2015-04-01 09:03:35

by Lai Jiangshan

Subject: [PATCH] sched,nohz: fallback to housekeeping cpus before fallback to possible cpus

Let the processes which lose they original cpus run on housekeeping cpus
if they can to reduce disturbances on nohz_full cpus.

Cc: Thomas Gleixner <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: Kevin Hilman <[email protected]>
Cc: Mike Galbraith <[email protected]>
Cc: Viresh Kumar <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Signed-off-by: Lai Jiangshan <[email protected]>
---
kernel/sched/core.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index f0f831e..f9ef41a 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1286,7 +1286,7 @@ static int select_fallback_rq(int cpu, struct task_struct *p)
{
int nid = cpu_to_node(cpu);
const struct cpumask *nodemask = NULL;
- enum { cpuset, possible, fail } state = cpuset;
+ enum { cpuset, housekeeping, possible, fail } state = cpuset;
int dest_cpu;

/*
@@ -1322,8 +1322,15 @@ static int select_fallback_rq(int cpu, struct task_struct *p)
case cpuset:
/* No more Mr. Nice Guy. */
cpuset_cpus_allowed_fallback(p);
+ state = housekeeping;
+ break;
+
+ case housekeeping:
+#ifdef CONFIG_NO_HZ_FULL
+ do_set_cpus_allowed(p, housekeeping_mask);
state = possible;
break;
+# endif /* CONFIG_NO_HZ_FULL. Fallthrough when !CONFIG_NO_HZ_FULL */

case possible:
do_set_cpus_allowed(p, cpu_possible_mask);
--
2.1.0

2015-04-01 12:00:33

by Peter Zijlstra

Subject: Re: [PATCH] sched,nohz: fallback to housekeeping cpus before fallback to possible cpus

On Wed, Apr 01, 2015 at 05:06:12PM +0800, Lai Jiangshan wrote:
> Let the processes which lose they original cpus run on housekeeping cpus
> if they can to reduce disturbances on nohz_full cpus.

Its a fail if you get here in the first place, why should we fix that?