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Message-ID: <56127eee-6fdc-8f77-59e0-23fbed311af8@huawei.com>
Date: Fri, 25 Aug 2023 14:05:01 +0800
From: Yang Jihong <yangjihong1@...wei.com>
To: Ian Rogers <irogers@...gle.com>
CC: <peterz@...radead.org>, <mingo@...hat.com>, <acme@...nel.org>,
<mark.rutland@....com>, <alexander.shishkin@...ux.intel.com>,
<jolsa@...nel.org>, <namhyung@...nel.org>,
<adrian.hunter@...el.com>, <kan.liang@...ux.intel.com>,
<james.clark@....com>, <tmricht@...ux.ibm.com>,
<ak@...ux.intel.com>, <anshuman.khandual@....com>,
<linux-kernel@...r.kernel.org>, <linux-perf-users@...r.kernel.org>
Subject: Re: [PATCH v6 3/7] perf record: Move setting dummy tracking before
record__init_thread_masks()
Hello,
On 2023/8/25 13:10, Ian Rogers wrote:
> On Sun, Aug 20, 2023 at 6:30 PM Yang Jihong <yangjihong1@...wei.com> wrote:
>>
>> User space tasks can migrate between CPUs, so when tracing selected CPUs,
>> sideband for all CPUs is needed. In this case set the cpu map of the evsel
>> to all online CPUs. This may modify the original cpu map of the evlist.
>> Therefore, need to check whether the preceding scenario exists before
>> record__init_thread_masks().
>> Dummy tracking has been set in record__open(), move it before
>> record__init_thread_masks() and add a helper for unified processing.
>
> I have a hard time understanding this commit message. Let me have a go:
>
> In order to set cpu maps correctly on dummy events they need to set up
> later. Factor out the dummy event initialization from record__open and
> move it to its own function record__setup_dummy_event. Move the call
> to the record__setup_dummy to before the call to
> record__init_thread_masks in cmd_record.
Yes, as you said above, for that purpose
>
>> The sys_perf_event_open invoked is as follows:
>>
>> # perf --debug verbose=3 record -e cpu-clock -D 100 true
>> <SNIP>
>> Opening: cpu-clock
>> ------------------------------------------------------------
>> perf_event_attr:
>> type 1 (PERF_TYPE_SOFTWARE)
>> size 136
>> config 0 (PERF_COUNT_SW_CPU_CLOCK)
>> { sample_period, sample_freq } 4000
>> sample_type IP|TID|TIME|PERIOD|IDENTIFIER
>> read_format ID|LOST
>> disabled 1
>> inherit 1
>> freq 1
>> sample_id_all 1
>> exclude_guest 1
>> ------------------------------------------------------------
>> sys_perf_event_open: pid 10318 cpu 0 group_fd -1 flags 0x8 = 5
>> sys_perf_event_open: pid 10318 cpu 1 group_fd -1 flags 0x8 = 6
>> sys_perf_event_open: pid 10318 cpu 2 group_fd -1 flags 0x8 = 7
>> sys_perf_event_open: pid 10318 cpu 3 group_fd -1 flags 0x8 = 9
>> sys_perf_event_open: pid 10318 cpu 4 group_fd -1 flags 0x8 = 10
>> sys_perf_event_open: pid 10318 cpu 5 group_fd -1 flags 0x8 = 11
>> sys_perf_event_open: pid 10318 cpu 6 group_fd -1 flags 0x8 = 12
>> sys_perf_event_open: pid 10318 cpu 7 group_fd -1 flags 0x8 = 13
>> Opening: dummy:u
>> ------------------------------------------------------------
>> perf_event_attr:
>> type 1 (PERF_TYPE_SOFTWARE)
>> size 136
>> config 0x9 (PERF_COUNT_SW_DUMMY)
>> { sample_period, sample_freq } 1
>> sample_type IP|TID|TIME|IDENTIFIER
>> read_format ID|LOST
>> disabled 1
>> inherit 1
>> exclude_kernel 1
>> exclude_hv 1
>> mmap 1
>> comm 1
>> enable_on_exec 1
>> task 1
>> sample_id_all 1
>> exclude_guest 1
>> mmap2 1
>> comm_exec 1
>> ksymbol 1
>> bpf_event 1
>> ------------------------------------------------------------
>> sys_perf_event_open: pid 10318 cpu 0 group_fd -1 flags 0x8 = 14
>> sys_perf_event_open: pid 10318 cpu 1 group_fd -1 flags 0x8 = 15
>> sys_perf_event_open: pid 10318 cpu 2 group_fd -1 flags 0x8 = 16
>> sys_perf_event_open: pid 10318 cpu 3 group_fd -1 flags 0x8 = 17
>> sys_perf_event_open: pid 10318 cpu 4 group_fd -1 flags 0x8 = 18
>> sys_perf_event_open: pid 10318 cpu 5 group_fd -1 flags 0x8 = 19
>> sys_perf_event_open: pid 10318 cpu 6 group_fd -1 flags 0x8 = 20
>> sys_perf_event_open: pid 10318 cpu 7 group_fd -1 flags 0x8 = 21
>> <SNIP>
>>
>> Signed-off-by: Yang Jihong <yangjihong1@...wei.com>
>> Acked-by: Adrian Hunter <adrian.hunter@...el.com>
>> ---
>> tools/perf/builtin-record.c | 59 +++++++++++++++++++++++--------------
>> 1 file changed, 37 insertions(+), 22 deletions(-)
>>
>> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
>> index 12edad8392cc..4ee94058028f 100644
>> --- a/tools/perf/builtin-record.c
>> +++ b/tools/perf/builtin-record.c
>> @@ -906,6 +906,37 @@ static int record__config_off_cpu(struct record *rec)
>> return off_cpu_prepare(rec->evlist, &rec->opts.target, &rec->opts);
>> }
>>
>> +static int record__config_tracking_events(struct record *rec)
>> +{
>> + struct record_opts *opts = &rec->opts;
>> + struct evlist *evlist = rec->evlist;
>> + struct evsel *evsel;
>> +
>> + /*
>> + * For initial_delay, system wide or a hybrid system, we need to add a
>> + * dummy event so that we can track PERF_RECORD_MMAP to cover the delay
>
> This code is explicitly talking about dummy events but the function is
> now renamed to call it a tracking event. I think the code should be
> consistent.
>
>> + * of waiting or event synthesis.
>> + */
>> + if (opts->target.initial_delay || target__has_cpu(&opts->target) ||
>> + perf_pmus__num_core_pmus() > 1) {
>> + evsel = evlist__findnew_tracking_event(evlist, false);
>> + if (!evsel)
>> + return -ENOMEM;
>> +
>> + /*
>> + * Enable the dummy event when the process is forked for
>
> Dummy again.
>
This comment directly copies the original content.
I can change to "tracking event" in the next version.
Thanks,
Yang
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