[PATCH v2 0/4] Some new features for the preempt/irqsoff tracers

[Viktor Rosendahl]

Hello all,

Changes in v2:
- I have tried to improve some of the commit messages by adding
  additional explanations.
- [PATCH 2/4]: We use burst size checking instead of the confusing
  modulo game. The example given in the Kconfig file is corrected and
  extended. I was not able to find a way to use the module parameters
  as trigger, so I have left the sysfs trigger file as is.


This series is meant to address two issues with the latency tracing.

The first three patches provide a method to trace latencies that
always occurs very close to each other and to differentiate between
them, in spite of the fact that the latency tracers always work in
overwrite mode.

[PATCH 1/4] This implement fs notification for preempt/irqsoff. It
makes it possible for userspace to detect when a new latency has
been detected.

[PATCH 2/4] This extends the preemptirq_delay_test module so that
it can be used to generate a burst of closely occurring latencies.

[PATCH 3/4] This adds a user space program to the tools directory
that utilizes the fs notification feature and a randomized algorithm
to print out any of the latencies in a burst with approximately equal
probability.

The last patch is not directly connected but doesn't apply cleanly on
its own:

[PATCH 4/4] This adds the option CONFIG_TRACE_CONSOLE_LATENCY to
decide whether we want to trace prints to the console or not.

best regards,

Viktor Rosendahl

Viktor Rosendahl (4):
  ftrace: Implement fs notification for preempt/irqsoff tracers
  preemptirq_delay_test: Add the burst feature and a sysfs trigger
  Add the latency-collector to tools
  ftrace: Add an option for tracing console latencies

 include/linux/irqflags.h             |   13 +
 kernel/printk/printk.c               |    5 +-
 kernel/trace/Kconfig                 |   27 +-
 kernel/trace/preemptirq_delay_test.c |  145 +++-
 kernel/trace/trace.c                 |   31 +-
 kernel/trace/trace.h                 |    5 +
 kernel/trace/trace_irqsoff.c         |   35 +
 tools/Makefile                       |   14 +-
 tools/trace/Makefile                 |   20 +
 tools/trace/latency-collector.c      | 1190 ++++++++++++++++++++++++++
 10 files changed, 1453 insertions(+), 32 deletions(-)
 create mode 100644 tools/trace/Makefile
 create mode 100644 tools/trace/latency-collector.c

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2.17.1