RE: [PATCH 1/1] perf tools: perf diff for different binaries
From: Liang, Kan
Date: Wed Nov 05 2014 - 12:31:41 EST
> Hi Kan,
>
> On Tue, 4 Nov 2014 17:07:43 +0000, Kan Liang wrote:
> > Hi Namhyung,
> >
> >> > tchain_edit [.] f1
> >> > 0.14% 3.913444 tchain_edit [.] f2
> >> > 99.82% 1.005478 tchain_edit [.] f3
> >>
> >> Hmm.. I think it should be a default behavior for perf diff,
> >> otherwise -s symbol is almost meaningless IMHO.
> >
> > I think we need both instruction level and function level diff.
> > For debugging scaling issue, I think we need to do deeper analysis for
> > some cache or lock issue. The function level is too high granularity.
> >
> > The new option can be used to debug scaling regression issue.
> > If the binary/kernel is updated, it doesn't make sense to compare the
> > symbol address, since it should be changed. So comparing the function
> > should be more useful.
> >
> >
> >> What about setting the
> >> sort_sym.se_collapse in data_process() so that hists__match() can use
> >> symbol names?
> >
> > Yes, we can set it if we only do function level diff. But I'd like to
> > keep both. So I defined two sort keys.
> > "symbol" means "symbol address executed at the time of sample "
> > "symbol_name" means "name of function executed at the time of
> sample"
>
> Hmm.. I don't think the symbol sort key provides the instruction level diff
> that you want. If it finds a symbol it just use the start address of the
> symbol, not the exact address of the sample. Am I missing something?
>
No, the meaning of symbol in perf diff is different as in perf report. It uses
the exact address of the sample.
Here is current perf diff result and objdump fragment of the first binary.
You can see the exact address of the sample in function f3 was used, not the
start address.
33.55% [unknown] [.] 0x0000000000400554
48.13% [unknown] [.] 0x000000000040056b
[perf-test]#./perf diff -s dso,symbol --compute ratio ../../../v1_1_6perf.data
../../../v2_1_7perf.data
# Event 'cycles'
#
# Baseline Ratio Shared Object Symbol
# ........ .............. ................. .........................
#
[kernel.kallsyms] [k] __update_cpu_load
[kernel.kallsyms] [k] mod_timer
0.01% [kernel.kallsyms] [k] native_write_msr_safe
0.01% [kernel.kallsyms] [k] notifier_call_chain
0.01% [kernel.kallsyms] [k] perf_event_task_tick
[kernel.kallsyms] [k] rt_mutex_slowlock
0.01% [kernel.kallsyms] [k] run_posix_cpu_timers
0.01% [kernel.kallsyms] [k] run_timer_softirq
0.01% [kernel.kallsyms] [k] trigger_load_balance
0.01% [kernel.kallsyms] [k] update_vsyscall
[kernel.kallsyms] [k] wait_for_common
[kernel.kallsyms] [k] 0x000000000028482a
0.05% [unknown] [.] 0x0000000000400540
0.04% [unknown] [.] 0x0000000000400541
0.03% [unknown] [.] 0x000000000040054b
0.04% [unknown] [.] 0x0000000000400552
33.55% [unknown] [.] 0x0000000000400554
1.22% [unknown] [.] 0x000000000040055a
8.00% [unknown] [.] 0x000000000040055e
0.02% [unknown] [.] 0x0000000000400562
8.41% [unknown] [.] 0x0000000000400564
48.13% [unknown] [.] 0x000000000040056b
0.16% [unknown] [.] 0x0000000000400570
0.17% [unknown] [.] 0x0000000000400571
[unknown] [.] 0x0000000000400580
[unknown] [.] 0x0000000000400581
0.01% [unknown] [.] 0x0000000000400583
0.01% [unknown] [.] 0x0000000000400588
[unknown] [.] 0x000000000040058b
0.01% 1240.990221 [unknown] [.] 0x000000000040058d
[unknown] [.] 0x0000000000400590
0.06% [unknown] [.] 0x0000000000400591
[unknown] [.] 0x0000000000400593
0.04% [unknown] [.] 0x0000000000400595
0.01% 1240.603148 [unknown] [.] 0x0000000000400597
[unknown] [.] 0x000000000040059b
[unknown] [.] 0x000000000040059d
[unknown] [.] 0x00000000004005a1
[unknown] [.] 0x00000000004005a5
[unknown] [.] 0x00000000004005a7
[unknown] [.] 0x00000000004005a8
[unknown] [.] 0x00000000004005aa
[unknown] [.] 0x00000000004005ba
[unknown] [.] 0x00000000004005bf
[unknown] [.] 0x00000000004005c4
[unknown] [.] 0x00000000004005c9
[unknown] [.] 0x00000000004005ce
[unknown] [.] 0x00000000004005d2
[unknown] [.] 0x00000000004005d6
[unknown] [.] 0x00000000004005d8
[unknown] [.] 0x00000000004005f5
[perf-test]#objdump -d tchain_edit_1
0000000000400540 <f3>:
400540: 55 push %rbp
400541: 48 89 e5 mov %rsp,%rbp
400544: c7 45 f8 e8 03 00 00 movl $0x3e8,-0x8(%rbp)
40054b: c7 45 fc 00 00 00 00 movl $0x0,-0x4(%rbp)
400552: eb 14 jmp 400568 <f3+0x28>
400554: 8b 45 fc mov -0x4(%rbp),%eax
400557: 83 e0 01 and $0x1,%eax
40055a: 85 c0 test %eax,%eax
40055c: 74 06 je 400564 <f3+0x24>
40055e: 83 45 fc 01 addl $0x1,-0x4(%rbp)
400562: eb 04 jmp 400568 <f3+0x28>
400564: 83 45 fc 01 addl $0x1,-0x4(%rbp)
400568: 8b 45 fc mov -0x4(%rbp),%eax
40056b: 3b 45 f8 cmp -0x8(%rbp),%eax
40056e: 7c e4 jl 400554 <f3+0x14>
400570: 5d pop %rbp
400571: c3 retq
Thanks,
Kan
> Thanks,
> Namhyung
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