linux-kernel - [RFC PATCH 6/6] sched/dl: Try not to select a too fast core

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20190506044836.2914-7-luca.abeni@santannapisa.it>
Date:   Mon,  6 May 2019 06:48:36 +0200
From:   Luca Abeni <luca.abeni@...tannapisa.it>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        "Paul E . McKenney" <paulmck@...ux.ibm.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Quentin Perret <quentin.perret@....com>,
        Luc Van Oostenryck <luc.vanoostenryck@...il.com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Patrick Bellasi <patrick.bellasi@....com>,
        Tommaso Cucinotta <tommaso.cucinotta@...tannapisa.it>,
        luca abeni <luca.abeni@...tannapisa.it>
Subject: [RFC PATCH 6/6] sched/dl: Try not to select a too fast core

From: luca abeni <luca.abeni@...tannapisa.it>

When a task can fit on multiple CPU cores, try to select the slowest
core that is able to properly serve the task. This avoids useless
future migrations, leaving the "fast cores" idle for more heavyweight
tasks.

Signed-off-by: luca abeni <luca.abeni@...tannapisa.it>
---
 kernel/sched/cpudeadline.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
index 2a4ac7b529b7..897ed71af515 100644
--- a/kernel/sched/cpudeadline.c
+++ b/kernel/sched/cpudeadline.c
@@ -143,17 +143,24 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
 	       struct cpumask *later_mask)
 {
 	const struct sched_dl_entity *dl_se = &p->dl;
+	struct cpumask tmp_mask;
 
 	if (later_mask &&
-	    cpumask_and(later_mask, cp->free_cpus, &p->cpus_allowed)) {
+	    cpumask_and(&tmp_mask, cp->free_cpus, &p->cpus_allowed)) {
 		int cpu, max_cpu = -1;
-		u64 max_cap = 0;
+		u64 max_cap = 0, min_cap = SCHED_CAPACITY_SCALE * SCHED_CAPACITY_SCALE;
 
-		for_each_cpu(cpu, later_mask) {
+		cpumask_clear(later_mask);
+		for_each_cpu(cpu, &tmp_mask) {
 			u64 cap;
 
-			if (!dl_task_fit(&p->dl, cpu, &cap))
-				cpumask_clear_cpu(cpu, later_mask);
+			if (dl_task_fit(&p->dl, cpu, &cap) && (cap <= min_cap)) {
+				if (cap < min_cap) {
+					min_cap = cap;
+					cpumask_clear(later_mask);
+				}
+				cpumask_set_cpu(cpu, later_mask);
+			}
 
 			if (cap > max_cap) {
 				max_cap = cap;
-- 
2.20.1