linux-stable.git/tools/perf/util/session.c, branch v6.0

perf tools: Support reading PERF_FORMAT_LOST

2022-08-19T18:56:56+00:00

The recent kernel added lost count can be read from either read(2) or
ring buffer data with PERF_SAMPLE_READ.  As it's a variable length data
we need to access it according to the format info.

But for perf tools use cases, PERF_FORMAT_ID is always set.  So we can
only check PERF_FORMAT_LOST bit to determine the data format.

Add sample_read_value_size() and next_sample_read_value() helpers to
make it a bit easier to access.  Use them in all places where it reads
the struct sample_read_value.

Signed-off-by: Namhyung Kim 
Acked-by: Jiri Olsa 
Cc: Ian Rogers 
Cc: Ingo Molnar 
Cc: Peter Zijlstra 
Link: https://lore.kernel.org/r/20220819003644.508916-5-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo

perf cpumap: Fix alignment for masks in event encoding

2022-08-19T18:30:28+00:00

A mask encoding of a cpu map is laid out as:

  u16 nr
  u16 long_size
  unsigned long mask[];

However, the mask may be 8-byte aligned meaning there is a 4-byte pad
after long_size. This means 32-bit and 64-bit builds see the mask as
being at different offsets. On top of this the structure is in the byte
data[] encoded as:

  u16 type
  char data[]

This means the mask's struct isn't the required 4 or 8 byte aligned, but
is offset by 2. Consequently the long reads and writes are causing
undefined behavior as the alignment is broken.

Fix the mask struct by creating explicit 32 and 64-bit variants, use a
union to avoid data[] and casts; the struct must be packed so the
layout matches the existing perf.data layout. Taking an address of a
member of a packed struct breaks alignment so pass the packed
perf_record_cpu_map_data to functions, so they can access variables with
the right alignment.

As the 64-bit version has 4 bytes of padding, optimizing writing to only
write the 32-bit version.

Committer notes:

Disable warnings about 'packed' that break the build in some arches like
riscv64, but just around that specific struct.

Signed-off-by: Ian Rogers 
Acked-by: Jiri Olsa 
Cc: Adrian Hunter 
Cc: Alexander Shishkin 
Cc: Alexey Bayduraev 
Cc: Athira Jajeev 
Cc: Colin Ian King 
Cc: Dave Marchevsky 
Cc: German Gomez 
Cc: Gustavo A. R. Silva 
Cc: Ingo Molnar 
Cc: James Clark 
Cc: Kees Kook 
Cc: Leo Yan 
Cc: Mark Rutland 
Cc: Namhyung Kim 
Cc: Peter Zijlstra 
Cc: Riccardo Mancini 
Cc: Song Liu 
Cc: Stephane Eranian 
Link: https://lore.kernel.org/r/20220614143353.1559597-5-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo

perf tools: Automatically use guest kcore_dir if present

2022-07-20T14:08:37+00:00

When registering a guest machine using machine_pid from the id index,
check perf.data for a matching kcore_dir subdirectory and set the
kallsyms file name accordingly. If set, use it to find the machine's
kernel symbols and object code (from kcore).

Signed-off-by: Adrian Hunter 
Cc: Andi Kleen 
Cc: Ian Rogers 
Cc: Jiri Olsa 
Cc: Namhyung Kim 
Cc: kvm@vger.kernel.org
Link: https://lore.kernel.org/r/20220711093218.10967-23-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo

perf auxtrace: Add machine_pid and vcpu to auxtrace_error

2022-07-20T14:08:17+00:00

Add machine_pid and vcpu to struct perf_record_auxtrace_error. The existing
fmt member is used to identify the new format.

The new members make it possible to easily differentiate errors from guest
machines.

Signed-off-by: Adrian Hunter 
Acked-by: Ian Rogers 
Cc: Andi Kleen 
Cc: Jiri Olsa 
Cc: Namhyung Kim 
Cc: kvm@vger.kernel.org
Link: https://lore.kernel.org/r/20220711093218.10967-18-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo

perf session: Use sample->machine_pid to find guest machine

2022-07-20T14:08:08+00:00

If machine_pid is set, use it to find the guest machine.

Signed-off-by: Adrian Hunter 
Acked-by: Ian Rogers 
Cc: Andi Kleen 
Cc: Jiri Olsa 
Cc: Namhyung Kim 
Cc: kvm@vger.kernel.org
Link: https://lore.kernel.org/r/20220711093218.10967-15-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo

perf tools: Add guest_cpu to hypervisor threads

2022-07-20T14:08:04+00:00

It is possible to know which guest machine was running at a point in time
based on the PID of the currently running host thread. That is, perf
identifies guest machines by the PID of the hypervisor.

To determine the guest CPU, put it on the hypervisor (QEMU) thread for
that VCPU.

This is done when processing the id_index which provides the necessary
information.

Signed-off-by: Adrian Hunter 
Cc: Andi Kleen 
Cc: Ian Rogers 
Cc: Jiri Olsa 
Cc: Namhyung Kim 
Cc: kvm@vger.kernel.org
Link: https://lore.kernel.org/r/20220711093218.10967-13-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo

perf session: Create guest machines from id_index

2022-07-20T14:07:58+00:00

Now that id_index has machine_pid, use it to create guest machines.
Create the guest machines with an idle thread because guest events
for "swapper" will be possible.

Signed-off-by: Adrian Hunter 
Acked-by: Ian Rogers 
Cc: Andi Kleen 
Cc: Jiri Olsa 
Cc: Namhyung Kim 
Cc: kvm@vger.kernel.org
Link: https://lore.kernel.org/r/20220711093218.10967-12-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo

perf tools: Add machine_pid and vcpu to id_index

2022-07-20T14:07:58+00:00

When injecting events from a guest perf.data file, the events will have
separate sample ID numbers. These ID numbers can then be used to determine
which machine an event belongs to. To facilitate that, add machine_pid and
vcpu to id_index records. For backward compatibility, these are added at
the end of the record, and the length of the record is used to determine
if they are present or not.

Note, this is needed because the events from a guest perf.data file contain
the pid/tid of the process running at that time inside the VM not the
pid/tid of the (QEMU) hypervisor thread. So a way is needed to relate
guest events back to the guest machine and VCPU, and using sample ID
numbers for that is relatively simple and convenient.

Signed-off-by: Adrian Hunter 
Cc: Andi Kleen 
Cc: Ian Rogers 
Cc: Jiri Olsa 
Cc: Namhyung Kim 
Cc: kvm@vger.kernel.org
Link: https://lore.kernel.org/r/20220711093218.10967-11-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo

perf tools: Export perf_event__process_finished_round()

2022-07-20T14:07:37+00:00

Export perf_event__process_finished_round() so it can be used elsewhere.

This is needed in perf inject to obey finished-round ordering.

Signed-off-by: Adrian Hunter 
Acked-by: Ian Rogers 
Cc: Jiri Olsa 
Cc: Namhyung Kim 
Cc: kvm@vger.kernel.org
Link: https://lore.kernel.org/r/20220711093218.10967-5-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo

perf record: Add finished init event

2022-06-23T14:54:22+00:00

In preparation for recording sideband events in a virtual machine guest so
that they can be injected into a host perf.data file.

This is needed to enable injecting events after the initial synthesized
user events (that have an all zero id sample) but before regular events.

Committer notes:

Add entry about PERF_RECORD_FINISHED_INIT to
tools/perf/Documentation/perf.data-file-format.txt.

Committer testing:

Before:

  # perf report -D | grep FINISHED
  0 0x5910 [0x8]: PERF_RECORD_FINISHED_ROUND
    FINISHED_ROUND events:          1  ( 0.5%)
  #

After:

  # perf record -- sleep 1
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 0.020 MB perf.data (7 samples) ]
  # perf report -D | grep FINISHED
  0 0x5068 [0x8]: PERF_RECORD_FINISHED_INIT: unhandled!
  0 0x5390 [0x8]: PERF_RECORD_FINISHED_ROUND
    FINISHED_ROUND events:          1  ( 0.5%)
     FINISHED_INIT events:          1  ( 0.5%)
  #

Signed-off-by: Adrian Hunter 
Acked-by: Ian Rogers 
Tested-by: Arnaldo Carvalho de Melo 
Cc: Jiri Olsa 
Cc: Namhyung Kim 
Link: https://lore.kernel.org/r/20220610113316.6682-5-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo