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From:   Song Liu <songliubraving@fb.com>
To:     David Ahern <dsahern@gmail.com>
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        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
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        "peterz@infradead.org" <peterz@infradead.org>,
        "acme@kernel.org" <acme@kernel.org>
Subject: Re: [RFC perf,bpf 5/5] perf util: generate bpf_prog_info_event for
 short living bpf programs
Thread-Topic: [RFC perf,bpf 5/5] perf util: generate bpf_prog_info_event for
 short living bpf programs
Thread-Index: AQHUdhL1KSxo541SK0a40CXb4K6c4qVDSleAgAAXYgA=
Date:   Tue, 6 Nov 2018 23:17:51 +0000
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> On Nov 6, 2018, at 1:54 PM, David Ahern <dsahern@gmail.com> wrote:
>=20
> On 11/6/18 1:52 PM, Song Liu wrote:
>> +
>> static int record__mmap_read_all(struct record *rec)
>> {
>> 	int err;
>>=20
>> +	err =3D record__mmap_process_vip_events(rec);
>> +	if (err)
>> +		return err;
>> +
>> 	err =3D record__mmap_read_evlist(rec, rec->evlist, false);
>> 	if (err)
>> 		return err;
>=20
> 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.

BPF prog load/unload events should be rare events in real world use cases.=
=20
So I think the overhead is OK. Also, I don't see an easy way to improve=20
this.=20

>=20
>> @@ -1686,6 +1734,8 @@ static struct option __record_options[] =3D {
>> 			  "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"),
>=20
> Why should this default on? If am recording FIB events, I don't care
> about BPF events.
>=20

I am OK with default off if that's the preferred way.=20

Thanks,
Song