Messages in this thread | | | Date | Wed, 18 Nov 2015 12:13:08 +0800 | From | "Wangnan (F)" <> | Subject | Re: [PATCH 2/3] perf tools: Add callchain order support for libunwind DWARF unwinder |
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On 2015/11/17 23:05, Jiri Olsa wrote: > From: Jiri Olsa <jolsa@redhat.com> > > As reported by Milian, currently for DWARF unwind (both libdw > and libunwind) we display callchain in callee order only. > > Adding the support to follow callchain order setup to libunwind > DWARF unwinder, so we could get following output for report: > > $ perf record --call-graph dwarf ls > ... > $ perf report --no-children --stdio > > 39.26% ls libc-2.21.so [.] __strcoll_l > | > ---__strcoll_l > mpsort_with_tmp > mpsort_with_tmp > sort_files > main > __libc_start_main > _start > 0 > > $ perf report -g caller --no-children --stdio > ... > 39.26% ls libc-2.21.so [.] __strcoll_l > | > ---0 > _start > __libc_start_main > main > sort_files > mpsort_with_tmp > mpsort_with_tmp > __strcoll_l > > Reported-by: Milian Wolff <milian.wolff@kdab.com> > Based-on-patch-by: Milian Wolff <milian.wolff@kdab.com> > Link: http://lkml.kernel.org/n/tip-lmtbeqm403f3luw4jkjevsi5@git.kernel.org > Signed-off-by: Jiri Olsa <jolsa@kernel.org> > --- > tools/perf/util/unwind-libunwind.c | 47 ++++++++++++++++++++++++-------------- > 1 file changed, 30 insertions(+), 17 deletions(-) > > diff --git a/tools/perf/util/unwind-libunwind.c b/tools/perf/util/unwind-libunwind.c > index 0ae8844fe7a6..705e1c19f1ea 100644 > --- a/tools/perf/util/unwind-libunwind.c > +++ b/tools/perf/util/unwind-libunwind.c
[SNIP]
> > - unw_get_reg(&c, UNW_REG_IP, &ip); > - ret = ip ? entry(ip, ui->thread, cb, arg) : 0;
In original code if ip == 0 entry() won't be called.
> + if (callchain_param.order == ORDER_CALLER) > + j = max_stack - i - 1; > + ret = entry(ips[j], ui->thread, cb, arg);
But in new code event if ips[j] == 0 an entry will be built, which causes a behavior changes user noticable:
Before this patch:
# perf report --no-children --stdio --call-graph=callee ... 3.38% a.out a.out [.] funcc | ---funcc | --2.70%-- funcb funca main __libc_start_main _start
After this patch:
# perf report --no-children --stdio --call-graph=callee ... 3.38% a.out a.out [.] funcc | ---funcc | |--2.70%-- funcb | funca | main | __libc_start_main | _start | --0.68%-- 0
I'm not sure whether we can regard this behavior changing as a bugfix? I think there may be some reason the original code explicitly avoid creating an '0' entry.
Then I tried to find why perf can't get call frame on my case, and I guess there's something wrong whe dealing with 'call' command, because the instruction on it I can't get callchain from libunwind is a 'callq':
... 4005bf: be 00 00 00 00 mov $0x0,%esi 4005c4: 48 89 c7 mov %rax,%rdi 4005c7: e8 74 fe ff ff callq 400440 <gettimeofday@plt> us2 = tv2.tv_sec * 1000000 + tv2.tv_usec; 4005cc: 48 8b 04 24 mov (%rsp),%rax ...
But this is another problem, we can discuss it in a new thread.
Thank you.
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