linux-kernel - Re: [RFC perf,bpf 5/5] perf util: generate bpf_prog_info

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Message-ID: <b984776a-ce69-ab16-ed87-1cea89c9d79a@gmail.com>
Date:   Tue, 6 Nov 2018 14:54:09 -0700
From:   David Ahern <dsahern@...il.com>
To:     Song Liu <songliubraving@...com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     kernel-team@...com, ast@...nel.org, daniel@...earbox.net,
        peterz@...radead.org, acme@...nel.org
Subject: Re: [RFC perf,bpf 5/5] perf util: generate bpf_prog_info_event for
 short living bpf programs

On 11/6/18 1:52 PM, Song Liu wrote:
> +
>  static int record__mmap_read_all(struct record *rec)
>  {
>  	int err;
>  
> +	err = record__mmap_process_vip_events(rec);
> +	if (err)
> +		return err;
> +
>  	err = record__mmap_read_evlist(rec, rec->evlist, false);
>  	if (err)
>  		return err;

Seems to me that is going to increase the overhead of perf on any system
doing BPF updates. The BPF events cause a wakeup every load and unload,
and perf processes not only the VIP events but then walks all of the
other maps.

> @@ -1686,6 +1734,8 @@ static struct option __record_options[] = {
>  			  "signal"),
>  	OPT_BOOLEAN(0, "dry-run", &dry_run,
>  		    "Parse options then exit"),
> +	OPT_BOOLEAN(0, "no-bpf-event", &record.no_bpf_event,
> +		    "do not record event on bpf program load/unload"),

Why should this default on? If am recording FIB events, I don't care
about BPF events.