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Message-ID: <6C5A9FBD-F50D-444C-9038-E9557EC850D2@fb.com>
Date: Tue, 6 Nov 2018 23:17:51 +0000
From: Song Liu <songliubraving@...com>
To: David Ahern <dsahern@...il.com>
CC: "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Kernel Team <Kernel-team@...com>,
"ast@...nel.org" <ast@...nel.org>,
"daniel@...earbox.net" <daniel@...earbox.net>,
"peterz@...radead.org" <peterz@...radead.org>,
"acme@...nel.org" <acme@...nel.org>
Subject: Re: [RFC perf,bpf 5/5] perf util: generate bpf_prog_info_event for
short living bpf programs
> On Nov 6, 2018, at 1:54 PM, David Ahern <dsahern@...il.com> wrote:
>
> 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.
BPF prog load/unload events should be rare events in real world use cases.
So I think the overhead is OK. Also, I don't see an easy way to improve
this.
>
>> @@ -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.
>
I am OK with default off if that's the preferred way.
Thanks,
Song
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