From: Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>
To: kan.liang@linux.intel.com
Cc: jolsa@redhat.com, peterz@infradead.org, mingo@redhat.com,
linux-kernel@vger.kernel.org, namhyung@kernel.org,
adrian.hunter@intel.com, mathieu.poirier@linaro.org,
ravi.bangoria@linux.ibm.com, alexey.budankov@linux.intel.com,
vitaly.slobodskoy@intel.com, pavel.gerasimov@intel.com,
mpe@ellerman.id.au, eranian@google.com, ak@linux.intel.com
Subject: Re: [PATCH 02/12] perf tools: Support PERF_SAMPLE_BRANCH_HW_INDEX
Date: Thu, 5 Mar 2020 17:25:09 -0300 [thread overview]
Message-ID: <20200305202509.GA17483@kernel.org> (raw)
In-Reply-To: <20200228163011.19358-3-kan.liang@linux.intel.com>
Em Fri, Feb 28, 2020 at 08:30:01AM -0800, kan.liang@linux.intel.com escreveu:
> From: Kan Liang <kan.liang@linux.intel.com>
>
> A new branch sample type PERF_SAMPLE_BRANCH_HW_INDEX has been introduced
> in latest kernel.
>
> Enable HW_INDEX by default in LBR call stack mode.
> If kernel doesn't support the sample type, switching it off.
>
> Add HW_INDEX in attr_fprintf as well. User can check whether the branch
> sample type is set via debug information or header.
So while this works with a kernel where PERF_SAMPLE_BRANCH_HW_INDEX is
present and we get, from the committer notes I was putting together
while testing/applying this cset:
First collect some samples with LBR callchains, system wide, for a few
seconds:
# perf record --call-graph lbr -a sleep 5
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.625 MB perf.data (224 samples) ]
#
Now lets use 'perf evlist -v' to look at the branch_sample_type:
# perf evlist -v
cycles: size: 120, { sample_period, sample_freq }: 4000, sample_type: IP|TID|TIME|CALLCHAIN|CPU|PERIOD|BRANCH_STACK, read_format: ID, disabled: 1, inherit: 1, mmap: 1, comm: 1, freq: 1, task: 1, precise_ip: 3, sample_id_all: 1, exclude_guest: 1, mmap2: 1, comm_exec: 1, ksymbol: 1, bpf_event: 1, branch_sample_type: USER|CALL_STACK|NO_FLAGS|NO_CYCLES|HW_INDEX
#
So the machine has the kernel feature, and it was correctly added to
perf_event_attr.branch_sample_type, for the default 'cycles' event.
Cool, and look at that 'attr.precise_ip: 3' part, the kernel is OK with
having that together with attr.branch_sample_type with HW_INDEX set.
The problem happens when I go test this in an older kernel, where the
kernel doesn't know about HW_INDEX, we get it disabled but then
precise_ip is set to zero in its detection , even if at the end we get
it to 3, as expected, which got me a bit confused, I'll investigate this
a bit more to try and avoid these extra probes for the max precise level
that fails in older kernels due to branch_sample_type having HW_INDEX
:-\
# perf record -vv --call-graph lbr -a sleep 5
<SNIP>
------------------------------------------------------------
perf_event_attr:
size 120
{ sample_period, sample_freq } 4000
sample_type IP|TID|TIME|CALLCHAIN|CPU|PERIOD|BRANCH_STACK
read_format ID
disabled 1
inherit 1
mmap 1
comm 1
freq 1
task 1
precise_ip 3
sample_id_all 1
exclude_guest 1
mmap2 1
comm_exec 1
ksymbol 1
bpf_event 1
branch_sample_type USER|CALL_STACK|NO_FLAGS|NO_CYCLES|HW_INDEX
------------------------------------------------------------
sys_perf_event_open: pid -1 cpu 0 group_fd -1 flags 0x8
sys_perf_event_open failed, error -95
decreasing precise_ip by one (2)
------------------------------------------------------------
perf_event_attr:
size 120
{ sample_period, sample_freq } 4000
sample_type IP|TID|TIME|CALLCHAIN|CPU|PERIOD|BRANCH_STACK
read_format ID
disabled 1
inherit 1
mmap 1
comm 1
freq 1
task 1
precise_ip 2
sample_id_all 1
exclude_guest 1
mmap2 1
comm_exec 1
ksymbol 1
bpf_event 1
branch_sample_type USER|CALL_STACK|NO_FLAGS|NO_CYCLES|HW_INDEX
------------------------------------------------------------
sys_perf_event_open: pid -1 cpu 0 group_fd -1 flags 0x8
sys_perf_event_open failed, error -95
decreasing precise_ip by one (1)
------------------------------------------------------------
perf_event_attr:
size 120
{ sample_period, sample_freq } 4000
sample_type IP|TID|TIME|CALLCHAIN|CPU|PERIOD|BRANCH_STACK
read_format ID
disabled 1
inherit 1
mmap 1
comm 1
freq 1
task 1
precise_ip 1
sample_id_all 1
exclude_guest 1
mmap2 1
comm_exec 1
ksymbol 1
bpf_event 1
branch_sample_type USER|CALL_STACK|NO_FLAGS|NO_CYCLES|HW_INDEX
------------------------------------------------------------
sys_perf_event_open: pid -1 cpu 0 group_fd -1 flags 0x8
sys_perf_event_open failed, error -95
decreasing precise_ip by one (0)
------------------------------------------------------------
perf_event_attr:
size 120
{ sample_period, sample_freq } 4000
sample_type IP|TID|TIME|CALLCHAIN|CPU|PERIOD|BRANCH_STACK
read_format ID
disabled 1
inherit 1
mmap 1
comm 1
freq 1
task 1
sample_id_all 1
exclude_guest 1
mmap2 1
comm_exec 1
ksymbol 1
bpf_event 1
branch_sample_type USER|CALL_STACK|NO_FLAGS|NO_CYCLES|HW_INDEX
------------------------------------------------------------
sys_perf_event_open: pid -1 cpu 0 group_fd -1 flags 0x8
sys_perf_event_open failed, error -22
switching off branch HW index support
------------------------------------------------------------
perf_event_attr:
size 120
{ sample_period, sample_freq } 4000
sample_type IP|TID|TIME|CALLCHAIN|CPU|PERIOD|BRANCH_STACK
read_format ID
disabled 1
inherit 1
mmap 1
comm 1
freq 1
task 1
precise_ip 3
sample_id_all 1
exclude_guest 1
mmap2 1
comm_exec 1
ksymbol 1
bpf_event 1
branch_sample_type USER|CALL_STACK|NO_FLAGS|NO_CYCLES
------------------------------------------------------------
> Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
> ---
> tools/perf/util/evsel.c | 15 ++++++++++++---
> tools/perf/util/evsel.h | 1 +
> tools/perf/util/perf_event_attr_fprintf.c | 1 +
> 3 files changed, 14 insertions(+), 3 deletions(-)
>
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index 05883a45de5b..816d930d774e 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -712,7 +712,8 @@ static void __perf_evsel__config_callchain(struct evsel *evsel,
> attr->branch_sample_type = PERF_SAMPLE_BRANCH_USER |
> PERF_SAMPLE_BRANCH_CALL_STACK |
> PERF_SAMPLE_BRANCH_NO_CYCLES |
> - PERF_SAMPLE_BRANCH_NO_FLAGS;
> + PERF_SAMPLE_BRANCH_NO_FLAGS |
> + PERF_SAMPLE_BRANCH_HW_INDEX;
> }
> } else
> pr_warning("Cannot use LBR callstack with branch stack. "
> @@ -763,7 +764,8 @@ perf_evsel__reset_callgraph(struct evsel *evsel,
> if (param->record_mode == CALLCHAIN_LBR) {
> perf_evsel__reset_sample_bit(evsel, BRANCH_STACK);
> attr->branch_sample_type &= ~(PERF_SAMPLE_BRANCH_USER |
> - PERF_SAMPLE_BRANCH_CALL_STACK);
> + PERF_SAMPLE_BRANCH_CALL_STACK |
> + PERF_SAMPLE_BRANCH_HW_INDEX);
> }
> if (param->record_mode == CALLCHAIN_DWARF) {
> perf_evsel__reset_sample_bit(evsel, REGS_USER);
> @@ -1673,6 +1675,8 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
> evsel->core.attr.ksymbol = 0;
> if (perf_missing_features.bpf)
> evsel->core.attr.bpf_event = 0;
> + if (perf_missing_features.branch_hw_idx)
> + evsel->core.attr.branch_sample_type &= ~PERF_SAMPLE_BRANCH_HW_INDEX;
> retry_sample_id:
> if (perf_missing_features.sample_id_all)
> evsel->core.attr.sample_id_all = 0;
> @@ -1784,7 +1788,12 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
> * Must probe features in the order they were added to the
> * perf_event_attr interface.
> */
> - if (!perf_missing_features.aux_output && evsel->core.attr.aux_output) {
> + if (!perf_missing_features.branch_hw_idx &&
> + (evsel->core.attr.branch_sample_type & PERF_SAMPLE_BRANCH_HW_INDEX)) {
> + perf_missing_features.branch_hw_idx = true;
> + pr_debug2("switching off branch HW index support\n");
> + goto fallback_missing_features;
> + } else if (!perf_missing_features.aux_output && evsel->core.attr.aux_output) {
> perf_missing_features.aux_output = true;
> pr_debug2_peo("Kernel has no attr.aux_output support, bailing out\n");
> goto out_close;
> diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
> index 99a0cb60c556..33804740e2ca 100644
> --- a/tools/perf/util/evsel.h
> +++ b/tools/perf/util/evsel.h
> @@ -119,6 +119,7 @@ struct perf_missing_features {
> bool ksymbol;
> bool bpf;
> bool aux_output;
> + bool branch_hw_idx;
> };
>
> extern struct perf_missing_features perf_missing_features;
> diff --git a/tools/perf/util/perf_event_attr_fprintf.c b/tools/perf/util/perf_event_attr_fprintf.c
> index 651203126c71..355d3458d4e6 100644
> --- a/tools/perf/util/perf_event_attr_fprintf.c
> +++ b/tools/perf/util/perf_event_attr_fprintf.c
> @@ -50,6 +50,7 @@ static void __p_branch_sample_type(char *buf, size_t size, u64 value)
> bit_name(ABORT_TX), bit_name(IN_TX), bit_name(NO_TX),
> bit_name(COND), bit_name(CALL_STACK), bit_name(IND_JUMP),
> bit_name(CALL), bit_name(NO_FLAGS), bit_name(NO_CYCLES),
> + bit_name(HW_INDEX),
> { .name = NULL, }
> };
> #undef bit_name
> --
> 2.17.1
>
--
- Arnaldo
next prev parent reply other threads:[~2020-03-05 20:25 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-28 16:29 [PATCH 00/12] Stitch LBR call stack (Perf Tools) kan.liang
2020-02-28 16:30 ` [PATCH 01/12] perf tools: Add hw_idx in struct branch_stack kan.liang
2020-03-04 13:49 ` Arnaldo Carvalho de Melo
2020-03-04 15:45 ` Arnaldo Carvalho de Melo
2020-03-04 16:07 ` Liang, Kan
2020-03-19 14:10 ` [tip: perf/core] tools headers UAPI: Update tools's copy of linux/perf_event.h tip-bot2 for Arnaldo Carvalho de Melo
2020-03-10 0:42 ` [PATCH 01/12] perf tools: Add hw_idx in struct branch_stack Arnaldo Carvalho de Melo
2020-03-10 12:53 ` Liang, Kan
2020-03-19 14:10 ` [tip: perf/core] " tip-bot2 for Kan Liang
2020-02-28 16:30 ` [PATCH 02/12] perf tools: Support PERF_SAMPLE_BRANCH_HW_INDEX kan.liang
2020-03-05 20:25 ` Arnaldo Carvalho de Melo [this message]
2020-03-05 21:02 ` Liang, Kan
2020-03-05 23:17 ` Arnaldo Carvalho de Melo
2020-03-19 14:10 ` [tip: perf/core] perf evsel: " tip-bot2 for Kan Liang
2020-02-28 16:30 ` [PATCH 03/12] perf header: Add check for event attr kan.liang
2020-03-19 14:10 ` [tip: perf/core] perf header: Add check for unexpected use of reserved membrs in " tip-bot2 for Kan Liang
2020-02-28 16:30 ` [PATCH 04/12] perf pmu: Add support for PMU capabilities kan.liang
2020-02-28 16:30 ` [PATCH 05/12] perf header: Support CPU " kan.liang
2020-02-28 16:30 ` [PATCH 06/12] perf machine: Refine the function for LBR call stack reconstruction kan.liang
2020-02-28 16:30 ` [PATCH 07/12] perf tools: Stitch LBR call stack kan.liang
2020-02-28 16:30 ` [PATCH 08/12] perf report: Add option to enable the LBR stitching approach kan.liang
2020-02-28 16:30 ` [PATCH 09/12] perf script: " kan.liang
2020-02-28 16:30 ` [PATCH 10/12] perf top: " kan.liang
2020-02-28 16:30 ` [PATCH 11/12] perf c2c: " kan.liang
2020-02-28 16:30 ` [PATCH 12/12] perf hist: Add fast path for duplicate entries check approach kan.liang
2020-03-04 13:33 ` [PATCH 00/12] Stitch LBR call stack (Perf Tools) Arnaldo Carvalho de Melo
2020-03-06 9:39 ` Jiri Olsa
2020-03-06 19:13 ` Liang, Kan
2020-03-06 20:06 ` Arnaldo Carvalho de Melo
2020-03-09 13:27 ` Arnaldo Carvalho de Melo
2020-03-09 13:42 ` Liang, Kan
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