[lttng-dev] [PATCH lttng-modules] Add preemptirq instrumentation

Tue Dec 19 21:15:15 UTC 2017

On 2017-12-19 16:10, Michael Jeanson wrote:
> The tracepoints were introduced in kernl 4.15 alongside the config
> option PREEMPTIRQ_EVENTS.
> 
> This enables tracing of disable and enable events for preemption and
> irqs. For tracing preempt disable/enable events, DEBUG_PREEMPT must be
> enabled. For tracing irq disable/enable events, PROVE_LOCKING must
> be disabled.
> 
> See upstream commit:
> 
>   commit d59158162e032917a428704160a2063a02405ec6
>   Author: Joel Fernandes <joelaf at google.com>
>   Date:   Tue Oct 10 15:51:37 2017 -0700
> 
>     tracing: Add support for preempt and irq enable/disable events
> 
>     Preempt and irq trace events can be used for tracing the start and
>     end of an atomic section which can be used by a trace viewer like
>     systrace to graphically view the start and end of an atomic section and
>     correlate them with latencies and scheduling issues.
> 
>     This also serves as a prelude to using synthetic events or probes to
>     rewrite the preempt and irqsoff tracers, along with numerous benefits of
>     using trace events features for these events.
>     Link: http://lkml.kernel.org/r/20171006005432.14244-3-joelaf@google.com
>     Link: http://lkml.kernel.org/r/20171010225137.17370-1-joelaf@google.com
> 
> Signed-off-by: Michael Jeanson <mjeanson at efficios.com>
> ---
>  instrumentation/events/lttng-module/preemptirq.h | 72 ++++++++++++++++++++++++
>  probes/Kbuild                                    |  4 ++
>  probes/lttng-probe-preemptirq.c                  | 49 ++++++++++++++++
>  3 files changed, 125 insertions(+)
>  create mode 100644 instrumentation/events/lttng-module/preemptirq.h
>  create mode 100644 probes/lttng-probe-preemptirq.c
> 
> diff --git a/instrumentation/events/lttng-module/preemptirq.h b/instrumentation/events/lttng-module/preemptirq.h
> new file mode 100644
> index 0000000..55f7aaa
> --- /dev/null
> +++ b/instrumentation/events/lttng-module/preemptirq.h
> @@ -0,0 +1,72 @@
> +#ifdef CONFIG_PREEMPTIRQ_EVENTS
> +
> +#undef TRACE_SYSTEM
> +#define TRACE_SYSTEM preemptirq
> +
> +#if !defined(LTTNG_TRACE_PREEMPTIRQ_H) || defined(TRACE_HEADER_MULTI_READ)
> +#define LTTNG_TRACE_PREEMPTIRQ_H
> +
> +#include <linux/ktime.h>
> +#include <linux/string.h>
> +#include <asm/sections.h>
> +#include <probes/lttng-tracepoint-event.h>
> +
> +
> +LTTNG_TRACEPOINT_EVENT_CLASS(preemptirq_template,
> +
> +	TP_PROTO(unsigned long ip, unsigned long parent_ip),
> +
> +	TP_ARGS(ip, parent_ip),
> +
> +	TP_FIELDS(
> +		ctf_integer(unsigned long, caller, ip)
> +		ctf_integer(unsigned long, parent, parent_ip)
> +	)
> +)
> +
> +#ifndef CONFIG_PROVE_LOCKING
> +LTTNG_TRACEPOINT_EVENT_INSTANCE_MAP(preemptirq_template, irq_disable,
> +
> +	preemptirq_irq_disable,
> +
> +	TP_PROTO(unsigned long ip, unsigned long parent_ip),
> +
> +	TP_ARGS(ip, parent_ip)
> +)
> +
> +LTTNG_TRACEPOINT_EVENT_INSTANCE_MAP(preemptirq_template, irq_enable,
> +
> +	preemptirq_irq_enable,
> +
> +	TP_PROTO(unsigned long ip, unsigned long parent_ip),
> +
> +	TP_ARGS(ip, parent_ip)
> +)
> +#endif /* !CONFIG_PROVE_LOCKING */
> +
> +#ifdef CONFIG_DEBUG_PREEMPT
> +LTTNG_TRACEPOINT_EVENT_INSTANCE_MAP(preemptirq_template, preempt_disable,
> +
> +	preemptirq_preempt_disable,
> +
> +	TP_PROTO(unsigned long ip, unsigned long parent_ip),
> +
> +	TP_ARGS(ip, parent_ip)
> +)
> +
> +LTTNG_TRACEPOINT_EVENT_INSTANCE_MAP(preemptirq_template, preempt_enable,
> +
> +	preemptirq_preempt_enable,
> +
> +	TP_PROTO(unsigned long ip, unsigned long parent_ip),
> +
> +	TP_ARGS(ip, parent_ip)
> +)
> +#endif /* CONFIG_DEBUG_PREEMPT */
> +
> +#endif /* LTTNG_TRACE_PREEMPTIRQ_H */
> +
> +/* This part must be outside protection */
> +#include <probes/define_trace.h>
> +
> +#endif /* CONFIG_PREEMPTIRQ_EVENTS */
> diff --git a/probes/Kbuild b/probes/Kbuild
> index 70a3d86..ff9c5f5 100644
> --- a/probes/Kbuild
> +++ b/probes/Kbuild
> @@ -266,4 +266,8 @@ ifneq ($(CONFIG_DYNAMIC_FTRACE),)
>    endif
>  endif # CONFIG_DYNAMIC_FTRACE
>  
> +ifneq ($(CONFIG_PREEMPTIRQ_EVENTS),)
> +  obj-$(CONFIG_LTTNG) += lttng-probe-preemptirq.o
> +endif # CONFIG_PREEMPTIRQ_EVENTS
> +
>  # vim:syntax=make
> diff --git a/probes/lttng-probe-preemptirq.c b/probes/lttng-probe-preemptirq.c
> new file mode 100644
> index 0000000..1270771
> --- /dev/null
> +++ b/probes/lttng-probe-preemptirq.c
> @@ -0,0 +1,49 @@
> +/*
> + * probes/lttng-probe-preemptirq.c
> + *
> + * LTTng preemptirq probes.
> + *
> + * Copyright (C) 2010-2012 Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
> + *               2017 Michael Jeanson <mjeanson at efficios.com>
> + *
> + * This library is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; only
> + * version 2.1 of the License.
> + *
> + * This library is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with this library; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
> + */
> +
> +#include <linux/module.h>
> +#include <linux/uaccess.h>
> +#include <lttng-tracer.h>
> +
> +/*
> + * Create the tracepoint static inlines from the kernel to validate that our
> + * trace event macros match the kernel we run on.
> + */
> +#include <trace/events/preemptirq.h>
> +
> +/*
> + * Create LTTng tracepoint probes.
> + */
> +#define LTTNG_PACKAGE_BUILD
> +#define CREATE_TRACE_POINTS
> +#define TRACE_INCLUDE_PATH instrumentation/events/lttng-module
> +
> +#include <instrumentation/events/lttng-module/preemptirq.h>
> +
> +MODULE_LICENSE("GPL and additional rights");
> +MODULE_AUTHOR("Michael Jeanson <mjeanson at efficios.com>");
> +MODULE_DESCRIPTION("LTTng preemptirq probes");
> +MODULE_VERSION(__stringify(LTTNG_MODULES_MAJOR_VERSION) "."
> +	__stringify(LTTNG_MODULES_MINOR_VERSION) "."
> +	__stringify(LTTNG_MODULES_PATCHLEVEL_VERSION)
> +	LTTNG_MODULES_EXTRAVERSION);
> 

This patch should of been submitted as an RFC.