lkml.org 
[lkml]   [2016]   [Apr]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectLBR callchains from tracepoints
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 <eranian@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 <eranian@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1328826068-11713-10-git-send-email-eranian@google.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>

\
 
 \ /
  Last update: 2016-04-26 03:41    [W:0.061 / U:0.956 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site