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Message-ID: <Z0YChjympWOZeu1e@x1>
Date: Tue, 26 Nov 2024 14:16:54 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Adrian Hunter <adrian.hunter@...el.com>
Cc: Namhyung Kim <namhyung@...nel.org>, Jiri Olsa <jolsa@...nel.org>,
Ian Rogers <irogers@...gle.com>,
Kan Liang <kan.liang@...ux.intel.com>, Leo Yan <leo.yan@....com>,
linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org
Subject: Re: [PATCH V15 0/7] perf/core: Add ability for an event to "pause"
or "resume" AUX area tracing
On Tue, Nov 26, 2024 at 02:59:02PM +0200, Adrian Hunter wrote:
> On 14/11/24 12:17, Adrian Hunter wrote:
> > Hi
> >
> > Note for V15:
> > Same as V14 but without kernel patches because they have been
> > applied, and updated "missing_features" patch for the new way
> > of detecting missing features.
>
> Still apply
So the kernel part is in, I'll go over this after getting a machine with
a kernel with those features so that I can test it all together.
- Arnaldo
> > Hardware traces, such as instruction traces, can produce a vast amount of
> > trace data, so being able to reduce tracing to more specific circumstances
> > can be useful.
> >
> > The ability to pause or resume tracing when another event happens, can do
> > that.
> >
> > These patches add such a facilty and show how it would work for Intel
> > Processor Trace.
> >
> > Maintainers of other AUX area tracing implementations are requested to
> > consider if this is something they might employ and then whether or not
> > the ABI would work for them. Note, thank you to James Clark (ARM) for
> > evaluating the API for Coresight. Suzuki K Poulose (ARM) also responded
> > positively to the RFC.
> >
> > Changes to perf tools are now (since V4) fleshed out.
> >
> > Please note, Intel® Architecture Instruction Set Extensions and Future
> > Features Programming Reference March 2024 319433-052, currently:
> >
> > https://cdrdv2.intel.com/v1/dl/getContent/671368
> >
> > introduces hardware pause / resume for Intel PT in a feature named
> > Intel PT Trigger Tracing.
> >
> > For that more fields in perf_event_attr will be necessary. The main
> > differences are:
> > - it can be applied not just to overflows, but optionally to
> > every event
> > - a packet is emitted into the trace, optionally with IP
> > information
> > - no PMI
> > - works with PMC and DR (breakpoint) events only
> >
> > Here are the proposed additions to perf_event_attr, please comment:
> >
> > diff --git a/tools/include/uapi/linux/perf_event.h b/tools/include/uapi/linux/perf_event.h
> > index 0c557f0a17b3..05dcc43f11bb 100644
> > --- a/tools/include/uapi/linux/perf_event.h
> > +++ b/tools/include/uapi/linux/perf_event.h
> > @@ -369,6 +369,22 @@ enum perf_event_read_format {
> > PERF_FORMAT_MAX = 1U << 5, /* non-ABI */
> > };
> >
> > +enum {
> > + PERF_AUX_ACTION_START_PAUSED = 1U << 0,
> > + PERF_AUX_ACTION_PAUSE = 1U << 1,
> > + PERF_AUX_ACTION_RESUME = 1U << 2,
> > + PERF_AUX_ACTION_EMIT = 1U << 3,
> > + PERF_AUX_ACTION_NR = 0x1f << 4,
> > + PERF_AUX_ACTION_NO_IP = 1U << 9,
> > + PERF_AUX_ACTION_PAUSE_ON_EVT = 1U << 10,
> > + PERF_AUX_ACTION_RESUME_ON_EVT = 1U << 11,
> > + PERF_AUX_ACTION_EMIT_ON_EVT = 1U << 12,
> > + PERF_AUX_ACTION_NR_ON_EVT = 0x1f << 13,
> > + PERF_AUX_ACTION_NO_IP_ON_EVT = 1U << 18,
> > + PERF_AUX_ACTION_MASK = ~PERF_AUX_ACTION_START_PAUSED,
> > + PERF_AUX_PAUSE_RESUME_MASK = PERF_AUX_ACTION_PAUSE | PERF_AUX_ACTION_RESUME,
> > +};
> > +
> > #define PERF_ATTR_SIZE_VER0 64 /* sizeof first published struct */
> > #define PERF_ATTR_SIZE_VER1 72 /* add: config2 */
> > #define PERF_ATTR_SIZE_VER2 80 /* add: branch_sample_type */
> > @@ -515,10 +531,19 @@ struct perf_event_attr {
> > union {
> > __u32 aux_action;
> > struct {
> > - __u32 aux_start_paused : 1, /* start AUX area tracing paused */
> > - aux_pause : 1, /* on overflow, pause AUX area tracing */
> > - aux_resume : 1, /* on overflow, resume AUX area tracing */
> > - __reserved_3 : 29;
> > + __u32 aux_start_paused : 1, /* start AUX area tracing paused */
> > + aux_pause : 1, /* on overflow, pause AUX area tracing */
> > + aux_resume : 1, /* on overflow, resume AUX area tracing */
> > + aux_emit : 1, /* generate AUX records instead of events */
> > + aux_nr : 5, /* AUX area tracing reference number */
> > + aux_no_ip : 1, /* suppress IP in AUX records */
> > + /* Following apply to event occurrence not overflows */
> > + aux_pause_on_evt : 1, /* on event, pause AUX area tracing */
> > + aux_resume_on_evt : 1, /* on event, resume AUX area tracing */
> > + aux_emit_on_evt : 1, /* generate AUX records instead of events */
> > + aux_nr_on_evt : 5, /* AUX area tracing reference number */
> > + aux_no_ip_on_evt : 1, /* suppress IP in AUX records */
> > + __reserved_3 : 13;
> > };
> > };
> >
> >
> > Changes in V15:
> > perf/x86/intel/pt: Fix buffer full but size is 0 case
> > perf/core: Add aux_pause, aux_resume, aux_start_paused
> > perf/x86/intel/pt: Add support for pause / resume
> > perf/x86/intel: Do not enable large PEBS for events with aux actions or aux sampling
> > Dropped kernel patches because they have been applied
> >
> > perf tools: Add missing_features for aux_start_paused, aux_pause, aux_resume
> > Re-base on new API probe method of missing feature detection
> > and add probe for aux_action.
> >
> > Changes in V14:
> > Dropped KVM patches
> >
> > perf/x86/intel/pt: Add support for pause / resume
> > Set pt->handle_nmi after configuration is completed instead of during
> >
> > Changes in V13:
> > perf/core: Add aux_pause, aux_resume, aux_start_paused
> > Do aux_resume at the end of __perf_event_overflow() so as to trace
> > less of perf itself
> >
> > perf tools: Add missing_features for aux_start_paused, aux_pause, aux_resume
> > Add error message also in EOPNOTSUPP case (Leo)
> >
> > Changes in V12:
> > Add previously sent patch "perf/x86/intel/pt: Fix buffer full
> > but size is 0 case"
> >
> > Add previously sent patch set "KVM: x86: Fix Intel PT Host/Guest
> > mode when host tracing"
> >
> > Rebase on current tip plus patch set "KVM: x86: Fix Intel PT Host/Guest
> > mode when host tracing"
> >
> > Changes in V11:
> > perf/core: Add aux_pause, aux_resume, aux_start_paused
> > Make assignment to event->hw.aux_paused conditional on
> > (pmu->capabilities & PERF_PMU_CAP_AUX_PAUSE).
> >
> > perf/x86/intel: Do not enable large PEBS for events with aux actions or aux sampling
> > Remove definition of has_aux_action() because it has
> > already been added as an inline function.
> >
> > perf/x86/intel/pt: Fix sampling synchronization
> > perf tools: Enable evsel__is_aux_event() to work for ARM/ARM64
> > perf tools: Enable evsel__is_aux_event() to work for S390_CPUMSF
> > Dropped because they have already been applied
> >
> > Changes in V10:
> > perf/core: Add aux_pause, aux_resume, aux_start_paused
> > Move aux_paused into a union within struct hw_perf_event.
> > Additional comment wrt PERF_EF_PAUSE/PERF_EF_RESUME.
> > Factor out has_aux_action() as an inline function.
> > Use scoped_guard for irqsave.
> > Move calls of perf_event_aux_pause() from __perf_event_output()
> > to __perf_event_overflow().
> >
> > Changes in V9:
> > perf/x86/intel/pt: Fix sampling synchronization
> > New patch
> >
> > perf/core: Add aux_pause, aux_resume, aux_start_paused
> > Move aux_paused to struct hw_perf_event
> >
> > perf/x86/intel/pt: Add support for pause / resume
> > Add more comments and barriers for resume_allowed and
> > pause_allowed
> > Always use WRITE_ONCE with resume_allowed
> >
> >
> > Changes in V8:
> >
> > perf tools: Parse aux-action
> > Fix clang warning:
> > util/auxtrace.c:821:7: error: missing field 'aux_action' initializer [-Werror,-Wmissing-field-initializers]
> > 821 | {NULL},
> > | ^
> >
> > Changes in V7:
> >
> > Add Andi's Reviewed-by for patches 2-12
> > Re-base
> >
> > Changes in V6:
> >
> > perf/core: Add aux_pause, aux_resume, aux_start_paused
> > Removed READ/WRITE_ONCE from __perf_event_aux_pause()
> > Expanded comment about guarding against NMI
> >
> > Changes in V5:
> >
> > perf/core: Add aux_pause, aux_resume, aux_start_paused
> > Added James' Ack
> >
> > perf/x86/intel: Do not enable large PEBS for events with aux actions or aux sampling
> > New patch
> >
> > perf tools
> > Added Ian's Ack
> >
> > Changes in V4:
> >
> > perf/core: Add aux_pause, aux_resume, aux_start_paused
> > Rename aux_output_cfg -> aux_action
> > Reorder aux_action bits from:
> > aux_pause, aux_resume, aux_start_paused
> > to:
> > aux_start_paused, aux_pause, aux_resume
> > Fix aux_action bits __u64 -> __u32
> >
> > coresight: Have a stab at support for pause / resume
> > Dropped
> >
> > perf tools
> > All new patches
> >
> > Changes in RFC V3:
> >
> > coresight: Have a stab at support for pause / resume
> > 'mode' -> 'flags' so it at least compiles
> >
> > Changes in RFC V2:
> >
> > Use ->stop() / ->start() instead of ->pause_resume()
> > Move aux_start_paused bit into aux_output_cfg
> > Tighten up when Intel PT pause / resume is allowed
> > Add an example of how it might work for CoreSight
> >
> >
> > Adrian Hunter (7):
> > perf tools: Add aux_start_paused, aux_pause and aux_resume
> > perf tools: Add aux-action config term
> > perf tools: Parse aux-action
> > perf tools: Add missing_features for aux_start_paused, aux_pause, aux_resume
> > perf intel-pt: Improve man page format
> > perf intel-pt: Add documentation for pause / resume
> > perf intel-pt: Add a test for pause / resume
> >
> > tools/include/uapi/linux/perf_event.h | 11 +-
> > tools/perf/Documentation/perf-intel-pt.txt | 596 ++++++++++++++++++-----------
> > tools/perf/Documentation/perf-record.txt | 4 +
> > tools/perf/builtin-record.c | 4 +-
> > tools/perf/tests/shell/test_intel_pt.sh | 28 ++
> > tools/perf/util/auxtrace.c | 67 +++-
> > tools/perf/util/auxtrace.h | 6 +-
> > tools/perf/util/evsel.c | 101 ++++-
> > tools/perf/util/evsel.h | 1 +
> > tools/perf/util/evsel_config.h | 1 +
> > tools/perf/util/parse-events.c | 10 +
> > tools/perf/util/parse-events.h | 1 +
> > tools/perf/util/parse-events.l | 1 +
> > tools/perf/util/perf_event_attr_fprintf.c | 3 +
> > tools/perf/util/pmu.c | 1 +
> > 15 files changed, 594 insertions(+), 241 deletions(-)
> >
> >
> > Regards
> > Adrian
>
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