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SubjectRe: [RFC perf,bpf 5/5] perf util: generate bpf_prog_info_event for short living bpf programs
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> On Nov 6, 2018, at 1:54 PM, David Ahern <dsahern@gmail.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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