2016-03-31 18:08:13

by Arnaldo Carvalho de Melo

Subject: perf trace + BPF

Hi Wang,

Trying to get back at working with 'perf trace' + BPF and I'm
noticing that the perf_event_attr->sample_type for the BPF events are
different than the ones for the raw_syscalls:sys_{enter,exit} or to
other tracepoint events we may ask 'perf trace' to set up, for instance,
for:

perf trace -vv -T --ev sched:sched_switch --ev bpf-output/no-inherit,name=evt/ --ev /home/acme/bpf/test_bpf_trace.c/map:channel.event=evt/ usleep 10

We get these sample types (full perf_event_attr dump at the end of this
message):

sched:sched_switch:
sample_type IP|TID|TIME|CPU|PERIOD|RAW|IDENTIFIER

[root@jouet ~]# perf probe -l
perf_bpf_probe:func_begin (on SyS_nanosleep@linux/kernel/time/hrtimer.c)
perf_bpf_probe:func_end (on SyS_nanosleep%return@linux/kernel/time/hrtimer.c)

sample_type IP|TID|RAW|IDENTIFIER

raw_syscalls:sys_{enter,exit}:

sample_type IP|TID|TIME|CPU|PERIOD|RAW|IDENTIFIER

I guess this is an interaction with that "no-inherit" part, probably we need to
set PERF_SAMPLE_TIME by some other means...

- Arnaldo


------------------------------------------------------------
perf_event_attr:
type 2
size 112
config 0x110
{ sample_period, sample_freq } 1
sample_type IP|TID|TIME|CPU|PERIOD|RAW|IDENTIFIER
read_format ID
disabled 1
inherit 1
mmap 1
comm 1
enable_on_exec 1
task 1
sample_id_all 1
exclude_guest 1
mmap2 1
comm_exec 1
{ wakeup_events, wakeup_watermark } 1
------------------------------------------------------------
sys_perf_event_open: pid 32425 cpu 0 group_fd -1 flags 0x8
sys_perf_event_open: pid 32425 cpu 1 group_fd -1 flags 0x8
sys_perf_event_open: pid 32425 cpu 2 group_fd -1 flags 0x8
sys_perf_event_open: pid 32425 cpu 3 group_fd -1 flags 0x8
------------------------------------------------------------
perf_event_attr:
type 1
size 112
config 0xa
{ sample_period, sample_freq } 1
sample_type IP|TID|RAW|IDENTIFIER
read_format ID
disabled 1
enable_on_exec 1
sample_id_all 1
exclude_guest 1
{ wakeup_events, wakeup_watermark } 1
------------------------------------------------------------
sys_perf_event_open: pid 32425 cpu 0 group_fd -1 flags 0x8
sys_perf_event_open: pid 32425 cpu 1 group_fd -1 flags 0x8
sys_perf_event_open: pid 32425 cpu 2 group_fd -1 flags 0x8
sys_perf_event_open: pid 32425 cpu 3 group_fd -1 flags 0x8
------------------------------------------------------------
perf_event_attr:
type 2
size 112
config 0x7c5
{ sample_period, sample_freq } 1
sample_type IP|TID|TIME|CPU|PERIOD|RAW|IDENTIFIER
read_format ID
disabled 1
inherit 1
enable_on_exec 1
sample_id_all 1
exclude_guest 1
{ wakeup_events, wakeup_watermark } 1
------------------------------------------------------------
sys_perf_event_open: pid 32425 cpu 0 group_fd -1 flags 0x8
sys_perf_event_open: pid 32425 cpu 1 group_fd -1 flags 0x8
sys_perf_event_open: pid 32425 cpu 2 group_fd -1 flags 0x8
sys_perf_event_open: pid 32425 cpu 3 group_fd -1 flags 0x8
------------------------------------------------------------
perf_event_attr:
type 2
size 112
config 0x7c4
{ sample_period, sample_freq } 1
sample_type IP|TID|TIME|CPU|PERIOD|RAW|IDENTIFIER
read_format ID
disabled 1
inherit 1
enable_on_exec 1
sample_id_all 1
exclude_guest 1
{ wakeup_events, wakeup_watermark } 1
------------------------------------------------------------
sys_perf_event_open: pid 32425 cpu 0 group_fd -1 flags 0x8
sys_perf_event_open: pid 32425 cpu 1 group_fd -1 flags 0x8
sys_perf_event_open: pid 32425 cpu 2 group_fd -1 flags 0x8
sys_perf_event_open: pid 32425 cpu 3 group_fd -1 flags 0x8
------------------------------------------------------------
perf_event_attr:
type 2
size 112
config 0x11
{ sample_period, sample_freq } 1
sample_type IP|TID|TIME|CPU|PERIOD|RAW|IDENTIFIER
read_format ID
disabled 1
inherit 1
enable_on_exec 1
sample_id_all 1
exclude_guest 1
{ wakeup_events, wakeup_watermark } 1
------------------------------------------------------------
sys_perf_event_open: pid 32425 cpu 0 group_fd -1 flags 0x8
sys_perf_event_open: pid 32425 cpu 1 group_fd -1 flags 0x8
sys_perf_event_open: pid 32425 cpu 2 group_fd -1 flags 0x8
sys_perf_event_open: pid 32425 cpu 3 group_fd -1 flags 0x8
------------------------------------------------------------
perf_event_attr:
type 2
size 112
config 0x10
{ sample_period, sample_freq } 1
sample_type IP|TID|TIME|CPU|PERIOD|RAW|IDENTIFIER
read_format ID
disabled 1
inherit 1
enable_on_exec 1
sample_id_all 1
exclude_guest 1
{ wakeup_events, wakeup_watermark } 1
------------------------------------------------------------
sys_perf_event_open: pid 32425 cpu 0 group_fd -1 flags 0x8
sys_perf_event_open: pid 32425 cpu 1 group_fd -1 flags 0x8
sys_perf_event_open: pid 32425 cpu 2 group_fd -1 flags 0x8
sys_perf_event_open: pid 32425 cpu 3 group_fd -1 flags 0x8
mmap size 528384B

2016-04-01 13:30:20

by Wang Nan

Subject: Re: perf trace + BPF

On 2016/4/1 2:08, Arnaldo Carvalho de Melo wrote:
> Hi Wang,
>
> Trying to get back at working with 'perf trace' + BPF and I'm
> noticing that the perf_event_attr->sample_type for the BPF events are
> different than the ones for the raw_syscalls:sys_{enter,exit} or to
> other tracepoint events we may ask 'perf trace' to set up, for instance,
> for:
>
> perf trace -vv -T --ev sched:sched_switch --ev bpf-output/no-inherit,name=evt/ --ev /home/acme/bpf/test_bpf_trace.c/map:channel.event=evt/ usleep 10
>
> We get these sample types (full perf_event_attr dump at the end of this
> message):
>
> sched:sched_switch:
> sample_type IP|TID|TIME|CPU|PERIOD|RAW|IDENTIFIER
>
> [root@jouet ~]# perf probe -l
> perf_bpf_probe:func_begin (on SyS_nanosleep@linux/kernel/time/hrtimer.c)
> perf_bpf_probe:func_end (on SyS_nanosleep%return@linux/kernel/time/hrtimer.c)
>
> sample_type IP|TID|RAW|IDENTIFIER
>
> raw_syscalls:sys_{enter,exit}:
>
> sample_type IP|TID|TIME|CPU|PERIOD|RAW|IDENTIFIER
>
> I guess this is an interaction with that "no-inherit" part, probably we need to
> set PERF_SAMPLE_TIME by some other means...

Please see [1]. Not related to no-inherit, just because the bpf-output event
is not a tracepoint.

And glad to see you restart working on my patches again!

Thank you.

[1]
http://lkml.kernel.org/g/[email protected]



> - Arnaldo
>

2016-04-01 13:50:46

by Arnaldo Carvalho de Melo

Subject: Re: perf trace + BPF

Em Fri, Apr 01, 2016 at 09:29:52PM +0800, Wangnan (F) escreveu:
>
>
> On 2016/4/1 2:08, Arnaldo Carvalho de Melo wrote:
> >Hi Wang,
> >
> > Trying to get back at working with 'perf trace' + BPF and I'm
> >noticing that the perf_event_attr->sample_type for the BPF events are
> >different than the ones for the raw_syscalls:sys_{enter,exit} or to
> >other tracepoint events we may ask 'perf trace' to set up, for instance,
> >for:
> >
> >perf trace -vv -T --ev sched:sched_switch --ev bpf-output/no-inherit,name=evt/ --ev /home/acme/bpf/test_bpf_trace.c/map:channel.event=evt/ usleep 10
> >
> >We get these sample types (full perf_event_attr dump at the end of this
> >message):
> >
> >sched:sched_switch:
> >sample_type IP|TID|TIME|CPU|PERIOD|RAW|IDENTIFIER
> >
> >[root@jouet ~]# perf probe -l
> > perf_bpf_probe:func_begin (on SyS_nanosleep@linux/kernel/time/hrtimer.c)
> > perf_bpf_probe:func_end (on SyS_nanosleep%return@linux/kernel/time/hrtimer.c)
> >
> > sample_type IP|TID|RAW|IDENTIFIER
> >
> >raw_syscalls:sys_{enter,exit}:
> >
> > sample_type IP|TID|TIME|CPU|PERIOD|RAW|IDENTIFIER
> >
> >I guess this is an interaction with that "no-inherit" part, probably we need to
> >set PERF_SAMPLE_TIME by some other means...
>
> Please see [1]. Not related to no-inherit, just because the bpf-output event
> is not a tracepoint.

Right, that was a dead end of mine when investigating this, thanks for
fixing this up!

> And glad to see you restart working on my patches again!

Yeah, hopefully this time we'll get most of what is outstanding merged.

I want to at some time experiment with doing things 'perf trace' needs
with BPF, behind the scenes :-)

> Thank you.
>
> [1] http://lkml.kernel.org/g/[email protected]
>
>
>
> >- Arnaldo
> >
>