linux-kernel - [PATCH v4 0/3] *** Latency histograms

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Date:   Tue, 30 Aug 2016 15:58:41 +0530
From:   Binoy Jayan <binoy.jayan@...aro.org>
To:     "Steven Rostedt (Red Hat)" <rostedt@...dmis.org>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Daniel Wagner <daniel.wagner@...-carit.de>,
        Arnd Bergmann <arnd@...db.de>, linux-kernel@...r.kernel.org,
        Masami <masami.hiramatsu@...aro.org>,
        Binoy Jayan <binoy.jayan@...aro.org>
Subject: [PATCH v4 0/3] *** Latency histograms - IRQSOFF,PREEMPTOFF ***

Hi,

Thank you Daniel for reviewing v3 throroughly.
These set of patches [v4] capture latency events caused by interrupts and
premption disabled in kernel. The patches are based on the hist trigger
feature developed by Tom Zanussi.

v3: https://lkml.org/lkml/2016/8/29/50
v2: https://lkml.org/lkml/2016/8/24/296

Mount Debugfs

mount -t debugfs nodev /sys/kernel/debug

Examples of triggers:
echo 'hist:key=latency.log2:val=hitcount:sort=latency' > /sys/kernel/debug/tracing/events/latency/latency_preempt/trigger
echo 'hist:key=cpu,latency:val=hitcount:sort=latency if cpu==1' > /sys/kernel/debug/tracing/events/latency/latency_preempt/trigger
echo 'hist:key=ltype,cpu:val=latency:sort=ltype,cpu if ltype==0' > /sys/kernel/debug/tracing/events/latency/latency_preempt/trigger

Histogram output:
cat /sys/kernel/debug/tracing/events/latency/latency_preempt/hist

Changes from v3 as per comments from Daniel
  - A few coding style changes
  - Dropped the field 'cpu' from the event format fields.

TODO:
1. perf interface. Not sure if this is needed
2. Latency histograms - process wakeup latency

Binoy

Binoy Jayan (2):
  tracing: Add trace_irqsoff tracepoints
  tracing: Histogram for missed timer offsets

Daniel Wagner (1):
  tracing: Deference pointers without RCU checks

 include/linux/hrtimer.h             |  3 ++
 include/linux/rculist.h             | 36 +++++++++++++++++++++
 include/linux/tracepoint.h          |  4 +--
 include/trace/events/latency.h      | 64 +++++++++++++++++++++++++++++++++++++
 kernel/time/hrtimer.c               | 40 +++++++++++++++++++++++
 kernel/trace/trace_events_filter.c  |  4 +--
 kernel/trace/trace_events_trigger.c |  6 ++--
 kernel/trace/trace_irqsoff.c        | 42 ++++++++++++++++++++++++
 8 files changed, 192 insertions(+), 7 deletions(-)
 create mode 100644 include/trace/events/latency.h

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