On 2015/11/18 16:48, Jiri Olsa wrote:
On Wed, Nov 18, 2015 at 03:20:36PM +0800, Wangnan (F) wrote: SNIPThen use perf to trace it: # ./pref record -g -F 9 --call-graph dwarf ./test_dwarf_unwind # ./perf report --no-children --stdio ... 1.23% test_dwarf_unwi test_dwarf_unwind [.] funcc | ---funcc | |--0.62%-- funcb | funca | main | __libc_start_main | _start | --0.62%-- 0 <-- I applied Jiri's patch in [1] so see this 0, which indicates a broken call chain.can't see this case after multiple running your test, just the 'end-of-the-callchain' zeros 49.14% test_dwarf_unwi [vdso] [.] __vdso_gettimeofday | ---__vdso_gettimeofday funcc funcb funca main __libc_start_main _start 0 40.78% test_dwarf_unwi [vdso] [.] 0x0000000000000987 | ---0x7ffe28ab7987 __vdso_gettimeofday funcc funcb funca main __libc_start_main _start 0 what kernel do you have?
My kernel is 4.3-rc4. Please see my reply to Ingo. It is possible a problem related to hardware and PEBS? Maybe on your system perf never capture samples on 'callq'? I tested 'cycle' and 'cycle:p', can't get such samples. Only 'cycles:pp' (the default event) have this problem. Thank you. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
