netdev - Re: [PATCH v4 bpf-next 1/4] bpftool: introduce "prog profile" command

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Message-ID: <20200304203825.GC168640@krava>
Date:   Wed, 4 Mar 2020 21:38:25 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Song Liu <songliubraving@...com>
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org, quentin@...valent.com,
        kernel-team@...com, ast@...nel.org, daniel@...earbox.net,
        arnaldo.melo@...il.com, jolsa@...nel.org
Subject: Re: [PATCH v4 bpf-next 1/4] bpftool: introduce "prog profile" command

On Wed, Mar 04, 2020 at 10:07:07AM -0800, Song Liu wrote:

SNIP

> +
> +#include "profiler.skel.h"
> +
> +#define SAMPLE_PERIOD  0x7fffffffffffffffULL
> +struct profile_metric {
> +	const char *name;
> +	struct bpf_perf_event_value val;
> +	struct perf_event_attr attr;
> +	bool selected;
> +
> +	/* calculate ratios like instructions per cycle */
> +	const int ratio_metric; /* 0 for N/A, 1 for index 0 (cycles) */
> +	const char *ratio_desc;
> +	const float ratio_mul;
> +} metrics[] = {
> +	{
> +		.name = "cycles",
> +		.attr = {
> +			.sample_period = SAMPLE_PERIOD,

I don't think you need to set sample_period for counting.. why?

> +			.type = PERF_TYPE_HARDWARE,
> +			.config = PERF_COUNT_HW_CPU_CYCLES,

you could also add .exclude_user = 1

jirka