Em Tue, Apr 14, 2015 at 07:00:43PM +0530, sahil aggarwal escreveu:
> > This is incomplete: "multiple events for all CPUS" ok, but for a specific
> > thread? Or for all of them?
> If i have 2 CPU's, i made it run 2 threads each per CPU. Both threads
> have different streams for same tracepoints polling on them. Well, had
> to go with this approach since enabling tracepoints on all CPU when
> inherit was not working for me :(
My question stands: "Are you monitoring a specific thread? Or all
threads in the system"?
> > See this, look for the inherit flag, then look for the CPU arg to
> > sys_perf_event_open, many tracepoints, a process that creates a process that
> > creates a process that makes a networking call that hits net:*skb*
> > tracepoints,
> > is something like that that you want?
> This is exactly what i want. But things seem to be working in unexpected way.
Read below
> > [root@zoo ~]# perf stat -vv -e sched:* -e skb:* time time ping -c 1
> > 127.0.0.1
> > <SNIP>
> > ------------------------------------------------------------
> > perf_event_attr:
> > type 2
> > size 112
> > config 10b
> > { sample_period, sample_freq } 1
> > sample_type TIME|CPU|PERIOD|RAW
> > read_format TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING
> > disabled 1
> > inherit 1
> > enable_on_exec 1
> > exclude_guest 1
> > ------------------------------------------------------------
> > sys_perf_event_open: pid 9944 cpu -1 group_fd -1 flags 0x8
> > ------------------------------------------------------------
>
> I think i should figure out why mmap is failing when inherit=1, seeing
> this it doesn't make sense. Will get back to you if i find something.
'perf stat' doesn't use mmap, its just counting events, lemme try
mmaping that same workload:
[root@zoo ~]# trace -o /tmp/trace.output -vv --ev sched:* --ev skb:* time time
ping -c 1 127.0.0.1
<SNIP>
------------------------------------------------------------
perf_event_attr:
type 2
size 112
config 10b
{ sample_period, sample_freq } 1
sample_type IP|TID|TIME|ID|CPU|PERIOD|RAW
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 19784 cpu 0 group_fd -1 flags 0x8
sys_perf_event_open: pid 19784 cpu 1 group_fd -1 flags 0x8
sys_perf_event_open: pid 19784 cpu 2 group_fd -1 flags 0x8
sys_perf_event_open: pid 19784 cpu 3 group_fd -1 flags 0x8
------------------------------------------------------------
perf_event_attr:
type 2
size 112
config 10a
{ sample_period, sample_freq } 1
sample_type IP|TID|TIME|ID|CPU|PERIOD|RAW
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 19784 cpu 0 group_fd -1 flags 0x8
sys_perf_event_open: pid 19784 cpu 1 group_fd -1 flags 0x8
sys_perf_event_open: pid 19784 cpu 2 group_fd -1 flags 0x8
sys_perf_event_open: pid 19784 cpu 3 group_fd -1 flags 0x8
------------------------------------------------------------
perf_event_attr:
type 2
size 112
config 109
{ sample_period, sample_freq } 1
sample_type IP|TID|TIME|ID|CPU|PERIOD|RAW
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 19784 cpu 0 group_fd -1 flags 0x8
sys_perf_event_open: pid 19784 cpu 1 group_fd -1 flags 0x8
sys_perf_event_open: pid 19784 cpu 2 group_fd -1 flags 0x8
sys_perf_event_open: pid 19784 cpu 3 group_fd -1 flags 0x8
------------------------------------------------------------
<SNIP>
mmap size 528384B
perf event ring buffer mmapped per cpu
PING 127.0.0.1 (127.0.0.1) 56(84) bytes of data.
64 bytes from 127.0.0.1: icmp_seq=1 ttl=64 time=0.050 ms
--- 127.0.0.1 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.050/0.050/0.050/0.000 ms
0.00user 0.00system 0:00.00elapsed 50%CPU (0avgtext+0avgdata 2112maxresident)k
0inputs+0outputs (0major+100minor)pagefaults 0swaps
0.00user 0.00system 0:00.00elapsed 60%CPU (0avgtext+0avgdata 2112maxresident)k
0inputs+0outputs (0major+180minor)pagefaults 0swaps
[root@zoo ~]#
Ok, it works, but notice that it will create one file descriptor per event per
CPU (this machine has 4 CPUs), and then it will use an ioctl to ask the kernel
to send all events for an event on a CPU to the same ring buffer, so we end up
with just 4 ring buffers (perf mmaps), one per CPU:
>From tools/perf/util/evlist.c, function perf_evlist__mmap_per_evsel():
if (ioctl(fd, PERF_EVENT_IOC_SET_OUTPUT, *output) != 0)
That is why I asked you about what you are monitoring, that is not clear so
far, for me.
Above, we are not asking the kernel for cpu == -1 and thread == -1, that will
result in that -EINVAL, that is there for scalability reasons.
System wide is done by using CPU = N and thread = -1, with one mmap per CPU.
- Arnaldo
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