Messages in this thread | | | From | Alexander Shishkin <> | Subject | [PATCH v4 00/22] perf: Add infrastructure and support for Intel PT | Date | Wed, 20 Aug 2014 15:35:57 +0300 |
| |
Hi Peter and all,
This patchset adds support for Intel Processor Trace (PT) extension [1] of Intel Architecture that allows the capture of information about software execution flow, to the perf kernel infrastructure.
The single most notable thing is that while PT outputs trace data in a compressed binary format, it will still generate hundreds of megabytes of trace data per second per core. Decoding this binary stream takes 2-3 orders of magnitude the cpu time that it takes to generate it. These considerations make it impossible to carry out decoding in kernel space. Therefore, the trace data is exported to userspace as a zero-copy mapping that userspace can collect and store for later decoding. To address this, this patchset extends perf ring buffer with an "AUX space", which is allocated for hardware blocks such as PT to export their trace data with minimal overhead. This space can be configured via buffer's user page and mmapped from the same file descriptor with a given offset. Data can then be collected from it by reading the aux_head (write) pointer from the user page and updating aux_tail (read) pointer similarly to data_{head,tail} of the traditional perf buffer. There is an api between perf core and pmu drivers that wish to make use of this AUX space to export their data.
For tracing blocks that don't support hardware scatter-gather tables, we provide high-order physically contiguous allocations to minimize the overhead needed for software double buffering and PMI pressure.
This way we get a normal perf data stream that provides sideband information that is required to decode the trace data, such as MMAPs, COMMs etc, plus the actual trace in its own logical space.
If the trace buffer is mapped writable, the driver will stop tracing when it fills up (aux_head approaches aux_tail), till data is read, aux_tail pointer is moved forward and an ioctl() is issued to re-enable tracing. If the trace buffer is mapped read only, the tracing will continue, overwriting older data, so that the buffer always contains the most recent data. Tracing can be stopped with an ioctl() and restarted once the data is collected.
Another use case is annotating samples of other perf events: setting PERF_SAMPLE_AUX requests attr.aux_sample_size bytes of trace to be included in each event's sample.
This patchset consists of necessary changes to the perf kernel infrastructure, and PT and BTS pmu drivers. The tooling support is not included in this series, however, it can be found in my github tree [2].
This version changes the way watermarks are handled for AUX area and gets rid of the notion of "itrace" both in the core and in the perf interface (event attribute), which makes it more logical.
[1] http://software.intel.com/en-us/intel-isa-extensions [2] http://github.com/virtuoso/linux-perf/tree/intel_pt
Alexander Shishkin (21): perf: Add data_{offset,size} to user_page perf: Support high-order allocations for AUX space perf: Add a capability for AUX_NO_SG pmus to do software double buffering perf: Add a pmu capability for "exclusive" events perf: Redirect output from inherited events to parents perf: Add api for pmus to write to AUX space perf: Add AUX record perf: Support overwrite mode for AUX area perf: Add wakeup watermark control to AUX area perf: add ITRACE_START record to indicate that tracing has started x86: Add Intel Processor Trace (INTEL_PT) cpu feature detection x86: perf: Intel PT and LBR/BTS are mutually exclusive x86: perf: intel_pt: Intel PT PMU driver x86: perf: intel_bts: Add BTS PMU driver perf: Add rb_{alloc,free}_kernel api perf: Add a helper to copy AUX data in the kernel perf: Add a helper for looking up pmus by type perf: Add infrastructure for using AUX data in perf samples perf: Allocate ring buffers for inherited per-task kernel events perf: Allow AUX sampling for multiple events perf: Allow sampling of inherited events
Peter Zijlstra (1): perf: Add AUX area to ring buffer for raw data streams
arch/x86/include/asm/cpufeature.h | 1 + arch/x86/include/uapi/asm/msr-index.h | 18 + arch/x86/kernel/cpu/Makefile | 1 + arch/x86/kernel/cpu/intel_pt.h | 129 ++++ arch/x86/kernel/cpu/perf_event.h | 14 + arch/x86/kernel/cpu/perf_event_intel.c | 14 +- arch/x86/kernel/cpu/perf_event_intel_bts.c | 501 +++++++++++++++ arch/x86/kernel/cpu/perf_event_intel_ds.c | 11 +- arch/x86/kernel/cpu/perf_event_intel_lbr.c | 9 +- arch/x86/kernel/cpu/perf_event_intel_pt.c | 973 +++++++++++++++++++++++++++++ arch/x86/kernel/cpu/scattered.c | 1 + include/linux/perf_event.h | 56 +- include/uapi/linux/perf_event.h | 69 +- kernel/events/core.c | 545 +++++++++++++++- kernel/events/internal.h | 50 ++ kernel/events/ring_buffer.c | 310 ++++++++- 16 files changed, 2658 insertions(+), 44 deletions(-) create mode 100644 arch/x86/kernel/cpu/intel_pt.h create mode 100644 arch/x86/kernel/cpu/perf_event_intel_bts.c create mode 100644 arch/x86/kernel/cpu/perf_event_intel_pt.c
-- 2.1.0
| |