linux-kernel - [PATCH 0/2] ring-buffer: More precise timestamps for nested writes

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Date:	Mon, 13 Apr 2015 21:29:11 -0500
From:	"Suresh E. Warrier" <warrier@...ux.vnet.ibm.com>
To:	lklml <linux-kernel@...r.kernel.org>
CC:	Steven Rostedt <rostedt@...dmis.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.com>,
	Paul Mackerras <paulus@...ba.org>
Subject: [PATCH 0/2] ring-buffer: More precise timestamps for nested writes

This patch set provides supports a way to record precise timestamps
for nested writes and a tunable to enable the behavior.

Nested writes occur when a trace writer is preempted, usually through
an interrupt and the interrupt handler also writes its own trace. It has
been noticed on large systems with lots of interrupts, several hundred
trace events can be recorded with the same time stamp.

Fixing this requires a small critical section in the trace write code
in which interrupts are disabled. This is an expensive operation for many
architectures. Hence, the need for a kernel tunable that allows the
feature to be enabled by admins only when needed.

Suresh Warrier (2):
  ring-buffer: Introduce precise nested timestamp sysfs attribute
  ring-buffer: More precise timestamps for nested writes

 Documentation/trace/ftrace.txt |  8 ++++
 include/linux/ring_buffer.h    |  9 +++++
 kernel/trace/ring_buffer.c     | 85 ++++++++++++++++++++++++++++++++++++++++--
 kernel/trace/trace.c           | 51 +++++++++++++++++++++++++
 4 files changed, 149 insertions(+), 4 deletions(-)

-- 
1.8.3.4

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