Em Mon, Apr 25, 2016 at 10:03:58PM -0300, Arnaldo Carvalho de Melo escreveu:
> I now need to continue investigation why this doesn't seem to work from
> tracepoints...
Bummer, the changeset (at the end of this message) hasn't any
explanation, is this really impossible? I.e. LBR callstacks from
tracepoints? Even if we set perf_event_attr.exclude_callchain_kernel?
I've read somewhere that LBR wouldn't work for the kernel, but when I
tried, for cycles:ppp I got:
[acme@jouet linux]$ perf record --call-graph lbr usleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.018 MB perf.data (9 samples) ]
[acme@jouet linux]$ perf evlist -v
cycles:ppp: size: 112, { sample_period, sample_freq }: 4000,
sample_type: IP|TID|TIME|CALLCHAIN|PERIOD|BRANCH_STACK, disabled: 1,
inherit: 1, mmap: 1, comm: 1, freq: 1, enable_on_exec: 1, task: 1,
precise_ip: 3, sample_id_all: 1, exclude_guest: 1, mmap2: 1, comm_exec:
1, branch_sample_type: USER|CALL_STACK|NO_FLAGS|NO_CYCLES
[acme@jouet linux]$
- 59.69% usleep [kernel] [k] vma_interval_tree_insert
→vma_interval_tree_insert [kernel]
vma_adjust [kernel]
__split_vma.isra.31 [kernel]
split_vma [kernel]
mprotect_fixup [kernel]
sys_mprotect [kernel]
entry_SYSCALL_64_fastpath [kernel]
mprotect ld-2.22.so
_dl_relocate_object ld-2.22.so
memcpy@GLIBC_2.2.5 libc-2.22.so
_dl_relocate_object ld-2.22.so
__gettimeofday libc-2.22.so
_dl_vdso_vsym libc-2.22.so
_dl_lookup_symbol_x ld-2.22.so
This was done on a Broadwell system (ThinkPad t450s).
- Arnaldo
commit 2481c5fa6db0237e4f0168f88913178b2b495b7c
Author: Stephane Eranian <eran...@google.com>
Date: Thu Feb 9 23:20:59 2012 +0100
perf: Disable PERF_SAMPLE_BRANCH_* when not supported
PERF_SAMPLE_BRANCH_* is disabled for:
- SW events (sw counters, tracepoints)
- HW breakpoints
- ALL but Intel x86 architecture
- AMD64 processors
Signed-off-by: Stephane Eranian <eran...@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijls...@chello.nl>
Link:
http://lkml.kernel.org/r/1328826068-11713-10-git-send-email-eran...@google.com
Signed-off-by: Ingo Molnar <mi...@elte.hu>
