[PATCH v4 0/4] Some new features for the latency tracers

[Viktor Rosendahl <viktor.rosendahl@gmail.com>]

Hello all,

Changes in v4:

- [PATCH 1/4]:
  * Improved support for multiple active trace instances by storing entries
    that cannot be notified immediately in a linked list instead of a
    single pointer. With multiple instances this could happen.

  * Register trace_maxlat_fsnotify_init() with late_initcall_sync().
    Previously it was piggy backed on tracer_init_tracefs() and it got
    called more than once.

  * Added some comments.

- [PATCH 3/4]:
  * Some of the code was incorrectly added in the next patch. Improved
    commit message.

- [PATCH 4/4]:
  * Some code from the previous patch was incorrectly included here.


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 work in overwrite mode.

[PATCH 1/4] This implement fs notification for tracing_max_latency. 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 console-latency to the trace options. This
makes it possible to enable tracing of console latencies.

best regards,

Viktor

Viktor Rosendahl (4):
  ftrace: Implement fs notification for tracing_max_latency
  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             |   21 +
 include/trace/events/power.h         |   40 +
 include/trace/events/sched.h         |   40 +
 kernel/printk/printk.c               |    6 +-
 kernel/sched/core.c                  |    2 +
 kernel/sched/idle.c                  |    2 +
 kernel/trace/Kconfig                 |    6 +-
 kernel/trace/preemptirq_delay_test.c |  145 ++-
 kernel/trace/trace.c                 |  168 +++-
 kernel/trace/trace.h                 |   13 +
 kernel/trace/trace_hwlat.c           |    4 +-
 kernel/trace/trace_irqsoff.c         |   12 +
 tools/Makefile                       |   14 +-
 tools/trace/Makefile                 |   20 +
 tools/trace/latency-collector.c      | 1211 ++++++++++++++++++++++++++
 15 files changed, 1671 insertions(+), 33 deletions(-)
 create mode 100644 tools/trace/Makefile
 create mode 100644 tools/trace/latency-collector.c

-- 
2.17.1