[PATCH v1 3/3] drivers/tty: increase priority for tty_buffer_worker

From: Oleksij Rempel
Date: Thu Jan 10 2019 - 05:12:41 EST


sched_priority = 1 is enough to dramatically reduce latency
on have system load produced by tasks with default user space prio.

Signed-off-by: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>
---
drivers/tty/tty_buffer.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c
index 18bd7f48a319..7cf42f6570a0 100644
--- a/drivers/tty/tty_buffer.c
+++ b/drivers/tty/tty_buffer.c
@@ -13,11 +13,13 @@
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/sched.h>
+#include <linux/sched/rt.h>
#include <linux/wait.h>
#include <linux/bitops.h>
#include <linux/delay.h>
#include <linux/module.h>
#include <linux/ratelimit.h>
+#include <uapi/linux/sched/types.h>


#define MIN_TTYB_SIZE 256
@@ -567,7 +569,15 @@ bool tty_buffer_queue_work(struct tty_port *port)

void tty_buffer_init_kthread(void)
{
- kthread_run(kthread_worker_fn, &tty_buffer_worker, "tty");
+ struct sched_param param = { .sched_priority = 1 };
+ struct task_struct *kworker_task;
+
+ kworker_task = kthread_run(kthread_worker_fn, &tty_buffer_worker, "tty");
+ if (IS_ERR(kworker_task)) {
+ pr_err("failed to create message pump task\n");
+ return;
+ }
+ sched_setscheduler(kworker_task, SCHED_FIFO, &param);
}

/**
--
2.19.1