linux-toradex.git/kernel/events/ring_buffer.c, branch v5.1-rc3

perf/ring_buffer: Use high order allocations for AUX buffers optimistically

2019-03-09T13:10:30+00:00

Currently, the AUX buffer allocator will use high-order allocations
for PMUs that don't support hardware scatter-gather chaining to ensure
large contiguous blocks of pages, and always use an array of single
pages otherwise.

There is, however, a tangible performance benefit in using larger chunks
of contiguous memory even in the latter case, that comes from not having
to fetch the next page's address at every page boundary. In particular,
a task running under Intel PT on an Atom CPU shows 1.5%-2% less runtime
penalty with a single multi-page output region in snapshot mode (no PMI)
than with multiple single-page output regions, from ~6% down to ~4%. For
the snapshot mode it does make a difference as it is intended to run over
long periods of time.

For this reason, change the allocation policy to always optimistically
start with the highest possible order when allocating pages for the AUX
buffer, desceding until the allocation succeeds or order zero allocation
fails.

Signed-off-by: Alexander Shishkin 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Andy Lutomirski 
Cc: Arnaldo Carvalho de Melo 
Cc: Borislav Petkov 
Cc: Dave Hansen 
Cc: H. Peter Anvin 
Cc: Jiri Olsa 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Rik van Riel 
Cc: Stephane Eranian 
Cc: Thomas Gleixner 
Cc: Vince Weaver 
Link: https://lkml.kernel.org/r/20190215114727.62648-2-alexander.shishkin@linux.intel.com
Signed-off-by: Ingo Molnar

Merge branch 'linus' into perf/core, to pick up fixes

2019-02-28T07:27:17+00:00

Signed-off-by: Ingo Molnar

perf/core: Fix impossible ring-buffer sizes warning

2019-02-13T07:05:02+00:00

The following commit:

  9dff0aa95a32 ("perf/core: Don't WARN() for impossible ring-buffer sizes")

results in perf recording failures with larger mmap areas:

  root@skl:/tmp# perf record -g -a
  failed to mmap with 12 (Cannot allocate memory)

The root cause is that the following condition is buggy:

	if (order_base_2(size) >= MAX_ORDER)
		goto fail;

The problem is that @size is in bytes and MAX_ORDER is in pages,
so the right test is:

	if (order_base_2(size) >= PAGE_SHIFT+MAX_ORDER)
		goto fail;

Fix it.

Reported-by: "Jin, Yao" 
Bisected-by: Borislav Petkov 
Analyzed-by: Peter Zijlstra 
Cc: Julien Thierry 
Cc: Mark Rutland 
Cc: Alexander Shishkin 
Cc: Arnaldo Carvalho de Melo 
Cc: Jiri Olsa 
Cc: Linus Torvalds 
Cc: Namhyung Kim 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Greg Kroah-Hartman 
Cc: 
Fixes: 9dff0aa95a32 ("perf/core: Don't WARN() for impossible ring-buffer sizes")
Signed-off-by: Ingo Molnar

perf/aux: Make perf_event accessible to setup_aux()

2019-02-06T13:00:39+00:00

When pmu::setup_aux() is called the coresight PMU needs to know which
sink to use for the session by looking up the information in the
event's attr::config2 field.

As such simply replace the cpu information by the complete perf_event
structure and change all affected customers.

Signed-off-by: Mathieu Poirier 
Reviewed-by: Suzuki Poulouse 
Acked-by: Peter Zijlstra 
Cc: Adrian Hunter 
Cc: Alexander Shishkin 
Cc: Alexei Starovoitov 
Cc: Greg Kroah-Hartman 
Cc: H. Peter Anvin 
Cc: Heiko Carstens 
Cc: Jiri Olsa 
Cc: Mark Rutland 
Cc: Martin Schwidefsky 
Cc: Namhyung Kim 
Cc: Thomas Gleixner 
Cc: Will Deacon 
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-s390@vger.kernel.org
Link: http://lkml.kernel.org/r/20190131184714.20388-2-mathieu.poirier@linaro.org
Signed-off-by: Arnaldo Carvalho de Melo

perf/ring_buffer: Convert ring_buffer.aux_refcount to refcount_t

2019-02-04T07:46:17+00:00

atomic_t variables are currently used to implement reference
counters with the following properties:

 - counter is initialized to 1 using atomic_set()
 - a resource is freed upon counter reaching zero
 - once counter reaches zero, its further
   increments aren't allowed
 - counter schema uses basic atomic operations
   (set, inc, inc_not_zero, dec_and_test, etc.)

Such atomic variables should be converted to a newly provided
refcount_t type and API that prevents accidental counter overflows
and underflows. This is important since overflows and underflows
can lead to use-after-free situation and be exploitable.

The variable ring_buffer.aux_refcount is used as pure reference counter.
Convert it to refcount_t and fix up the operations.

** Important note for maintainers:

Some functions from refcount_t API defined in lib/refcount.c
have different memory ordering guarantees than their atomic
counterparts. Please check Documentation/core-api/refcount-vs-atomic.rst
for more information.

Normally the differences should not matter since refcount_t provides
enough guarantees to satisfy the refcounting use cases, but in
some rare cases it might matter.
Please double check that you don't have some undocumented
memory guarantees for this variable usage.

For the ring_buffer.aux_refcount it might make a difference
in following places:

 - perf_aux_output_begin(): increment in refcount_inc_not_zero() only
   guarantees control dependency on success vs. fully ordered
   atomic counterpart
 - rb_free_aux(): decrement in refcount_dec_and_test() only
   provides RELEASE ordering and ACQUIRE ordering + control dependency
   on success vs. fully ordered atomic counterpart

Suggested-by: Kees Cook 
Signed-off-by: Elena Reshetova 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: David Windsor 
Reviewed-by: Hans Liljestrand 
Cc: Alexander Shishkin 
Cc: Arnaldo Carvalho de Melo 
Cc: Jiri Olsa 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: acme@kernel.org
Cc: namhyung@kernel.org
Link: https://lkml.kernel.org/r/1548678448-24458-4-git-send-email-elena.reshetova@intel.com
Signed-off-by: Ingo Molnar

perf/ring_buffer: Convert ring_buffer.refcount to refcount_t

2019-02-04T07:46:16+00:00

atomic_t variables are currently used to implement reference
counters with the following properties:

 - counter is initialized to 1 using atomic_set()
 - a resource is freed upon counter reaching zero
 - once counter reaches zero, its further
   increments aren't allowed
 - counter schema uses basic atomic operations
   (set, inc, inc_not_zero, dec_and_test, etc.)

Such atomic variables should be converted to a newly provided
refcount_t type and API that prevents accidental counter overflows
and underflows. This is important since overflows and underflows
can lead to use-after-free situation and be exploitable.

The variable ring_buffer.refcount is used as pure reference counter.
Convert it to refcount_t and fix up the operations.

** Important note for maintainers:

Some functions from refcount_t API defined in lib/refcount.c
have different memory ordering guarantees than their atomic
counterparts. Please check Documentation/core-api/refcount-vs-atomic.rst
for more information.

Normally the differences should not matter since refcount_t provides
enough guarantees to satisfy the refcounting use cases, but in
some rare cases it might matter.
Please double check that you don't have some undocumented
memory guarantees for this variable usage.

For the ring_buffer.refcount it might make a difference
in following places:

 - ring_buffer_get(): increment in refcount_inc_not_zero() only
   guarantees control dependency on success vs. fully ordered
   atomic counterpart
 - ring_buffer_put(): decrement in refcount_dec_and_test() only
   provides RELEASE ordering and ACQUIRE ordering + control dependency
   on success vs. fully ordered atomic counterpart

Suggested-by: Kees Cook 
Signed-off-by: Elena Reshetova 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: David Windsor 
Reviewed-by: Hans Liljestrand 
Cc: Alexander Shishkin 
Cc: Arnaldo Carvalho de Melo 
Cc: Jiri Olsa 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: acme@kernel.org
Cc: namhyung@kernel.org
Link: https://lkml.kernel.org/r/1548678448-24458-3-git-send-email-elena.reshetova@intel.com
Signed-off-by: Ingo Molnar

perf/core: Convert to SPDX license identifiers

2019-02-04T07:46:11+00:00

Use proper SPDX license identifiers instead of the bogus reference to
kernel-base/COPYING.

Signed-off-by: Thomas Gleixner 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Alexander Shishkin 
Cc: Arnaldo Carvalho de Melo 
Cc: Greg Kroah-Hartman 
Cc: Jiri Olsa 
Cc: Kate Stewart 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Link: https://lkml.kernel.org/r/20190116111308.012666937@linutronix.de
Signed-off-by: Ingo Molnar

perf/core: Don't WARN() for impossible ring-buffer sizes

2019-02-04T07:45:25+00:00

The perf tool uses /proc/sys/kernel/perf_event_mlock_kb to determine how
large its ringbuffer mmap should be. This can be configured to arbitrary
values, which can be larger than the maximum possible allocation from
kmalloc.

When this is configured to a suitably large value (e.g. thanks to the
perf fuzzer), attempting to use perf record triggers a WARN_ON_ONCE() in
__alloc_pages_nodemask():

   WARNING: CPU: 2 PID: 5666 at mm/page_alloc.c:4511 __alloc_pages_nodemask+0x3f8/0xbc8

Let's avoid this by checking that the requested allocation is possible
before calling kzalloc.

Reported-by: Julien Thierry 
Signed-off-by: Mark Rutland 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Julien Thierry 
Cc: Alexander Shishkin 
Cc: Arnaldo Carvalho de Melo 
Cc: Jiri Olsa 
Cc: Linus Torvalds 
Cc: Namhyung Kim 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: 
Link: https://lkml.kernel.org/r/20190110142745.25495-1-mark.rutland@arm.com
Signed-off-by: Ingo Molnar

perf: Suppress AUX/OVERWRITE records

2018-09-18T20:21:13+00:00

It has been pointed out to me many times that it is useful to be able to
switch off AUX records to save the bandwidth for records that actually
matter, for example, in AUX overwrite mode.

The usefulness of PERF_RECORD_AUX is in some of its flags, like the
TRUNCATED flag that tells the decoder where exactly gaps in the trace
are.  The OVERWRITE flag, on the other hand will be set on every single
record in overwrite mode. However, a PERF_RECORD_AUX[flags=OVERWRITE] is
generated on every target task's sched_out, which over time adds up to a
lot of useless information.

If any folks out there have userspace that depends on a constant stream
of OVERWRITE records for a good reason, they'll have to let us know.

Signed-off-by: Alexander Shishkin 
Acked-by: Ingo Molnar 
Acked-by: Peter Zijlstra 
Acked-by: Will Deacon 
Cc: Adrian Hunter 
Cc: Markus T Metzger 
Link: http://lkml.kernel.org/r/20180404145323.28651-1-alexander.shishkin@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo

Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2018-06-24T12:29:15+00:00

Pull perf fixes from Thomas Gleixner:
 "A pile of perf updates:

  Kernel side:

   - Remove an incorrect warning in uprobe_init_insn() when
     insn_get_length() fails. The error return code is handled at the
     call site.

   - Move the inline keyword to the right place in the perf ringbuffer
     code to address a W=1 build warning.

  Tooling:

  perf stat:

   - Fix metric column header display alignment

   - Improve error messages for default attributes, providing better
     output for error in command line.

   - Add --interval-clear option, to provide a 'watch' like printing

  perf script:

   - Show hw-cache events too

  perf c2c:

   - Fix data dependency problem in layout of 'struct c2c_hist_entry'

  Core:

   - Do not blindly assume that 'struct perf_evsel' can be obtained via
     a straight forward container_of() as there are call sites which
     hand in a plain 'struct hist' which is not part of a container.

   - Fix error index in the PMU event parser, so that error messages can
     point to the problematic token"

* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf/core: Move the inline keyword at the beginning of the function declaration
  uprobes/x86: Remove incorrect WARN_ON() in uprobe_init_insn()
  perf script: Show hw-cache events
  perf c2c: Keep struct hist_entry at the end of struct c2c_hist_entry
  perf stat: Add event parsing error handling to add_default_attributes
  perf stat: Allow to specify specific metric column len
  perf stat: Fix metric column header display alignment
  perf stat: Use only color_fprintf call in print_metric_only
  perf stat: Add --interval-clear option
  perf tools: Fix error index for pmu event parser
  perf hists: Reimplement hists__has_callchains()
  perf hists browser gtk: Use hist_entry__has_callchains()
  perf hists: Make hist_entry__has_callchains() work with 'perf c2c'
  perf hists: Save the callchain_size in struct hist_entry