Commit 7bb7d802 authored by Daniel Bristot de Oliveira's avatar Daniel Bristot de Oliveira Committed by Steven Rostedt (VMware)
Browse files

trace/hwlat: Switch disable_migrate to mode none 

When in the round-robin mode, if the tracer detects a change in the
hwlatd thread affinity by an external tool, e.g., taskset, the
round-robin logic is disabled. The disable_migrate variable currently
tracks this.

With the addition of the "mode" config and the mode "none," the
disable_migrate logic is equivalent to switch to the "none" mode.

Hence, instead of using a hidden variable to track this behavior,
switch the mode to none, informing the user about this change.

Link: https://lkml.kernel.org/r/a679af672458d6b1f62252605905c5214030f247.1624372313.git.bristot@redhat.com



Cc: Phil Auld <pauld@redhat.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Kate Carcia <kcarcia@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Alexandre Chartre <alexandre.chartre@oracle.com>
Cc: Clark Willaims <williams@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: default avatarDaniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent 8fa826b7

kernel/trace/trace_hwlat.c

+5 −8
Original line number Diff line number Diff line
@@ -286,7 +286,6 @@ static int get_sample(void) 
}



static struct cpumask save_cpumask;

static bool disable_migrate;



static void move_to_next_cpu(void)

{
@@ -294,15 +293,13 @@ static void move_to_next_cpu(void) 
	struct trace_array *tr = hwlat_trace;

	int next_cpu;



	if (disable_migrate)

		return;

	/*

	 * If for some reason the user modifies the CPU affinity

	 * of this thread, then stop migrating for the duration

	 * of the current test.

	 */

	if (!cpumask_equal(current_mask, current->cpus_ptr))

		goto disable;

		goto change_mode;



	get_online_cpus();

	cpumask_and(current_mask, cpu_online_mask, tr->tracing_cpumask);
@@ -313,7 +310,7 @@ static void move_to_next_cpu(void) 
		next_cpu = cpumask_first(current_mask);



	if (next_cpu >= nr_cpu_ids) /* Shouldn't happen! */

		goto disable;

		goto change_mode;



	cpumask_clear(current_mask);

	cpumask_set_cpu(next_cpu, current_mask);
@@ -321,8 +318,9 @@ static void move_to_next_cpu(void) 
	sched_setaffinity(0, current_mask);

	return;



 disable:

	disable_migrate = true;

 change_mode:

	hwlat_data.thread_mode = MODE_NONE;

	pr_info(BANNER "cpumask changed while in round-robin mode, switching to mode none\n");

}



/*
@@ -744,7 +742,6 @@ static int hwlat_tracer_init(struct trace_array *tr) 


	hwlat_trace = tr;



	disable_migrate = false;

	hwlat_data.count = 0;

	tr->max_latency = 0;

	save_tracing_thresh = tracing_thresh;