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Message-ID: <CAM9d7chhpuKkUOet1YqvTsR4cc8WHrLTkofjA_meFY9-D_a7Mg@mail.gmail.com>
Date: Tue, 17 May 2022 16:14:49 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Chengdong Li <brytonlee01@...il.com>
Cc: Alexey Bayduraev <alexey.v.bayduraev@...ux.intel.com>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...nel.org>,
Riccardo Mancini <rickyman7@...il.com>,
Adrian Hunter <adrian.hunter@...el.com>,
Ian Rogers <irogers@...gle.com>,
German Gomez <german.gomez@....com>,
linux-perf-users <linux-perf-users@...r.kernel.org>,
linux-kernel <linux-kernel@...r.kernel.org>,
Andi Kleen <ak@...ux.intel.com>, likexu@...cent.com,
chengdongli@...cent.com
Subject: Re: [RESEND PATCH v2] perf tools: fix callstack entries and nr print message
Hello,
On Mon, May 16, 2022 at 6:57 PM Chengdong Li <brytonlee01@...il.com> wrote:
>
> From: Chengdong Li <chengdongli@...cent.com>
>
> when generating callstack information from branch_stack(Intel LBR),
> the actual number of callstack entry should be bigger than the number
> of branch_stack, for example:
>
> branch_stack records:
> B() -> C()
> A() -> B()
> converted callstack records should be:
> C()
> B()
> A()
> though, the number of callstack equals
> to the number of branch stack plus 1.
>
> This patch fixes above issue in branch_stack__printf(). For example,
>
> # echo 'scale=2000; 4*a(1)' > cmd
> # perf record --call-graph lbr bc -l < cmd
>
> Before applying this patch, `perf script -D` output:
>
> 1220022677386876 0x2a40 [0xd8]: PERF_RECORD_SAMPLE(IP, 0x4002): 17990/17990: 0x40a6d6 period: 894172 addr: 0
> ... LBR call chain: nr:8
> ..... 0: fffffffffffffe00
> ..... 1: 000000000040a410
> ..... 2: 000000000040573c
> ..... 3: 0000000000408650
> ..... 4: 00000000004022f2
> ..... 5: 00000000004015f5
> ..... 6: 00007f5ed6dcb553
> ..... 7: 0000000000401698
> ... FP chain: nr:2
> ..... 0: fffffffffffffe00
> ..... 1: 000000000040a6d8
> ... branch callstack: nr:6 # which is not consistent with LBR records.
> ..... 0: 000000000040a410
> ..... 1: 0000000000408650 # ditto
> ..... 2: 00000000004022f2
> ..... 3: 00000000004015f5
> ..... 4: 00007f5ed6dcb553
> ..... 5: 0000000000401698
> ... thread: bc:17990
> ...... dso: /usr/bin/bc
> bc 17990 1220022.677386: 894172 cycles:
> 40a410 [unknown] (/usr/bin/bc)
> 40573c [unknown] (/usr/bin/bc)
> 408650 [unknown] (/usr/bin/bc)
> 4022f2 [unknown] (/usr/bin/bc)
> 4015f5 [unknown] (/usr/bin/bc)
> 7f5ed6dcb553 __libc_start_main+0xf3 (/usr/lib64/libc-2.17.so)
> 401698 [unknown] (/usr/bin/bc)
>
> After applied:
>
> 1220022677386876 0x2a40 [0xd8]: PERF_RECORD_SAMPLE(IP, 0x4002): 17990/17990: 0x40a6d6 period: 894172 addr: 0
> ... LBR call chain: nr:8
> ..... 0: fffffffffffffe00
> ..... 1: 000000000040a410
> ..... 2: 000000000040573c
> ..... 3: 0000000000408650
> ..... 4: 00000000004022f2
> ..... 5: 00000000004015f5
> ..... 6: 00007f5ed6dcb553
> ..... 7: 0000000000401698
> ... FP chain: nr:2
> ..... 0: fffffffffffffe00
> ..... 1: 000000000040a6d8
> ... branch callstack: nr:7
> ..... 0: 000000000040a410
> ..... 1: 000000000040573c
> ..... 2: 0000000000408650
> ..... 3: 00000000004022f2
> ..... 4: 00000000004015f5
> ..... 5: 00007f5ed6dcb553
> ..... 6: 0000000000401698
> ... thread: bc:17990
> ...... dso: /usr/bin/bc
> bc 17990 1220022.677386: 894172 cycles:
> 40a410 [unknown] (/usr/bin/bc)
> 40573c [unknown] (/usr/bin/bc)
> 408650 [unknown] (/usr/bin/bc)
> 4022f2 [unknown] (/usr/bin/bc)
> 4015f5 [unknown] (/usr/bin/bc)
> 7f5ed6dcb553 __libc_start_main+0xf3 (/usr/lib64/libc-2.17.so)
> 401698 [unknown] (/usr/bin/bc)
>
> Change from v1:
> - refined code style according to Jiri's review comments.
>
> Signed-off-by: Chengdong Li <chengdongli@...cent.com>
Acked-by: Namhyung Kim <namhyung@...nel.org>
Thanks,
Namhyung
> ---
> tools/perf/util/session.c | 26 +++++++++++++++++++++-----
> 1 file changed, 21 insertions(+), 5 deletions(-)
>
> diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
> index f9a320694b85..a7f93f5a1ac8 100644
> --- a/tools/perf/util/session.c
> +++ b/tools/perf/util/session.c
> @@ -1151,9 +1151,20 @@ static void branch_stack__printf(struct perf_sample *sample, bool callstack)
> struct branch_entry *entries = perf_sample__branch_entries(sample);
> uint64_t i;
>
> - printf("%s: nr:%" PRIu64 "\n",
> - !callstack ? "... branch stack" : "... branch callstack",
> - sample->branch_stack->nr);
> + if (!callstack) {
> + printf("%s: nr:%" PRIu64 "\n", "... branch stack", sample->branch_stack->nr);
> + } else {
> + /* the reason of adding 1 to nr is because after expanding
> + * branch stack it generates nr + 1 callstack records. e.g.,
> + * B()->C()
> + * A()->B()
> + * the final callstack should be:
> + * C()
> + * B()
> + * A()
> + */
> + printf("%s: nr:%" PRIu64 "\n", "... branch callstack", sample->branch_stack->nr+1);
> + }
>
> for (i = 0; i < sample->branch_stack->nr; i++) {
> struct branch_entry *e = &entries[i];
> @@ -1169,8 +1180,13 @@ static void branch_stack__printf(struct perf_sample *sample, bool callstack)
> (unsigned)e->flags.reserved,
> e->flags.type ? branch_type_name(e->flags.type) : "");
> } else {
> - printf("..... %2"PRIu64": %016" PRIx64 "\n",
> - i, i > 0 ? e->from : e->to);
> + if (i == 0) {
> + printf("..... %2"PRIu64": %016" PRIx64 "\n"
> + "..... %2"PRIu64": %016" PRIx64 "\n",
> + i, e->to, i+1, e->from);
> + } else {
> + printf("..... %2"PRIu64": %016" PRIx64 "\n", i+1, e->from);
> + }
> }
> }
> }
> --
> 2.27.0
>
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