- Automagically create a 'bpf-output' event, easing the setup of BPF
C "scripts" that produce output via the perf ring buffer. Now it is
just a matter of calling any perf tool, such as 'trace', with a C
source file that references the __bpf_stdout__ output channel and
that channel will be created and connected to the script:
# trace -e nanosleep --event test_bpf_stdout.c usleep 1
0.013 ( 0.013 ms): usleep/2818 nanosleep(rqtp: 0x7ffcead45f40 ) ...
0.013 ( ): __bpf_stdout__:Raise a BPF event!..)
0.015 ( ): perf_bpf_probe:func_begin:(ffffffff81112460))
0.261 ( ): __bpf_stdout__:Raise a BPF event!..)
0.262 ( ): perf_bpf_probe:func_end:(ffffffff81112460 <- ffffffff81003d92))
0.264 ( 0.264 ms): usleep/2818 ... [continued]: nanosleep()) = 0
#
Further work is needed to reduce the number of lines in a perf bpf C source
file, this being the part where we greatly reduce the command line setup (Wang Nan)
- 'perf trace' now supports callchains, with 'trace --call-graph dwarf' using
libunwind, just like 'perf top', to ask the kernel for stack dumps for CFI
processing. This reduces the overhead by asking just for userspace callchains
and also only for the syscall exit tracepoint (raw_syscalls:sys_exit)
(Milian Wolff, Arnaldo Carvalho de Melo)
Try it with, for instance:
# perf trace --call dwarf ping 127.0.0.1
An excerpt of a system wide 'perf trace --call dwarf" session is at:
https://fedorapeople.org/~acme/perf/perf-trace--call-graph-dwarf--all-cpus.txt
You may need to bump the number of mmap pages, using -m/--mmap-pages,
but on a Broadwell machine the defaults allowed system wide tracing to
work without losing that many records, experiment with just some
syscalls, like:
# perf trace --call dwarf -e nanosleep,futex
All the targets available for 'perf record', 'perf top' (--pid, --tid, --cpu,
etc) should work. Also --duration may be interesting to try.
To get filenames from in various syscalls pointer args (open, ettc), add this
to the mix:
# perf probe 'vfs_getname=getname_flags:72 pathname=filename:string'
Making this work is next in line:
# trace --call dwarf --ev sched:sched_switch/call-graph=fp/ usleep 1
I.e. honouring per-tracepoint callchains in 'perf trace' in addition to
in raw_syscalls:sys_exit.
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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Merge tag 'perf-core-for-mingo-20160411' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux into perf/core
Pull perf/core improvements from Arnaldo Carvalho de Melo:
User visible changes:
- Automagically create a 'bpf-output' event, easing the setup of BPF
C "scripts" that produce output via the perf ring buffer. Now it is
just a matter of calling any perf tool, such as 'trace', with a C
source file that references the __bpf_stdout__ output channel and
that channel will be created and connected to the script:
# trace -e nanosleep --event test_bpf_stdout.c usleep 1
0.013 ( 0.013 ms): usleep/2818 nanosleep(rqtp: 0x7ffcead45f40 ) ...
0.013 ( ): __bpf_stdout__:Raise a BPF event!..)
0.015 ( ): perf_bpf_probe:func_begin:(ffffffff81112460))
0.261 ( ): __bpf_stdout__:Raise a BPF event!..)
0.262 ( ): perf_bpf_probe:func_end:(ffffffff81112460 <- ffffffff81003d92))
0.264 ( 0.264 ms): usleep/2818 ... [continued]: nanosleep()) = 0
#
Further work is needed to reduce the number of lines in a perf bpf C source
file, this being the part where we greatly reduce the command line setup (Wang Nan)
- 'perf trace' now supports callchains, with 'trace --call-graph dwarf' using
libunwind, just like 'perf top', to ask the kernel for stack dumps for CFI
processing. This reduces the overhead by asking just for userspace callchains
and also only for the syscall exit tracepoint (raw_syscalls:sys_exit)
(Milian Wolff, Arnaldo Carvalho de Melo)
Try it with, for instance:
# perf trace --call dwarf ping 127.0.0.1
An excerpt of a system wide 'perf trace --call dwarf" session is at:
https://fedorapeople.org/~acme/perf/perf-trace--call-graph-dwarf--all-cpus.txt
You may need to bump the number of mmap pages, using -m/--mmap-pages,
but on a Broadwell machine the defaults allowed system wide tracing to
work without losing that many records, experiment with just some
syscalls, like:
# perf trace --call dwarf -e nanosleep,futex
All the targets available for 'perf record', 'perf top' (--pid, --tid, --cpu,
etc) should work. Also --duration may be interesting to try.
To get filenames from in various syscalls pointer args (open, ettc), add this
to the mix:
# perf probe 'vfs_getname=getname_flags:72 pathname=filename:string'
Making this work is next in line:
# trace --call dwarf --ev sched:sched_switch/call-graph=fp/ usleep 1
I.e. honouring per-tracepoint callchains in 'perf trace' in addition to
in raw_syscalls:sys_exit.
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
bed9441ba7