Re: [PATCH 1/5] perf, tools: Add support for skipping itrace instructions

Adrian Hunter
2016-03-29T17:33:55Z

On 29/03/2016 7:27 p.m., Arnaldo Carvalho de Melo wrote:
> Em Mon, Mar 28, 2016 at 10:45:38AM -0700, Andi Kleen escreveu:
>> From: Andi Kleen <ak@linux.intel.com>
>>
>> When using perf script to look at PT traces it is often
>> useful to ignore the initialization code at the beginning.
>>
>> On larger traces which may have many millions of instructions
>> in initialization code doing that in a pipeline can be very
>> slow, with perf script spending a lot of CPU time calling
>> printf and writing data.
>>
>> This patch adds an extension to the --itrace argument
>> that skips 'n' events (instructions, branches or transactions)
>> at the beginning. This is much more efficient.
>>
>> Cc: Adrian Hunter <adrian.hunter@intel.com>
>
> Adrian, are you ok now? Can I have your Acked-by?

The last hunk isn't actually needed, but apart from that:

Acked-by: Adrian Hunter <adrian.hunter@intel.com>

>
> - Arnaldo
>
>> v2:
>> Add support for BTS (Adrian Hunter)
>> Document in itrace.txt
>> Fix branch check
>> Check transactions and instructions too
>> Signed-off-by: Andi Kleen <ak@linux.intel.com>
>> ---
>> tools/perf/Documentation/intel-pt.txt | 7 +++++++
>> tools/perf/Documentation/itrace.txt | 8 ++++++++
>> tools/perf/util/auxtrace.c | 7 +++++++
>> tools/perf/util/auxtrace.h | 2 ++
>> tools/perf/util/intel-bts.c | 5 +++++
>> tools/perf/util/intel-pt.c | 22 ++++++++++++++++++++--
>> 6 files changed, 49 insertions(+), 2 deletions(-)
>>
>> diff --git a/tools/perf/Documentation/intel-pt.txt b/tools/perf/Documentation/intel-pt.txt
>> index be764f9..c6c8318 100644
>> --- a/tools/perf/Documentation/intel-pt.txt
>> +++ b/tools/perf/Documentation/intel-pt.txt
>> @@ -672,6 +672,7 @@ The letters are:
>> d create a debug log
>> g synthesize a call chain (use with i or x)
>> l synthesize last branch entries (use with i or x)
>> + s skip initial number of events
>>
>> "Instructions" events look like they were recorded by "perf record -e
>> instructions".
>> @@ -730,6 +731,12 @@ from one sample to the next.
>>
>> To disable trace decoding entirely, use the option --no-itrace.
>>
>> +It is also possible to skip events generated (instructions, branches, transactions)
>> +at the beginning. This is useful to ignore initialization code.
>> +
>> + --itrace=i0nss1000000
>> +
>> +skips the first million instructions.
>>
>> dump option
>> -----------
>> diff --git a/tools/perf/Documentation/itrace.txt b/tools/perf/Documentation/itrace.txt
>> index 65453f4..e2a4c5e 100644
>> --- a/tools/perf/Documentation/itrace.txt
>> +++ b/tools/perf/Documentation/itrace.txt
>> @@ -7,6 +7,7 @@
>> d create a debug log
>> g synthesize a call chain (use with i or x)
>> l synthesize last branch entries (use with i or x)
>> + s skip initial number of events
>>
>> The default is all events i.e. the same as --itrace=ibxe
>>
>> @@ -24,3 +25,10 @@
>>
>> Also the number of last branch entries (default 64, max. 1024) for
>> instructions or transactions events can be specified.
>> +
>> + It is also possible to skip events generated (instructions, branches, transactions)
>> + at the beginning. This is useful to ignore initialization code.
>> +
>> + --itrace=i0nss1000000
>> +
>> + skips the first million instructions.
>> diff --git a/tools/perf/util/auxtrace.c b/tools/perf/util/auxtrace.c
>> index ec164fe..c916901 100644
>> --- a/tools/perf/util/auxtrace.c
>> +++ b/tools/perf/util/auxtrace.c
>> @@ -940,6 +940,7 @@ void itrace_synth_opts__set_default(struct itrace_synth_opts *synth_opts)
>> synth_opts->period = PERF_ITRACE_DEFAULT_PERIOD;
>> synth_opts->callchain_sz = PERF_ITRACE_DEFAULT_CALLCHAIN_SZ;
>> synth_opts->last_branch_sz = PERF_ITRACE_DEFAULT_LAST_BRANCH_SZ;
>> + synth_opts->initial_skip = 0;
>> }
>>
>> /*
>> @@ -1064,6 +1065,12 @@ int itrace_parse_synth_opts(const struct option *opt, const char *str,
>> synth_opts->last_branch_sz = val;
>> }
>> break;
>> + case 's':
>> + synth_opts->initial_skip = strtoul(p, &endptr, 10);
>> + if (p == endptr)
>> + goto out_err;
>> + p = endptr;
>> + break;
>> case ' ':
>> case ',':
>> break;
>> diff --git a/tools/perf/util/auxtrace.h b/tools/perf/util/auxtrace.h
>> index 57ff31e..767989e 100644
>> --- a/tools/perf/util/auxtrace.h
>> +++ b/tools/perf/util/auxtrace.h
>> @@ -68,6 +68,7 @@ enum itrace_period_type {
>> * @last_branch_sz: branch context size
>> * @period: 'instructions' events period
>> * @period_type: 'instructions' events period type
>> + * @initial_skip: skip N events at the beginning.
>> */
>> struct itrace_synth_opts {
>> bool set;
>> @@ -86,6 +87,7 @@ struct itrace_synth_opts {
>> unsigned int last_branch_sz;
>> unsigned long long period;
>> enum itrace_period_type period_type;
>> + unsigned long initial_skip;
>> };
>>
>> /**
>> diff --git a/tools/perf/util/intel-bts.c b/tools/perf/util/intel-bts.c
>> index 6bc3ecd..3ff2f72f 100644
>> --- a/tools/perf/util/intel-bts.c
>> +++ b/tools/perf/util/intel-bts.c
>> @@ -66,6 +66,7 @@ struct intel_bts {
>> u64 branches_id;
>> size_t branches_event_size;
>> bool synth_needs_swap;
>> + unsigned long num_events;
>> };
>>
>> struct intel_bts_queue {
>> @@ -275,6 +276,10 @@ static int intel_bts_synth_branch_sample(struct intel_bts_queue *btsq,
>> union perf_event event;
>> struct perf_sample sample = { .ip = 0, };
>>
>> + if (bts->synth_opts.initial_skip &&
>> + bts->num_events++ <= bts->synth_opts.initial_skip)
>> + return 0;
>> +
>> event.sample.header.type = PERF_RECORD_SAMPLE;
>> event.sample.header.misc = PERF_RECORD_MISC_USER;
>> event.sample.header.size = sizeof(struct perf_event_header);
>> diff --git a/tools/perf/util/intel-pt.c b/tools/perf/util/intel-pt.c
>> index 05d8158..07f0020 100644
>> --- a/tools/perf/util/intel-pt.c
>> +++ b/tools/perf/util/intel-pt.c
>> @@ -100,6 +100,8 @@ struct intel_pt {
>> u64 cyc_bit;
>> u64 noretcomp_bit;
>> unsigned max_non_turbo_ratio;
>> +
>> + unsigned long num_events;
>> };
>>
>> enum switch_state {
>> @@ -972,6 +974,10 @@ static int intel_pt_synth_branch_sample(struct intel_pt_queue *ptq)
>> if (pt->branches_filter && !(pt->branches_filter & ptq->flags))
>> return 0;
>>
>> + if (pt->synth_opts.initial_skip &&
>> + pt->num_events++ < pt->synth_opts.initial_skip)
>> + return 0;
>> +
>> event->sample.header.type = PERF_RECORD_SAMPLE;
>> event->sample.header.misc = PERF_RECORD_MISC_USER;
>> event->sample.header.size = sizeof(struct perf_event_header);
>> @@ -1028,6 +1034,10 @@ static int intel_pt_synth_instruction_sample(struct intel_pt_queue *ptq)
>> union perf_event *event = ptq->event_buf;
>> struct perf_sample sample = { .ip = 0, };
>>
>> + if (pt->synth_opts.initial_skip &&
>> + pt->num_events++ < pt->synth_opts.initial_skip)
>> + return 0;
>> +
>> event->sample.header.type = PERF_RECORD_SAMPLE;
>> event->sample.header.misc = PERF_RECORD_MISC_USER;
>> event->sample.header.size = sizeof(struct perf_event_header);
>> @@ -1085,6 +1095,10 @@ static int intel_pt_synth_transaction_sample(struct intel_pt_queue *ptq)
>> union perf_event *event = ptq->event_buf;
>> struct perf_sample sample = { .ip = 0, };
>>
>> + if (pt->synth_opts.initial_skip &&
>> + pt->num_events++ < pt->synth_opts.initial_skip)
>> + return 0;
>> +
>> event->sample.header.type = PERF_RECORD_SAMPLE;
>> event->sample.header.misc = PERF_RECORD_MISC_USER;
>> event->sample.header.size = sizeof(struct perf_event_header);
>> @@ -1196,14 +1210,18 @@ static int intel_pt_sample(struct intel_pt_queue *ptq)
>> ptq->have_sample = false;
>>
>> if (pt->sample_instructions &&
>> - (state->type & INTEL_PT_INSTRUCTION)) {
>> + (state->type & INTEL_PT_INSTRUCTION) &&
>> + (!pt->synth_opts.initial_skip ||
>> + pt->num_events++ >= pt->synth_opts.initial_skip)) {
>> err = intel_pt_synth_instruction_sample(ptq);
>> if (err)
>> return err;
>> }
>>
>> if (pt->sample_transactions &&
>> - (state->type & INTEL_PT_TRANSACTION)) {
>> + (state->type & INTEL_PT_TRANSACTION) &&
>> + (!pt->synth_opts.initial_skip ||
>> + pt->num_events++ >= pt->synth_opts.initial_skip)) {
>> err = intel_pt_synth_transaction_sample(ptq);
>> if (err)
>> return err;

This last hunk (@@ -1196,14 +1210,18 @@) isn't needed since
intel_pt_synth_instruction_sample() and
intel_pt_synth_transaction_sample() check initial_skip themselves.