Commit b13772f8 authored Oct 14, 2020 by Peter Zijlstra

sched/cpupri: Add CPUPRI_HIGHER

Add CPUPRI_HIGHER above the RT99 priority to denote the CPU is in use
by higher priority tasks (specifically deadline).

XXX: we should probably drive PUSH-PULL from cpupri, that would
automagically result in an RT-PUSH when DL sets cpupri to CPUPRI_HIGHER.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>

parent 934fc331

kernel/sched/cpupri.c

+9 −3

Original line number	Diff line number	Diff line
		@@ -11,7 +11,7 @@
		* This code tracks the priority of each CPU so that global migration
		* decisions are easy to calculate. Each CPU can be in a state as follows:
		*
		* (INVALID), NORMAL, RT1, ... RT99
		* (INVALID), NORMAL, RT1, ... RT99, HIGHER
		*
		* going from the lowest priority to the highest. CPUs in the INVALID state
		* are not eligible for routing. The system maintains this state with
		@@ -19,7 +19,7 @@
		* in that class). Therefore a typical application without affinity
		* restrictions can find a suitable CPU with O(1) complexity (e.g. two bit
		* searches). For tasks with affinity restrictions, the algorithm has a
		* worst case complexity of O(min(100, nr_domcpus)), though the scenario that
		* worst case complexity of O(min(101, nr_domcpus)), though the scenario that
		* yields the worst case search is fairly contrived.
		*/
		#include "sched.h"
		@@ -37,6 +37,8 @@
		* 50 49 49 50
		* ...
		* 99 0 0 99
		*
		* 100 100 (CPUPRI_HIGHER)
		*/
		static int convert_prio(int prio)
		{
		@@ -54,6 +56,10 @@ static int convert_prio(int prio)
		case MAX_RT_PRIO-1:
		cpupri = CPUPRI_NORMAL; /* 0 */
		break;

		case MAX_RT_PRIO:
		cpupri = CPUPRI_HIGHER; /* 100 */
		break;
		}

		return cpupri;
		@@ -195,7 +201,7 @@ int cpupri_find_fitness(struct cpupri cp, struct task_struct p,
		* cpupri_set - update the CPU priority setting
		* @cp: The cpupri context
		* @cpu: The target CPU
		* @newpri: The priority (INVALID-RT99) to assign to this CPU
		* @newpri: The priority (INVALID,NORMAL,RT1-RT99,HIGHER) to assign to this CPU
		*
		* Note: Assumes cpu_rq(cpu)->lock is locked
		*

kernel/sched/cpupri.h

+2 −1

Original line number	Diff line number	Diff line
		/* SPDX-License-Identifier: GPL-2.0 */

		#define CPUPRI_NR_PRIORITIES MAX_RT_PRIO
		#define CPUPRI_NR_PRIORITIES (MAX_RT_PRIO+1)

		#define CPUPRI_INVALID -1
		#define CPUPRI_NORMAL 0
		/* values 1-99 are for RT1-RT99 priorities */
		#define CPUPRI_HIGHER 100

		struct cpupri_vec {
		atomic_t count;

kernel/sched/deadline.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -1394,6 +1394,8 @@ static void inc_dl_deadline(struct dl_rq *dl_rq, u64 deadline)

		if (dl_rq->earliest_dl.curr == 0 \|\|
		dl_time_before(deadline, dl_rq->earliest_dl.curr)) {
		if (dl_rq->earliest_dl.curr == 0)
		cpupri_set(&rq->rd->cpupri, rq->cpu, CPUPRI_HIGHER);
		dl_rq->earliest_dl.curr = deadline;
		cpudl_set(&rq->rd->cpudl, rq->cpu, deadline);
		}
		@@ -1411,6 +1413,7 @@ static void dec_dl_deadline(struct dl_rq *dl_rq, u64 deadline)
		dl_rq->earliest_dl.curr = 0;
		dl_rq->earliest_dl.next = 0;
		cpudl_clear(&rq->rd->cpudl, rq->cpu);
		cpupri_set(&rq->rd->cpupri, rq->cpu, rq->rt.highest_prio.curr);
		} else {
		struct rb_node *leftmost = dl_rq->root.rb_leftmost;
		struct sched_dl_entity *entry;