Re: [PATCH 1/2] lib: Add module for testing preemptoff/irqsoff latency tracers

On Tue, 10 Jul 2018 23:35:39 -0700 Joel Fernandes joel@joelfernandes.org wrote:

Co-developed-by: Erick Reyes erickreyes@google.com

A co-developer needs to add their signed off by. To specify that Erick is a co-author, you could do:

[ Erick is a co-developer of this commit ] Signed-off-by: Add Erick's SOB here.

Cc: Andy Shevchenko andriy.shevchenko@linux.intel.com Reviewed-by: Andy Shevchenko andriy.shevchenko@linux.intel.com Signed-off-by: Joel Fernandes (Google) joel@joelfernandes.org

---

kernel/trace/Kconfig | 15 ++++++ kernel/trace/Makefile | 1 + kernel/trace/preemptirq_delay_test.c | 72 ++++++++++++++++++++++++++++ 3 files changed, 88 insertions(+) create mode 100644 kernel/trace/preemptirq_delay_test.c

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig index 8d51351e3149..eb5ab6b511e2 100644 --- a/kernel/trace/Kconfig +++ b/kernel/trace/Kconfig @@ -699,6 +699,21 @@ config RING_BUFFER_STARTUP_TEST If unsure, say N +config PREEMPTIRQ_DELAY_TEST

• tristate "Preempt / IRQ disable delay thread to test latency tracers"
• depends on m
• help

•  Select this option to build a test module that can help test latency
  

•  tracers by executing a preempt or irq disable section with a user
  

•  configurable delay. The module busy waits for the duration of the
  

•  critical section.
  

•  For example, the following invocation forces a one-time irq-disabled
  

•  critical section for 500us:
  

•  modprobe preemptirq_delay_test test_mode=irq delay=500000
  

•  If unsure, say N
  

config TRACE_EVAL_MAP_FILE bool "Show eval mappings for trace events" depends on TRACING diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile index 84a0cb222f20..677540bb1b62 100644 --- a/kernel/trace/Makefile +++ b/kernel/trace/Makefile @@ -36,6 +36,7 @@ obj-$(CONFIG_TRACING_MAP) += tracing_map.o obj-$(CONFIG_CONTEXT_SWITCH_TRACER) += trace_sched_switch.o obj-$(CONFIG_FUNCTION_TRACER) += trace_functions.o obj-$(CONFIG_PREEMPTIRQ_TRACEPOINTS) += trace_preemptirq.o +obj-$(CONFIG_PREEMPTIRQ_DELAY_TEST) += preemptirq_delay_test.o obj-$(CONFIG_IRQSOFF_TRACER) += trace_irqsoff.o obj-$(CONFIG_PREEMPT_TRACER) += trace_irqsoff.o obj-$(CONFIG_SCHED_TRACER) += trace_sched_wakeup.o diff --git a/kernel/trace/preemptirq_delay_test.c b/kernel/trace/preemptirq_delay_test.c new file mode 100644 index 000000000000..c97a026c0720 --- /dev/null +++ b/kernel/trace/preemptirq_delay_test.c @@ -0,0 +1,72 @@ +// SPDX-License-Identifier: GPL-2.0 +/*

• • Preempt / IRQ disable delay thread to test latency tracers
• • Copyright (C) 2018 Joel Fernandes (Google) joel@joelfernandes.org
• */

+#include <linux/delay.h> +#include <linux/interrupt.h> +#include <linux/irq.h> +#include <linux/kernel.h> +#include <linux/kthread.h> +#include <linux/ktime.h> +#include <linux/module.h> +#include <linux/printk.h> +#include <linux/string.h>

+static ulong delay = 100; +static char test_mode[10] = "irq";

+module_param_named(delay, delay, ulong, S_IRUGO); +module_param_string(test_mode, test_mode, 10, S_IRUGO); +MODULE_PARM_DESC(delay, "Period in microseconds (100 uS default)"); +MODULE_PARM_DESC(test_mode, "Mode of the test such as preempt or irq (default irq)");

+static void busy_wait(ulong time) +{

• ktime_t start, end;
• start = ktime_get();
• do {

• end = ktime_get();
  

• if (kthread_should_stop())
  

• 	break;
  

• } while (ktime_to_ns(ktime_sub(end, start)) < (time * 1000));

+}

+int preemptirq_delay_run(void *data) +{

• unsigned long flags;
• if (!strcmp(test_mode, "irq")) {

• local_irq_save(flags);
  

• busy_wait(delay);
  

• local_irq_restore(flags);
  

• } else if (!strcmp(test_mode, "preempt")) {

• preempt_disable();
  

• busy_wait(delay);
  

• preempt_enable();
  

• }
• return 0;

+}

+static int __init preemptirq_delay_init(void) +{

• char task_name[50];
• struct task_struct *test_task;
• snprintf(task_name, sizeof(task_name), "%s_test", test_mode);
• test_task = kthread_run(preemptirq_delay_run, NULL, task_name);
• return PTR_ERR_OR_ZERO(test_task);

+}

+static void __exit preemptirq_delay_exit(void) +{

• return;

+}

+module_init(preemptirq_delay_init) +module_exit(preemptirq_delay_exit) +MODULE_LICENSE("GPL v2");

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