Re: [PATCH perf,bpf 5/5] perf util: generate bpf_prog_info_event for short living bpf programs

On 11/21/18 2:35 PM, Song Liu wrote:

quoted

On Nov 21, 2018, at 2:11 PM, Alexei Starovoitov [off-list ref] wrote:

On Wed, Nov 21, 2018 at 11:55:02AM -0800, Song Liu wrote:

quoted

This patch enables perf-record to listen to bpf_event and generate
bpf_prog_info_event for bpf programs loaded and unloaded during
perf-record run.

To minimize latency between bpf_event and following bpf calls, separate
mmap with watermark of 1 is created to process these vip events. Then
a separate dummy event is attached to the special mmap. A separate thread
is used to only poll bpf events.

By default, perf-record will listen to bpf_event. Option no-bpf-event is
added in case the user would opt out.

I think only default perf-record for sampling should include it.
perf record -e for tracepoints, kprobes and anything else should imply no-bpf-event.

Maybe something like
   
    if (software_event && ! -g)
         no_bpf_event = true;

?

This will allow attaching kprobe on bpf helper and see which bpf program
calls it.

right. good point about -g (I assume you mean callgraph collection).
Indeed, if bpf progs unload before perf-report they won't be seen in
callgraphs too even for sw events, so we have to enable bpf_events
to see them.