		(*max_count)++;
-
 	return 0;
 }
 
@@ -1060,7 +1050,24 @@ static void del_nr_metric_event(struct c
 				struct perf_event *event)
 {
 	if (is_metric_event(event))
-		cpuc->n_metric_event--;
+		cpuc->n_metric--;
+}
+
+static int collect_event(struct cpu_hw_events *cpuc, struct perf_event *event,
+			 int max_count, int n)
+{
+
+	if (x86_pmu.intel_cap.perf_metrics && add_nr_metric_event(cpuc, event))
+		return -EINVAL;
+
+	if (n >= max_count + cpuc->n_metric)
+		return -EINVAL;
+
+	cpuc->event_list[n] = event;
+	if (is_counter_pair(&event->hw))
+		cpuc->n_pair++;
+
+	return 0;
 }
 
 /*
@@ -1098,37 +1105,20 @@ static int collect_events(struct cpu_hw_
 		cpuc->pebs_output = is_pebs_pt(leader) + 1;
 	}
 
-	if (x86_pmu.intel_cap.perf_metrics &&
-	    add_nr_metric_event(cpuc, leader, &max_count, false))
+	if (is_x86_event(leader) && collect_event(cpuc, leader, max_count, n))
 		return -EINVAL;
+	n++;
 
-	if (is_x86_event(leader)) {
-		if (n >= max_count)
-			return -EINVAL;
-		cpuc->event_list[n] = leader;
-		n++;
-		if (is_counter_pair(&leader->hw))
-			cpuc->n_pair++;
-	}
 	if (!dogrp)
 		return n;
 
 	for_each_sibling_event(event, leader) {
-		if (!is_x86_event(event) ||
-		    event->state <= PERF_EVENT_STATE_OFF)
+		if (!is_x86_event(event) || event->state <= PERF_EVENT_STATE_OFF)
 			continue;
 
-		if (x86_pmu.intel_cap.perf_metrics &&
-		    add_nr_metric_event(cpuc, event, &max_count, true))
-			return -EINVAL;
-
-		if (n >= max_count)
+		if (collect_event(cpuc, event, max_count, n))
 			return -EINVAL;
-
-		cpuc->event_list[n] = event;
 		n++;
-		if (is_counter_pair(&event->hw))
-			cpuc->n_pair++;
 	}
 	return n;
 }
--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -313,7 +313,7 @@ struct cpu_hw_events {
 	 * Perf Metrics
 	 */
 	/* number of accepted metrics events */
-	int				n_metric_event;
+	int				n_metric;
 
 	/*
 	 * AMD specific bits