[tip: perf/core] perf intel-pt: Add support for recording AUX area samples

From: tip-bot2 for Adrian Hunter
Date: Sat Nov 23 2019 - 03:16:09 EST

Next message: tip-bot2 for Adrian Hunter: "[tip: perf/core] perf record: Add aux-sample-size config term"
Previous message: tip-bot2 for Adrian Hunter: "[tip: perf/core] perf tools: Add kernel AUX area sampling definitions"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

The following commit has been merged into the perf/core branch of tip:

Commit-ID: c4ab2f0f763da64d88cec6f20fd664f2347eca60
Gitweb: https://git.kernel.org/tip/c4ab2f0f763da64d88cec6f20fd664f2347eca60
Author: Adrian Hunter <adrian.hunter@xxxxxxxxx>
AuthorDate: Fri, 15 Nov 2019 14:42:23 +02:00
Committer: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitterDate: Fri, 22 Nov 2019 10:48:13 -03:00

perf intel-pt: Add support for recording AUX area samples

Set up the default number of mmap pages, default sample size and default
psb_period for AUX area sampling. Add documentation also.

Signed-off-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Link: http://lore.kernel.org/lkml/20191115124225.5247-14-adrian.hunter@xxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
tools/perf/Documentation/intel-pt.txt | 59 ++++++++++++++++++-
tools/perf/arch/x86/util/auxtrace.c | 2 +-
tools/perf/arch/x86/util/intel-pt.c | 81 +++++++++++++++++++++++++-
3 files changed, 139 insertions(+), 3 deletions(-)

diff --git a/tools/perf/Documentation/intel-pt.txt b/tools/perf/Documentation/intel-pt.txt
index e0d9e7d..2cf2d9e 100644
--- a/tools/perf/Documentation/intel-pt.txt
+++ b/tools/perf/Documentation/intel-pt.txt
@@ -434,6 +434,56 @@ pwr_evt Enable power events. The power events provide information about
"0" otherwise.

+AUX area sampling option
+------------------------
+
+To select Intel PT "sampling" the AUX area sampling option can be used:
+
+ --aux-sample
+
+Optionally it can be followed by the sample size in bytes e.g.
+
+ --aux-sample=8192
+
+In addition, the Intel PT event to sample must be defined e.g.
+
+ -e intel_pt//u
+
+Samples on other events will be created containing Intel PT data e.g. the
+following will create Intel PT samples on the branch-misses event, note the
+events must be grouped using {}:
+
+ perf record --aux-sample -e '{intel_pt//u,branch-misses:u}'
+
+An alternative to '--aux-sample' is to add the config term 'aux-sample-size' to
+events. In this case, the grouping is implied e.g.
+
+ perf record -e intel_pt//u -e branch-misses/aux-sample-size=8192/u
+
+is the same as:
+
+ perf record -e '{intel_pt//u,branch-misses/aux-sample-size=8192/u}'
+
+but allows for also using an address filter e.g.:
+
+ perf record -e intel_pt//u --filter 'filter * @/bin/ls' -e branch-misses/aux-sample-size=8192/u -- ls
+
+It is important to select a sample size that is big enough to contain at least
+one PSB packet. If not a warning will be displayed:
+
+ Intel PT sample size (%zu) may be too small for PSB period (%zu)
+
+The calculation used for that is: if sample_size <= psb_period + 256 display the
+warning. When sampling is used, psb_period defaults to 0 (2KiB).
+
+The default sample size is 4KiB.
+
+The sample size is passed in aux_sample_size in struct perf_event_attr. The
+sample size is limited by the maximum event size which is 64KiB. It is
+difficult to know how big the event might be without the trace sample attached,
+but the tool validates that the sample size is not greater than 60KiB.
+
+
new snapshot option
-------------------

@@ -487,8 +537,8 @@ their mlock limit (which defaults to 64KiB but is not multiplied by the number
of cpus).

In full-trace mode, powers of two are allowed for buffer size, with a minimum
-size of 2 pages. In snapshot mode, it is the same but the minimum size is
-1 page.
+size of 2 pages. In snapshot mode or sampling mode, it is the same but the
+minimum size is 1 page.

The mmap size and auxtrace mmap size are displayed if the -vv option is used e.g.

@@ -501,12 +551,17 @@ Intel PT modes of operation

Intel PT can be used in 2 modes:
full-trace mode
+ sample mode
snapshot mode

Full-trace mode traces continuously e.g.

perf record -e intel_pt//u uname

+Sample mode attaches a Intel PT sample to other events e.g.
+
+ perf record --aux-sample -e intel_pt//u -e branch-misses:u
+
Snapshot mode captures the available data when a signal is sent e.g.

perf record -v -e intel_pt//u -S ./loopy 1000000000 &
diff --git a/tools/perf/arch/x86/util/auxtrace.c b/tools/perf/arch/x86/util/auxtrace.c
index 96f4a2c..092543c 100644
--- a/tools/perf/arch/x86/util/auxtrace.c
+++ b/tools/perf/arch/x86/util/auxtrace.c
@@ -26,6 +26,8 @@ struct auxtrace_record *auxtrace_record__init_intel(struct evlist *evlist,
bool found_bts = false;

intel_pt_pmu = perf_pmu__find(INTEL_PT_PMU_NAME);
+ if (intel_pt_pmu)
+ intel_pt_pmu->auxtrace = true;
intel_bts_pmu = perf_pmu__find(INTEL_BTS_PMU_NAME);

evlist__for_each_entry(evlist, evsel) {
diff --git a/tools/perf/arch/x86/util/intel-pt.c b/tools/perf/arch/x86/util/intel-pt.c
index d6d2625..20df442 100644
--- a/tools/perf/arch/x86/util/intel-pt.c
+++ b/tools/perf/arch/x86/util/intel-pt.c
@@ -17,6 +17,7 @@
#include "../../util/event.h"
#include "../../util/evlist.h"
#include "../../util/evsel.h"
+#include "../../util/evsel_config.h"
#include "../../util/cpumap.h"
#include "../../util/mmap.h"
#include <subcmd/parse-options.h>
@@ -551,6 +552,43 @@ static int intel_pt_validate_config(struct perf_pmu *intel_pt_pmu,
evsel->core.attr.config);
}

+static void intel_pt_config_sample_mode(struct perf_pmu *intel_pt_pmu,
+ struct evsel *evsel)
+{
+ struct perf_evsel_config_term *term;
+ u64 user_bits = 0, bits;
+
+ term = perf_evsel__get_config_term(evsel, CFG_CHG);
+ if (term)
+ user_bits = term->val.cfg_chg;
+
+ bits = perf_pmu__format_bits(&intel_pt_pmu->format, "psb_period");
+
+ /* Did user change psb_period */
+ if (bits & user_bits)
+ return;
+
+ /* Set psb_period to 0 */
+ evsel->core.attr.config &= ~bits;
+}
+
+static void intel_pt_min_max_sample_sz(struct evlist *evlist,
+ size_t *min_sz, size_t *max_sz)
+{
+ struct evsel *evsel;
+
+ evlist__for_each_entry(evlist, evsel) {
+ size_t sz = evsel->core.attr.aux_sample_size;
+
+ if (!sz)
+ continue;
+ if (min_sz && (sz < *min_sz || !*min_sz))
+ *min_sz = sz;
+ if (max_sz && sz > *max_sz)
+ *max_sz = sz;
+ }
+}
+
/*
* Currently, there is not enough information to disambiguate different PEBS
* events, so only allow one.
@@ -606,6 +644,11 @@ static int intel_pt_recording_options(struct auxtrace_record *itr,
return -EINVAL;
}

+ if (opts->auxtrace_snapshot_mode && opts->auxtrace_sample_mode) {
+ pr_err("Snapshot mode (" INTEL_PT_PMU_NAME " PMU) and sample trace cannot be used together\n");
+ return -EINVAL;
+ }
+
if (opts->use_clockid) {
pr_err("Cannot use clockid (-k option) with " INTEL_PT_PMU_NAME "\n");
return -EINVAL;
@@ -617,6 +660,9 @@ static int intel_pt_recording_options(struct auxtrace_record *itr,
if (!opts->full_auxtrace)
return 0;

+ if (opts->auxtrace_sample_mode)
+ intel_pt_config_sample_mode(intel_pt_pmu, intel_pt_evsel);
+
err = intel_pt_validate_config(intel_pt_pmu, intel_pt_evsel);
if (err)
return err;
@@ -666,6 +712,34 @@ static int intel_pt_recording_options(struct auxtrace_record *itr,
opts->auxtrace_snapshot_size, psb_period);
}

+ /* Set default sizes for sample mode */
+ if (opts->auxtrace_sample_mode) {
+ size_t psb_period = intel_pt_psb_period(intel_pt_pmu, evlist);
+ size_t min_sz = 0, max_sz = 0;
+
+ intel_pt_min_max_sample_sz(evlist, &min_sz, &max_sz);
+ if (!opts->auxtrace_mmap_pages && !privileged &&
+ opts->mmap_pages == UINT_MAX)
+ opts->mmap_pages = KiB(256) / page_size;
+ if (!opts->auxtrace_mmap_pages) {
+ size_t sz = round_up(max_sz, page_size) / page_size;
+
+ opts->auxtrace_mmap_pages = roundup_pow_of_two(sz);
+ }
+ if (max_sz > opts->auxtrace_mmap_pages * (size_t)page_size) {
+ pr_err("Sample size %zu must not be greater than AUX area tracing mmap size %zu\n",
+ max_sz,
+ opts->auxtrace_mmap_pages * (size_t)page_size);
+ return -EINVAL;
+ }
+ pr_debug2("Intel PT min. sample size: %zu max. sample size: %zu\n",
+ min_sz, max_sz);
+ if (psb_period &&
+ min_sz <= psb_period + INTEL_PT_PSB_PERIOD_NEAR)
+ ui__warning("Intel PT sample size (%zu) may be too small for PSB period (%zu)\n",
+ min_sz, psb_period);
+ }
+
/* Set default sizes for full trace mode */
if (opts->full_auxtrace && !opts->auxtrace_mmap_pages) {
if (privileged) {
@@ -682,7 +756,7 @@ static int intel_pt_recording_options(struct auxtrace_record *itr,
size_t sz = opts->auxtrace_mmap_pages * (size_t)page_size;
size_t min_sz;

- if (opts->auxtrace_snapshot_mode)
+ if (opts->auxtrace_snapshot_mode || opts->auxtrace_sample_mode)
min_sz = KiB(4);
else
min_sz = KiB(8);
@@ -1136,5 +1210,10 @@ struct auxtrace_record *intel_pt_recording_init(int *err)
ptr->itr.parse_snapshot_options = intel_pt_parse_snapshot_options;
ptr->itr.reference = intel_pt_reference;
ptr->itr.read_finish = intel_pt_read_finish;
+ /*
+ * Decoding starts at a PSB packet. Minimum PSB period is 2K so 4K
+ * should give at least 1 PSB per sample.
+ */
+ ptr->itr.default_aux_sample_size = 4096;
return &ptr->itr;
}

Next message: tip-bot2 for Adrian Hunter: "[tip: perf/core] perf record: Add aux-sample-size config term"
Previous message: tip-bot2 for Adrian Hunter: "[tip: perf/core] perf tools: Add kernel AUX area sampling definitions"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]